When the timer base is empty, base::next_expiry is set to base::clk +
NEXT_TIMER_MAX_DELTA and base::next_expiry_recalc is false. When no timer
is queued until jiffies reaches base::next_expiry value, the warning for
not finding any expired timer and base::next_expiry_recalc is false in
__run_timers() triggers.
To prevent triggering the warning in this valid scenario
base::timers_pending needs to be added to the warning condition.
Fixes: 31cd0e119d ("timers: Recalculate next timer interrupt only when necessary")
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20220405191732.7438-3-anna-maria@linutronix.de
This set of changes removes tracehook.h, moves modification of all of
the ptrace fields inside of siglock to remove races, adds a missing
permission check to ptrace.c
The removal of tracehook.h is quite significant as it has been a major
source of confusion in recent years. Much of that confusion was
around task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled
making the semantics clearer).
For people who don't know tracehook.h is a vestiage of an attempt to
implement uprobes like functionality that was never fully merged, and
was later superseeded by uprobes when uprobes was merged. For many
years now we have been removing what tracehook functionaly a little
bit at a time. To the point where now anything left in tracehook.h is
some weird strange thing that is difficult to understand.
Eric W. Biederman (15):
ptrace: Move ptrace_report_syscall into ptrace.h
ptrace/arm: Rename tracehook_report_syscall report_syscall
ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h
ptrace: Remove arch_syscall_{enter,exit}_tracehook
ptrace: Remove tracehook_signal_handler
task_work: Remove unnecessary include from posix_timers.h
task_work: Introduce task_work_pending
task_work: Call tracehook_notify_signal from get_signal on all architectures
task_work: Decouple TIF_NOTIFY_SIGNAL and task_work
signal: Move set_notify_signal and clear_notify_signal into sched/signal.h
resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume
resume_user_mode: Move to resume_user_mode.h
tracehook: Remove tracehook.h
ptrace: Move setting/clearing ptrace_message into ptrace_stop
ptrace: Return the signal to continue with from ptrace_stop
Jann Horn (1):
ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE
Yang Li (1):
ptrace: Remove duplicated include in ptrace.c
MAINTAINERS | 1 -
arch/Kconfig | 5 +-
arch/alpha/kernel/ptrace.c | 5 +-
arch/alpha/kernel/signal.c | 4 +-
arch/arc/kernel/ptrace.c | 5 +-
arch/arc/kernel/signal.c | 4 +-
arch/arm/kernel/ptrace.c | 12 +-
arch/arm/kernel/signal.c | 4 +-
arch/arm64/kernel/ptrace.c | 14 +--
arch/arm64/kernel/signal.c | 4 +-
arch/csky/kernel/ptrace.c | 5 +-
arch/csky/kernel/signal.c | 4 +-
arch/h8300/kernel/ptrace.c | 5 +-
arch/h8300/kernel/signal.c | 4 +-
arch/hexagon/kernel/process.c | 4 +-
arch/hexagon/kernel/signal.c | 1 -
arch/hexagon/kernel/traps.c | 6 +-
arch/ia64/kernel/process.c | 4 +-
arch/ia64/kernel/ptrace.c | 6 +-
arch/ia64/kernel/signal.c | 1 -
arch/m68k/kernel/ptrace.c | 5 +-
arch/m68k/kernel/signal.c | 4 +-
arch/microblaze/kernel/ptrace.c | 5 +-
arch/microblaze/kernel/signal.c | 4 +-
arch/mips/kernel/ptrace.c | 5 +-
arch/mips/kernel/signal.c | 4 +-
arch/nds32/include/asm/syscall.h | 2 +-
arch/nds32/kernel/ptrace.c | 5 +-
arch/nds32/kernel/signal.c | 4 +-
arch/nios2/kernel/ptrace.c | 5 +-
arch/nios2/kernel/signal.c | 4 +-
arch/openrisc/kernel/ptrace.c | 5 +-
arch/openrisc/kernel/signal.c | 4 +-
arch/parisc/kernel/ptrace.c | 7 +-
arch/parisc/kernel/signal.c | 4 +-
arch/powerpc/kernel/ptrace/ptrace.c | 8 +-
arch/powerpc/kernel/signal.c | 4 +-
arch/riscv/kernel/ptrace.c | 5 +-
arch/riscv/kernel/signal.c | 4 +-
arch/s390/include/asm/entry-common.h | 1 -
arch/s390/kernel/ptrace.c | 1 -
arch/s390/kernel/signal.c | 5 +-
arch/sh/kernel/ptrace_32.c | 5 +-
arch/sh/kernel/signal_32.c | 4 +-
arch/sparc/kernel/ptrace_32.c | 5 +-
arch/sparc/kernel/ptrace_64.c | 5 +-
arch/sparc/kernel/signal32.c | 1 -
arch/sparc/kernel/signal_32.c | 4 +-
arch/sparc/kernel/signal_64.c | 4 +-
arch/um/kernel/process.c | 4 +-
arch/um/kernel/ptrace.c | 5 +-
arch/x86/kernel/ptrace.c | 1 -
arch/x86/kernel/signal.c | 5 +-
arch/x86/mm/tlb.c | 1 +
arch/xtensa/kernel/ptrace.c | 5 +-
arch/xtensa/kernel/signal.c | 4 +-
block/blk-cgroup.c | 2 +-
fs/coredump.c | 1 -
fs/exec.c | 1 -
fs/io-wq.c | 6 +-
fs/io_uring.c | 11 +-
fs/proc/array.c | 1 -
fs/proc/base.c | 1 -
include/asm-generic/syscall.h | 2 +-
include/linux/entry-common.h | 47 +-------
include/linux/entry-kvm.h | 2 +-
include/linux/posix-timers.h | 1 -
include/linux/ptrace.h | 81 ++++++++++++-
include/linux/resume_user_mode.h | 64 ++++++++++
include/linux/sched/signal.h | 17 +++
include/linux/task_work.h | 5 +
include/linux/tracehook.h | 226 -----------------------------------
include/uapi/linux/ptrace.h | 2 +-
kernel/entry/common.c | 19 +--
kernel/entry/kvm.c | 9 +-
kernel/exit.c | 3 +-
kernel/livepatch/transition.c | 1 -
kernel/ptrace.c | 47 +++++---
kernel/seccomp.c | 1 -
kernel/signal.c | 62 +++++-----
kernel/task_work.c | 4 +-
kernel/time/posix-cpu-timers.c | 1 +
mm/memcontrol.c | 2 +-
security/apparmor/domain.c | 1 -
security/selinux/hooks.c | 1 -
85 files changed, 372 insertions(+), 495 deletions(-)
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Merge tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull ptrace cleanups from Eric Biederman:
"This set of changes removes tracehook.h, moves modification of all of
the ptrace fields inside of siglock to remove races, adds a missing
permission check to ptrace.c
The removal of tracehook.h is quite significant as it has been a major
source of confusion in recent years. Much of that confusion was around
task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled making the
semantics clearer).
For people who don't know tracehook.h is a vestiage of an attempt to
implement uprobes like functionality that was never fully merged, and
was later superseeded by uprobes when uprobes was merged. For many
years now we have been removing what tracehook functionaly a little
bit at a time. To the point where anything left in tracehook.h was
some weird strange thing that was difficult to understand"
* tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
ptrace: Remove duplicated include in ptrace.c
ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE
ptrace: Return the signal to continue with from ptrace_stop
ptrace: Move setting/clearing ptrace_message into ptrace_stop
tracehook: Remove tracehook.h
resume_user_mode: Move to resume_user_mode.h
resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume
signal: Move set_notify_signal and clear_notify_signal into sched/signal.h
task_work: Decouple TIF_NOTIFY_SIGNAL and task_work
task_work: Call tracehook_notify_signal from get_signal on all architectures
task_work: Introduce task_work_pending
task_work: Remove unnecessary include from posix_timers.h
ptrace: Remove tracehook_signal_handler
ptrace: Remove arch_syscall_{enter,exit}_tracehook
ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h
ptrace/arm: Rename tracehook_report_syscall report_syscall
ptrace: Move ptrace_report_syscall into ptrace.h
The tasklist_lock popped up as a scalability bottleneck on some testing
workloads. The readlocks in do_prlimit and set/getpriority are not
necessary in all cases.
Based on a cycles profile, it looked like ~87% of the time was spent in
the kernel, ~42% of which was just trying to get *some* spinlock
(queued_spin_lock_slowpath, not necessarily the tasklist_lock).
The big offenders (with rough percentages in cycles of the overall trace):
- do_wait 11%
- setpriority 8% (this patchset)
- kill 8%
- do_exit 5%
- clone 3%
- prlimit64 2% (this patchset)
- getrlimit 1% (this patchset)
I can't easily test this patchset on the original workload for various
reasons. Instead, I used the microbenchmark below to at least verify
there was some improvement. This patchset had a 28% speedup (12% from
baseline to set/getprio, then another 14% for prlimit).
One interesting thing is that my libc's getrlimit() was calling
prlimit64, so hoisting the read_lock(tasklist_lock) into sys_prlimit64
had no effect - it essentially optimized the older syscalls only. I
didn't do that in this patchset, but figured I'd mention it since it was
an option from the previous patch's discussion.
v3: https://lkml.kernel.org/r/20220106172041.522167-1-brho@google.com
v2: https://lore.kernel.org/lkml/20220105212828.197013-1-brho@google.com/
- update_rlimit_cpu on the group_leader instead of for_each_thread.
- update_rlimit_cpu still returns 0 or -ESRCH, even though we don't care
about the error here. it felt safer that way in case someone uses
that function again.
v1: https://lore.kernel.org/lkml/20211213220401.1039578-1-brho@google.com/
int main(int argc, char **argv)
{
pid_t child;
struct rlimit rlim[1];
fork(); fork(); fork(); fork(); fork(); fork();
for (int i = 0; i < 5000; i++) {
child = fork();
if (child < 0)
exit(1);
if (child > 0) {
usleep(1000);
kill(child, SIGTERM);
waitpid(child, NULL, 0);
} else {
for (;;) {
setpriority(PRIO_PROCESS, 0,
getpriority(PRIO_PROCESS, 0));
getrlimit(RLIMIT_CPU, rlim);
}
}
}
return 0;
}
Barret Rhoden (3):
setpriority: only grab the tasklist_lock for PRIO_PGRP
prlimit: make do_prlimit() static
prlimit: do not grab the tasklist_lock
include/linux/posix-timers.h | 2 +-
include/linux/resource.h | 2 -
kernel/sys.c | 127 +++++++++++++++++----------------
kernel/time/posix-cpu-timers.c | 12 +++-
4 files changed, 76 insertions(+), 67 deletions(-)
I have dropped the first change in this series as an almost identical
change was merged as commit 7f8ca0edfe ("kernel/sys.c: only take
tasklist_lock for get/setpriority(PRIO_PGRP)").
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
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Merge tag 'prlimit-tasklist_lock-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull tasklist_lock optimizations from Eric Biederman:
"prlimit and getpriority tasklist_lock optimizations
The tasklist_lock popped up as a scalability bottleneck on some
testing workloads. The readlocks in do_prlimit and set/getpriority are
not necessary in all cases.
Based on a cycles profile, it looked like ~87% of the time was spent
in the kernel, ~42% of which was just trying to get *some* spinlock
(queued_spin_lock_slowpath, not necessarily the tasklist_lock).
The big offenders (with rough percentages in cycles of the overall
trace):
- do_wait 11%
- setpriority 8% (done previously in commit 7f8ca0edfe)
- kill 8%
- do_exit 5%
- clone 3%
- prlimit64 2% (this patchset)
- getrlimit 1% (this patchset)
I can't easily test this patchset on the original workload for various
reasons. Instead, I used the microbenchmark below to at least verify
there was some improvement. This patchset had a 28% speedup (12% from
baseline to set/getprio, then another 14% for prlimit).
This series used to do the setpriority case, but an almost identical
change was merged as commit 7f8ca0edfe ("kernel/sys.c: only take
tasklist_lock for get/setpriority(PRIO_PGRP)") so that has been
dropped from here.
One interesting thing is that my libc's getrlimit() was calling
prlimit64, so hoisting the read_lock(tasklist_lock) into sys_prlimit64
had no effect - it essentially optimized the older syscalls only. I
didn't do that in this patchset, but figured I'd mention it since it
was an option from the previous patch's discussion"
micobenchmark.c:
---------------
int main(int argc, char **argv)
{
pid_t child;
struct rlimit rlim[1];
fork(); fork(); fork(); fork(); fork(); fork();
for (int i = 0; i < 5000; i++) {
child = fork();
if (child < 0)
exit(1);
if (child > 0) {
usleep(1000);
kill(child, SIGTERM);
waitpid(child, NULL, 0);
} else {
for (;;) {
setpriority(PRIO_PROCESS, 0,
getpriority(PRIO_PROCESS, 0));
getrlimit(RLIMIT_CPU, rlim);
}
}
}
return 0;
}
Link: https://lore.kernel.org/lkml/20211213220401.1039578-1-brho@google.com/ [v1]
Link: https://lore.kernel.org/lkml/20220105212828.197013-1-brho@google.com/ [v2]
Link: https://lore.kernel.org/lkml/20220106172041.522167-1-brho@google.com/ [v3]
* tag 'prlimit-tasklist_lock-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
prlimit: do not grab the tasklist_lock
prlimit: make do_prlimit() static
Break a header file circular dependency by removing the unnecessary
include of task_work.h from posix_timers.h.
sched.h -> posix-timers.h
posix-timers.h -> task_work.h
task_work.h -> sched.h
Add missing includes of task_work.h to:
arch/x86/mm/tlb.c
kernel/time/posix-cpu-timers.c
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-6-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Unnecessarily grabbing the tasklist_lock can be a scalability bottleneck
for workloads that also must grab the tasklist_lock for waiting,
killing, and cloning.
The tasklist_lock was grabbed to protect tsk->sighand from disappearing
(becoming NULL). tsk->signal was already protected by holding a
reference to tsk.
update_rlimit_cpu() assumed tsk->sighand != NULL. With this commit, it
attempts to lock_task_sighand(). However, this means that
update_rlimit_cpu() can fail. This only happens when a task is exiting.
Note that during exec, sighand may *change*, but it will not be NULL.
Prior to this commit, the do_prlimit() ensured that update_rlimit_cpu()
would not fail by read locking the tasklist_lock and checking tsk->sighand
!= NULL.
If update_rlimit_cpu() fails, there may be other tasks that are not
exiting that share tsk->signal. However, the group_leader is the last
task to be released, so if we cannot update_rlimit_cpu(group_leader),
then the entire process is exiting.
The only other caller of update_rlimit_cpu() is
selinux_bprm_committing_creds(). It has tsk == current, so
update_rlimit_cpu() cannot fail (current->sighand cannot disappear
until current exits).
This change resulted in a 14% speedup on a microbenchmark where parents
kill and wait on their children, and children getpriority, setpriority,
and getrlimit.
Signed-off-by: Barret Rhoden <brho@google.com>
Link: https://lkml.kernel.org/r/20220106172041.522167-4-brho@google.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
RCU_SOFTIRQ used to be special in that it could be raised on purpose
within the idle path to prevent from stopping the tick. Some code still
prevents from unnecessary warnings related to this specific behaviour
while entering in dynticks-idle mode.
However the nohz layout has changed quite a bit in ten years, and the
removal of CONFIG_RCU_FAST_NO_HZ has been the final straw to this
safe-conduct. Now the RCU_SOFTIRQ vector is expected to be raised from
sane places.
A remaining corner case is admitted though when the vector is invoked
in fragile hotplug path.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
With the removal of CONFIG_RCU_FAST_NO_HZ, the parameters in
rcu_needs_cpu() are not necessary anymore. Simply remove them.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
On some rare cases, the timekeeper CPU may be delaying its jiffies
update duty for a while. Known causes include:
* The timekeeper is waiting on stop_machine in a MULTI_STOP_DISABLE_IRQ
or MULTI_STOP_RUN state. Disabled interrupts prevent from timekeeping
updates while waiting for the target CPU to complete its
stop_machine() callback.
* The timekeeper vcpu has VMEXIT'ed for a long while due to some overload
on the host.
Detect and fix these situations with emergency timekeeping catchups.
Original-patch-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
A watchdog maximum skew of 100us may still be too small for
some systems or archs. It may also be too small when some kernel
debug config options are enabled. So add a new Kconfig option
CLOCKSOURCE_WATCHDOG_MAX_SKEW_US to allow kernel builders to have more
control on the threshold for marking clocksource as unstable.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Merge tag 'bitmap-5.17-rc1' of git://github.com/norov/linux
Pull bitmap updates from Yury Norov:
- introduce for_each_set_bitrange()
- use find_first_*_bit() instead of find_next_*_bit() where possible
- unify for_each_bit() macros
* tag 'bitmap-5.17-rc1' of git://github.com/norov/linux:
vsprintf: rework bitmap_list_string
lib: bitmap: add performance test for bitmap_print_to_pagebuf
bitmap: unify find_bit operations
mm/percpu: micro-optimize pcpu_is_populated()
Replace for_each_*_bit_from() with for_each_*_bit() where appropriate
find: micro-optimize for_each_{set,clear}_bit()
include/linux: move for_each_bit() macros from bitops.h to find.h
cpumask: replace cpumask_next_* with cpumask_first_* where appropriate
tools: sync tools/bitmap with mother linux
all: replace find_next{,_zero}_bit with find_first{,_zero}_bit where appropriate
cpumask: use find_first_and_bit()
lib: add find_first_and_bit()
arch: remove GENERIC_FIND_FIRST_BIT entirely
include: move find.h from asm_generic to linux
bitops: move find_bit_*_le functions from le.h to find.h
bitops: protect find_first_{,zero}_bit properly
cpumask_first() is a more effective analogue of 'next' version if n == -1
(which means start == 0). This patch replaces 'next' with 'first' where
things look trivial.
There's no cpumask_first_zero() function, so create it.
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Core:
- Make the clocksource watchdog more robust by better validation checks
of the measurement.
Drivers:
- New drivers for MStar and SSD20xd SOCs
- The usual cleanups and improvements all over the place
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Merge tag 'timers-core-2022-01-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Updates for the time(r) subsystem:
Core:
- Make the clocksource watchdog more robust by better validation
checks of the measurement.
Drivers:
- New drivers for MStar and SSD20xd SOCs
- The usual cleanups and improvements all over the place"
* tag 'timers-core-2022-01-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
dt-bindings: timer: Add Mstar MSC313e timer devicetree bindings documentation
clocksource/drivers/msc313e: Add support for ssd20xd-based platforms
clocksource/drivers: Add MStar MSC313e timer support
clocksource/drivers/pistachio: Fix -Wunused-but-set-variable warning
clocksource/drivers/timer-imx-sysctr: Set cpumask to cpu_possible_mask
clocksource/drivers/imx-sysctr: Mark two variable with __ro_after_init
clocksource/drivers/renesas,ostm: Make RENESAS_OSTM symbol visible
clocksource/drivers/renesas-ostm: Add RZ/G2L OSTM support
dt-bindings: timer: renesas: ostm: Document Renesas RZ/G2L OSTM
clocksource/drivers/exynos_mct: Fix silly typo resulting in checkpatch warning
clocksource: Reduce the default clocksource_watchdog() retries to 2
clocksource: Avoid accidental unstable marking of clocksources
dt-bindings: timer: tpm-timer: Add imx8ulp compatible string
reset: Add of_reset_control_get_optional_exclusive()
clocksource/drivers/exynos_mct: Refactor resources allocation
dt-bindings: timer: remove rockchip,rk3066-timer compatible string from rockchip,rk-timer.yaml
dt-bindings: timer: cadence_ttc: Add power-domains
Pull clocksource watchdog updates from Paul McKenney:
- Avoid accidental unstable marking of clocksources by rejecting
clocksource measurements where the source of the skew is the delay
reading reference clocksource itself. This change avoids many of the
current false positives caused by epic cache-thrashing workloads.
- Reduce the default clocksource_watchdog() retries to 2, thus offsetting
the increased overhead due to #1 above rereading the reference
clocksource.
Link: https://lore.kernel.org/lkml/20220105001723.GA536708@paulmck-ThinkPad-P17-Gen-1
Even after commit e1d7ba8735 ("time: Always make sure wall_to_monotonic
isn't positive") it is still possible to make wall_to_monotonic positive
by running the following code:
int main(void)
{
struct timespec time;
clock_gettime(CLOCK_MONOTONIC, &time);
time.tv_nsec = 0;
clock_settime(CLOCK_REALTIME, &time);
return 0;
}
The reason is that the second parameter of timespec64_compare(), ts_delta,
may be unnormalized because the delta is calculated with an open coded
substraction which causes the comparison of tv_sec to yield the wrong
result:
wall_to_monotonic = { .tv_sec = -10, .tv_nsec = 900000000 }
ts_delta = { .tv_sec = -9, .tv_nsec = -900000000 }
That makes timespec64_compare() claim that wall_to_monotonic < ts_delta,
but actually the result should be wall_to_monotonic > ts_delta.
After normalization, the result of timespec64_compare() is correct because
the tv_sec comparison is not longer misleading:
wall_to_monotonic = { .tv_sec = -10, .tv_nsec = 900000000 }
ts_delta = { .tv_sec = -10, .tv_nsec = 100000000 }
Use timespec64_sub() to ensure that ts_delta is normalized, which fixes the
issue.
Fixes: e1d7ba8735 ("time: Always make sure wall_to_monotonic isn't positive")
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211213135727.1656662-1-liaoyu15@huawei.com
Patch series "mm/damon: Fix fake /proc/loadavg reports", v3.
This patchset fixes DAMON's fake load report issue. The first patch
makes yet another variant of usleep_range() for this fix, and the second
patch fixes the issue of DAMON by making it using the newly introduced
function.
This patch (of 2):
Some kernel threads such as DAMON could need to repeatedly sleep in
micro seconds level. Because usleep_range() sleeps in uninterruptible
state, however, such threads would make /proc/loadavg reports fake load.
To help such cases, this commit implements a variant of usleep_range()
called usleep_idle_range(). It is same to usleep_range() but sets the
state of the current task as TASK_IDLE while sleeping.
Link: https://lkml.kernel.org/r/20211126145015.15862-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211126145015.15862-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: John Stultz <john.stultz@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When at least one CPU runs in nohz_full mode, a dedicated timekeeper CPU
is guaranteed to stay online and to never stop its tick.
Meanwhile on some rare case, the dedicated timekeeper may be running
with interrupts disabled for a while, such as in stop_machine.
If jiffies stop being updated, a nohz_full CPU may end up endlessly
programming the next tick in the past, taking the last jiffies update
monotonic timestamp as a stale base, resulting in an tick storm.
Here is a scenario where it matters:
0) CPU 0 is the timekeeper and CPU 1 a nohz_full CPU.
1) A stop machine callback is queued to execute somewhere.
2) CPU 0 reaches MULTI_STOP_DISABLE_IRQ while CPU 1 is still in
MULTI_STOP_PREPARE. Hence CPU 0 can't do its timekeeping duty. CPU 1
can still take IRQs.
3) CPU 1 receives an IRQ which queues a timer callback one jiffy forward.
4) On IRQ exit, CPU 1 schedules the tick one jiffy forward, taking
last_jiffies_update as a base. But last_jiffies_update hasn't been
updated for 2 jiffies since the timekeeper has interrupts disabled.
5) clockevents_program_event(), which relies on ktime_get(), observes
that the expiration is in the past and therefore programs the min
delta event on the clock.
6) The tick fires immediately, goto 3)
7) Tick storm, the nohz_full CPU is drown and takes ages to reach
MULTI_STOP_DISABLE_IRQ, which is the only way out of this situation.
Solve this with unconditionally updating jiffies if the value is stale
on nohz_full IRQ entry. IRQs and other disturbances are expected to be
rare enough on nohz_full for the unconditional call to ktime_get() to
actually matter.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20211026141055.57358-2-frederic@kernel.org
With the previous patch, there is an extra watchdog read in each retry.
Now the total number of clocksource reads is increased to 4 per iteration.
In order to avoid increasing the clock skew check overhead, the default
maximum number of retries is reduced from 3 to 2 to maintain the same 12
clocksource reads in the worst case.
Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Since commit db3a34e174 ("clocksource: Retry clock read if long delays
detected") and commit 2e27e793e2 ("clocksource: Reduce clocksource-skew
threshold"), it is found that tsc clocksource fallback to hpet can
sometimes happen on both Intel and AMD systems especially when they are
running stressful benchmarking workloads. Of the 23 systems tested with
a v5.14 kernel, 10 of them have switched to hpet clock source during
the test run.
The result of falling back to hpet is a drastic reduction of performance
when running benchmarks. For example, the fio performance tests can
drop up to 70% whereas the iperf3 performance can drop up to 80%.
4 hpet fallbacks happened during bootup. They were:
[ 8.749399] clocksource: timekeeping watchdog on CPU13: hpet read-back delay of 263750ns, attempt 4, marking unstable
[ 12.044610] clocksource: timekeeping watchdog on CPU19: hpet read-back delay of 186166ns, attempt 4, marking unstable
[ 17.336941] clocksource: timekeeping watchdog on CPU28: hpet read-back delay of 182291ns, attempt 4, marking unstable
[ 17.518565] clocksource: timekeeping watchdog on CPU34: hpet read-back delay of 252196ns, attempt 4, marking unstable
Other fallbacks happen when the systems were running stressful
benchmarks. For example:
[ 2685.867873] clocksource: timekeeping watchdog on CPU117: hpet read-back delay of 57269ns, attempt 4, marking unstable
[46215.471228] clocksource: timekeeping watchdog on CPU8: hpet read-back delay of 61460ns, attempt 4, marking unstable
Commit 2e27e793e2 ("clocksource: Reduce clocksource-skew threshold"),
changed the skew margin from 100us to 50us. I think this is too small
and can easily be exceeded when running some stressful workloads on a
thermally stressed system. So it is switched back to 100us.
Even a maximum skew margin of 100us may be too small in for some systems
when booting up especially if those systems are under thermal stress. To
eliminate the case that the large skew is due to the system being too
busy slowing down the reading of both the watchdog and the clocksource,
an extra consecutive read of watchdog clock is being done to check this.
The consecutive watchdog read delay is compared against
WATCHDOG_MAX_SKEW/2. If the delay exceeds the limit, we assume that
the system is just too busy. A warning will be printed to the console
and the clock skew check is skipped for this round.
Fixes: db3a34e174 ("clocksource: Retry clock read if long delays detected")
Fixes: 2e27e793e2 ("clocksource: Reduce clocksource-skew threshold")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
copy_process currently copies task_struct.posix_cputimers_work as-is. If a
timer interrupt arrives while handling clone and before dup_task_struct
completes then the child task will have:
1. posix_cputimers_work.scheduled = true
2. posix_cputimers_work.work queued.
copy_process clears task_struct.task_works, so (2) will have no effect and
posix_cpu_timers_work will never run (not to mention it doesn't make sense
for two tasks to share a common linked list).
Since posix_cpu_timers_work never runs, posix_cputimers_work.scheduled is
never cleared. Since scheduled is set, future timer interrupts will skip
scheduling work, with the ultimate result that the task will never receive
timer expirations.
Together, the complete flow is:
1. Task 1 calls clone(), enters kernel.
2. Timer interrupt fires, schedules task work on Task 1.
2a. task_struct.posix_cputimers_work.scheduled = true
2b. task_struct.posix_cputimers_work.work added to
task_struct.task_works.
3. dup_task_struct() copies Task 1 to Task 2.
4. copy_process() clears task_struct.task_works for Task 2.
5. Future timer interrupts on Task 2 see
task_struct.posix_cputimers_work.scheduled = true and skip scheduling
work.
Fix this by explicitly clearing contents of task_struct.posix_cputimers_work
in copy_process(). This was never meant to be shared or inherited across
tasks in the first place.
Fixes: 1fb497dd00 ("posix-cpu-timers: Provide mechanisms to defer timer handling to task_work")
Reported-by: Rhys Hiltner <rhys@justin.tv>
Signed-off-by: Michael Pratt <mpratt@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20211101210615.716522-1-mpratt@google.com
Resetting/stopping an itimer eventually leads to it being reprogrammed
with an actual "0" value. As a result the itimer expires on the next
tick, triggering an unexpected signal.
To fix this, make sure that
struct signal_struct::it[CPUCLOCK_PROF/VIRT]::expires is set to 0 when
setitimer() passes a 0 it_value, indicating that the timer must stop.
Fixes: 406dd42bd1 ("posix-cpu-timers: Force next expiration recalc after itimer reset")
Reported-by: Victor Stinner <vstinner@redhat.com>
Reported-by: Chris Hixon <linux-kernel-bugs@hixontech.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210913145332.232023-1-frederic@kernel.org
Merge misc updates from Andrew Morton:
"173 patches.
Subsystems affected by this series: ia64, ocfs2, block, and mm (debug,
pagecache, gup, swap, shmem, memcg, selftests, pagemap, mremap,
bootmem, sparsemem, vmalloc, kasan, pagealloc, memory-failure,
hugetlb, userfaultfd, vmscan, compaction, mempolicy, memblock,
oom-kill, migration, ksm, percpu, vmstat, and madvise)"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (173 commits)
mm/madvise: add MADV_WILLNEED to process_madvise()
mm/vmstat: remove unneeded return value
mm/vmstat: simplify the array size calculation
mm/vmstat: correct some wrong comments
mm/percpu,c: remove obsolete comments of pcpu_chunk_populated()
selftests: vm: add COW time test for KSM pages
selftests: vm: add KSM merging time test
mm: KSM: fix data type
selftests: vm: add KSM merging across nodes test
selftests: vm: add KSM zero page merging test
selftests: vm: add KSM unmerge test
selftests: vm: add KSM merge test
mm/migrate: correct kernel-doc notation
mm: wire up syscall process_mrelease
mm: introduce process_mrelease system call
memblock: make memblock_find_in_range method private
mm/mempolicy.c: use in_task() in mempolicy_slab_node()
mm/mempolicy: unify the create() func for bind/interleave/prefer-many policies
mm/mempolicy: advertise new MPOL_PREFERRED_MANY
mm/hugetlb: add support for mempolicy MPOL_PREFERRED_MANY
...
A program may create multiple interval timers using timer_create(). For
each timer the kernel preallocates a "queued real-time signal",
Consequently, the number of timers is limited by the RLIMIT_SIGPENDING
resource limit. The allocated object is quite small, ~250 bytes, but even
the default signal limits allow to consume up to 100 megabytes per user.
It makes sense to account for them to limit the host's memory consumption
from inside the memcg-limited container.
Link: https://lkml.kernel.org/r/57795560-025c-267c-6b1a-dea852d95530@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yutian Yang <nglaive@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Container admin can create new namespaces and force kernel to allocate up
to several pages of memory for the namespaces and its associated
structures.
Net and uts namespaces have enabled accounting for such allocations. It
makes sense to account for rest ones to restrict the host's memory
consumption from inside the memcg-limited container.
Link: https://lkml.kernel.org/r/5525bcbf-533e-da27-79b7-158686c64e13@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Yutian Yang <nglaive@gmail.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The clocksource watchdog test sets a local JIFFIES_SHIFT macro and assumes
that HZ is >= 100. For smaller HZ values this shift value is too large and
causes undefined behaviour.
Move the HZ-based definitions of JIFFIES_SHIFT from kernel/time/jiffies.c
to kernel/time/tick-internal.h so the clocksource watchdog test can utilize
them, which makes it work correctly with all HZ values.
[ tglx: Resolved conflicts and massaged changelog ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/20210812000133.GA402890@paulmck-ThinkPad-P17-Gen-1/
Since the recent consoliation of reprogramming functions,
hrtimer_force_reprogram() is affected by a check whether the new expiry
time is past the current expiry time.
This breaks the NOHZ logic as that relies on the fact that the tick hrtimer
is moved into the future. That means cpu_base->expires_next becomes stale
and subsequent reprogramming attempts fail as well until the situation is
cleaned up by an hrtimer interrupts.
For some yet unknown reason this leads to a complete stall, so for now
partially revert the offending commit to a known working state. The root
cause for the stall is still investigated and will be fixed in a subsequent
commit.
Fixes: b14bca97c9 ("hrtimer: Consolidate reprogramming code")
Reported-by: Mike Galbraith <efault@gmx.de>
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Mike Galbraith <efault@gmx.de>
Link: https://lore.kernel.org/r/8735recskh.ffs@tglx
clock_was_set() can be invoked from preemptible context. Use raw_cpu_ptr()
to check whether high resolution mode is active or not. It does not matter
whether the task migrates after acquiring the pointer.
Fixes: e71a4153b7 ("hrtimer: Force clock_was_set() handling for the HIGHRES=n, NOHZ=y case")
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/875ywacsmb.ffs@tglx
By unconditionally updating the offsets there are more indicators
whether the SMP function calls on clock_was_set() can be avoided:
- When the offset update already happened on the remote CPU then the
remote update attempt will yield the same seqeuence number and no
IPI is required.
- When the remote CPU is currently handling hrtimer_interrupt(). In
that case the remote CPU will reevaluate the timer bases before
reprogramming anyway, so nothing to do.
- After updating it can be checked whether the first expiring timer in
the affected clock bases moves before the first expiring (softirq)
timer of the CPU. If that's not the case then sending the IPI is not
required.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.887322464@linutronix.de
Setting of clocks triggers an unconditional SMP function call on all online
CPUs to reprogram the clock event device.
However, only some clocks have their offsets updated and therefore
potentially require a reprogram. That's CLOCK_REALTIME and CLOCK_TAI and in
the case of resume (delayed sleep time injection) also CLOCK_BOOTTIME.
Instead of sending an IPI unconditionally, check each per CPU hrtimer base
whether it has active timers in the affected clock bases which are
indicated by the caller in the @bases argument of clock_was_set().
If that's not the case, skip the IPI and update the offsets remotely which
ensures that any subsequently armed timers on the affected clocks are
evaluated with the correct offsets.
[ tglx: Adopted to the new bases argument, removed the softirq_active
check, added comment, fixed up stale comment ]
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.787536542@linutronix.de
clock_was_set() unconditionaly invokes retrigger_next_event() on all online
CPUs. This was necessary because that mechanism was also used for resume
from suspend to idle which is not longer the case.
The bases arguments allows the callers of clock_was_set() to hand in a mask
which tells clock_was_set() which of the hrtimer clock bases are affected
by the clock setting. This mask will be used in the next step to check
whether a CPU base has timers queued on a clock base affected by the event
and avoid the SMP function call if there are none.
Add a @bases argument, provide defines for the active bases masking and
fixup all callsites.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.691083465@linutronix.de
do_adjtimex() might end up scheduling a delayed clock_was_set() via
timekeeping_advance() and then invoke clock_was_set() directly which is
pointless.
Make timekeeping_advance() return whether an invocation of clock_was_set()
is required and handle it at the call sites which allows do_adjtimex() to
issue a single direct call if required.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.580966888@linutronix.de
Resuming timekeeping is a clock-was-set event and uses the clock-was-set
notification mechanism. This is in the way of making the clock-was-set
update for hrtimers selective so unnecessary IPIs are avoided when a CPU
base does not have timers queued which are affected by the clock setting.
Distangle it by invoking hrtimer_resume() on each unfreezing CPU and invoke
the new timerfd_resume() function from timekeeping_resume() which is the
only place where this is needed.
Rename hrtimer_resume() to hrtimer_resume_local() to reflect the change.
With this the clock_was_set*() functions are not longer required to IPI all
CPUs unconditionally and can get some smarts to avoid them.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.488853478@linutronix.de
When CONFIG_HIGH_RES_TIMERS is disabled, but NOHZ is enabled then
clock_was_set() is not doing anything. With HIGHRES=n the kernel relies on
the periodic tick to update the clock offsets, but when NOHZ is enabled and
active then CPUs which are in a deep idle sleep do not have a periodic tick
which means the expiry of timers affected by clock_was_set() can be
arbitrarily delayed up to the point where the CPUs are brought out of idle
again.
Make the clock_was_set() logic unconditionaly available so that idle CPUs
are kicked out of idle to handle the update.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.288697903@linutronix.de
If high resolution timers are disabled the timerfd notification about a
clock was set event is not happening for all cases which use
clock_was_set_delayed() because that's a NOP for HIGHRES=n, which is wrong.
Make clock_was_set_delayed() unconditially available to fix that.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.196661266@linutronix.de
This code is mostly duplicated. The redudant store in the force reprogram
case does no harm and the in hrtimer interrupt condition cannot be true for
the force reprogram invocations.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.054424875@linutronix.de
If __hrtimer_start_range_ns() is invoked with an already armed hrtimer then
the timer has to be canceled first and then added back. If the timer is the
first expiring timer then on removal the clockevent device is reprogrammed
to the next expiring timer to avoid that the pending expiry fires needlessly.
If the new expiry time ends up to be the first expiry again then the clock
event device has to reprogrammed again.
Avoid this by checking whether the timer is the first to expire and in that
case, keep the timer on the current CPU and delay the reprogramming up to
the point where the timer has been enqueued again.
Reported-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135157.873137732@linutronix.de
There are several scenarios that can result in posix_cpu_timer_set()
not queueing the timer but still leaving the threadgroup cputime counter
running or keeping the tick dependency around for a random amount of time.
1) If timer_settime() is called with a 0 expiration on a timer that is
already disabled, the process wide cputime counter will be started
and won't ever get a chance to be stopped by stop_process_timer()
since no timer is actually armed to be processed.
The following snippet is enough to trigger the issue.
void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };
timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
timer_settime(id, TIMER_ABSTIME, &val, NULL);
timer_delete(id);
}
2) If timer_settime() is called with a 0 expiration on a timer that is
already armed, the timer is dequeued but not really disarmed. So the
process wide cputime counter and the tick dependency may still remain
a while around.
The following code snippet keeps this overhead around for one week after
the timer deletion:
void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };
val.it_value.tv_sec = 604800;
timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
timer_settime(id, 0, &val, NULL);
timer_delete(id);
}
3) If the timer was initially deactivated, this call to timer_settime()
with an early expiration may have started the process wide cputime
counter even though the timer hasn't been queued and armed because it
has fired early and inline within posix_cpu_timer_set() itself. As a
result the process wide cputime counter may never stop until a new
timer is ever armed in the future.
The following code snippet can reproduce this:
void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };
signal(SIGALRM, SIG_IGN);
timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
val.it_value.tv_nsec = 1;
timer_settime(id, TIMER_ABSTIME, &val, NULL);
}
4) If the timer was initially armed with a former expiration value
before this call to timer_settime() and the current call sets an
early deadline that has already expired, the timer fires inline
within posix_cpu_timer_set(). In this case it must have been dequeued
before firing inline with its new expiration value, yet it hasn't
been disarmed in this case. So the process wide cputime counter and
the tick dependency may still be around for a while even after the
timer fired.
The following code snippet can reproduce this:
void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };
signal(SIGALRM, SIG_IGN);
timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
val.it_value.tv_sec = 100;
timer_settime(id, TIMER_ABSTIME, &val, NULL);
val.it_value.tv_sec = 0;
val.it_value.tv_nsec = 1;
timer_settime(id, TIMER_ABSTIME, &val, NULL);
}
Fix all these issues with triggering the related base next expiration
recalculation on the next tick. This also implies to re-evaluate the need
to keep around the process wide cputime counter and the tick dependency, in
a similar fashion to disarm_timer().
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-7-frederic@kernel.org
Remove the ad-hoc timer base accessors and provide a consolidated one.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-6-frederic@kernel.org
The end of the function cannot be reached with an error in variable
ret. Unconfuse reviewers about that.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-5-frederic@kernel.org
When an itimer deactivates a previously armed expiration, it simply doesn't
do anything. As a result the process wide cputime counter keeps running and
the tick dependency stays set until it reaches the old ghost expiration
value.
This can be reproduced with the following snippet:
void trigger_process_counter(void)
{
struct itimerval n = {};
n.it_value.tv_sec = 100;
setitimer(ITIMER_VIRTUAL, &n, NULL);
n.it_value.tv_sec = 0;
setitimer(ITIMER_VIRTUAL, &n, NULL);
}
Fix this with resetting the relevant base expiration. This is similar to
disarming a timer.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-4-frederic@kernel.org
A timer deletion only dequeues the timer but it doesn't shutdown
the related costly process wide cputimer counter and the tick dependency.
The following code snippet keeps this overhead around for one week after
the timer deletion:
void trigger_process_counter(void)
{
timer_t id;
struct itimerspec val = { };
val.it_value.tv_sec = 604800;
timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
timer_settime(id, 0, &val, NULL);
timer_delete(id);
}
Make sure the next target's tick recalculates the nearest expiration and
clears the process wide counter and tick dependency if necessary.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-3-frederic@kernel.org
Starting the process wide cputime counter needs to be done in the same
sighand locking sequence than actually arming the related timer otherwise
this races against concurrent timers setting/expiring in the same
threadgroup.
Detecting that the cputime counter is started without holding the sighand
lock is a first step toward debugging such situations.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-2-frederic@kernel.org
The variable ret is being initialized with a value that is never read, it
is being updated later on. The assignment is redundant and can be removed.
Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210721120147.109570-1-colin.king@canonical.com
The functions get_online_cpus() and put_online_cpus() have been
deprecated during the CPU hotplug rework. They map directly to
cpus_read_lock() and cpus_read_unlock().
Replace deprecated CPU-hotplug functions with the official version.
The behavior remains unchanged.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210803141621.780504-35-bigeasy@linutronix.de
syzbot reported KCSAN data races vs. timer_base::timer_running being set to
NULL without holding base::lock in expire_timers().
This looks innocent and most reads are clearly not problematic, but
Frederic identified an issue which is:
int data = 0;
void timer_func(struct timer_list *t)
{
data = 1;
}
CPU 0 CPU 1
------------------------------ --------------------------
base = lock_timer_base(timer, &flags); raw_spin_unlock(&base->lock);
if (base->running_timer != timer) call_timer_fn(timer, fn, baseclk);
ret = detach_if_pending(timer, base, true); base->running_timer = NULL;
raw_spin_unlock_irqrestore(&base->lock, flags); raw_spin_lock(&base->lock);
x = data;
If the timer has previously executed on CPU 1 and then CPU 0 can observe
base->running_timer == NULL and returns, assuming the timer has completed,
but it's not guaranteed on all architectures. The comment for
del_timer_sync() makes that guarantee. Moving the assignment under
base->lock prevents this.
For non-RT kernel it's performance wise completely irrelevant whether the
store happens before or after taking the lock. For an RT kernel moving the
store under the lock requires an extra unlock/lock pair in the case that
there is a waiter for the timer, but that's not the end of the world.
Reported-by: syzbot+aa7c2385d46c5eba0b89@syzkaller.appspotmail.com
Reported-by: syzbot+abea4558531bae1ba9fe@syzkaller.appspotmail.com
Fixes: 030dcdd197 ("timers: Prepare support for PREEMPT_RT")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/87lfea7gw8.fsf@nanos.tec.linutronix.de
Cc: stable@vger.kernel.org
31cd0e119d ("timers: Recalculate next timer interrupt only when
necessary") subtly altered get_next_timer_interrupt()'s behaviour. The
function no longer consistently returns KTIME_MAX with no timers
pending.
In order to decide if there are any timers pending we check whether the
next expiry will happen NEXT_TIMER_MAX_DELTA jiffies from now.
Unfortunately, the next expiry time and the timer base clock are no
longer updated in unison. The former changes upon certain timer
operations (enqueue, expire, detach), whereas the latter keeps track of
jiffies as they move forward. Ultimately breaking the logic above.
A simplified example:
- Upon entering get_next_timer_interrupt() with:
jiffies = 1
base->clk = 0;
base->next_expiry = NEXT_TIMER_MAX_DELTA;
'base->next_expiry == base->clk + NEXT_TIMER_MAX_DELTA', the function
returns KTIME_MAX.
- 'base->clk' is updated to the jiffies value.
- The next time we enter get_next_timer_interrupt(), taking into account
no timer operations happened:
base->clk = 1;
base->next_expiry = NEXT_TIMER_MAX_DELTA;
'base->next_expiry != base->clk + NEXT_TIMER_MAX_DELTA', the function
returns a valid expire time, which is incorrect.
This ultimately might unnecessarily rearm sched's timer on nohz_full
setups, and add latency to the system[1].
So, introduce 'base->timers_pending'[2], update it every time
'base->next_expiry' changes, and use it in get_next_timer_interrupt().
[1] See tick_nohz_stop_tick().
[2] A quick pahole check on x86_64 and arm64 shows it doesn't make
'struct timer_base' any bigger.
Fixes: 31cd0e119d ("timers: Recalculate next timer interrupt only when necessary")
Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Since the process wide cputime counter is started locklessly from
posix_cpu_timer_rearm(), it can be concurrently stopped by operations
on other timers from the same thread group, such as in the following
unlucky scenario:
CPU 0 CPU 1
----- -----
timer_settime(TIMER B)
posix_cpu_timer_rearm(TIMER A)
cpu_clock_sample_group()
(pct->timers_active already true)
handle_posix_cpu_timers()
check_process_timers()
stop_process_timers()
pct->timers_active = false
arm_timer(TIMER A)
tick -> run_posix_cpu_timers()
// sees !pct->timers_active, ignore
// our TIMER A
Fix this with simply locking process wide cputime counting start and
timer arm in the same block.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Fixes: 60f2ceaa81 ("posix-cpu-timers: Remove unnecessary locking around cpu_clock_sample_group")
Cc: stable@vger.kernel.org
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Pull RCU updates from Paul McKenney:
- Bitmap parsing support for "all" as an alias for all bits
- Documentation updates
- Miscellaneous fixes, including some that overlap into mm and lockdep
- kvfree_rcu() updates
- mem_dump_obj() updates, with acks from one of the slab-allocator
maintainers
- RCU NOCB CPU updates, including limited deoffloading
- SRCU updates
- Tasks-RCU updates
- Torture-test updates
* 'core-rcu-2021.07.04' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (78 commits)
tasks-rcu: Make show_rcu_tasks_gp_kthreads() be static inline
rcu-tasks: Make ksoftirqd provide RCU Tasks quiescent states
rcu: Add missing __releases() annotation
rcu: Remove obsolete rcu_read_unlock() deadlock commentary
rcu: Improve comments describing RCU read-side critical sections
rcu: Create an unrcu_pointer() to remove __rcu from a pointer
srcu: Early test SRCU polling start
rcu: Fix various typos in comments
rcu/nocb: Unify timers
rcu/nocb: Prepare for fine-grained deferred wakeup
rcu/nocb: Only cancel nocb timer if not polling
rcu/nocb: Delete bypass_timer upon nocb_gp wakeup
rcu/nocb: Cancel nocb_timer upon nocb_gp wakeup
rcu/nocb: Allow de-offloading rdp leader
rcu/nocb: Directly call __wake_nocb_gp() from bypass timer
rcu: Don't penalize priority boosting when there is nothing to boost
rcu: Point to documentation of ordering guarantees
rcu: Make rcu_gp_cleanup() be noinline for tracing
rcu: Restrict RCU_STRICT_GRACE_PERIOD to at most four CPUs
rcu: Make show_rcu_gp_kthreads() dump rcu_node structures blocking GP
...
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Merge tag 'timers-core-2021-06-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Time and clocksource/clockevent related updates:
Core changes:
- Infrastructure to support per CPU "broadcast" devices for per CPU
clockevent devices which stop in deep idle states. This allows us
to utilize the more efficient architected timer on certain ARM SoCs
for normal operation instead of permanentely using the slow to
access SoC specific clockevent device.
- Print the name of the broadcast/wakeup device in /proc/timer_list
- Make the clocksource watchdog more robust against delays between
reading the current active clocksource and the watchdog
clocksource. Such delays can be caused by NMIs, SMIs and vCPU
preemption.
Handle this by reading the watchdog clocksource twice, i.e. before
and after reading the current active clocksource. In case that the
two watchdog reads shows an excessive time delta, the read sequence
is repeated up to 3 times.
- Improve the debug output and add a test module for the watchdog
mechanism.
- Reimplementation of the venerable time64_to_tm() function with a
faster and significantly smaller version. Straight from the source,
i.e. the author of the related research paper contributed this!
Driver changes:
- No new drivers, not even new device tree bindings!
- Fixes, improvements and cleanups and all over the place"
* tag 'timers-core-2021-06-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (30 commits)
time/kunit: Add missing MODULE_LICENSE()
time: Improve performance of time64_to_tm()
clockevents: Use list_move() instead of list_del()/list_add()
clocksource: Print deviation in nanoseconds when a clocksource becomes unstable
clocksource: Provide kernel module to test clocksource watchdog
clocksource: Reduce clocksource-skew threshold
clocksource: Limit number of CPUs checked for clock synchronization
clocksource: Check per-CPU clock synchronization when marked unstable
clocksource: Retry clock read if long delays detected
clockevents: Add missing parameter documentation
clocksource/drivers/timer-ti-dm: Drop unnecessary restore
clocksource/arm_arch_timer: Improve Allwinner A64 timer workaround
clocksource/drivers/arm_global_timer: Remove duplicated argument in arm_global_timer
clocksource/drivers/arm_global_timer: Make symbol 'gt_clk_rate_change_nb' static
arm: zynq: don't disable CONFIG_ARM_GLOBAL_TIMER due to CONFIG_CPU_FREQ anymore
clocksource/drivers/arm_global_timer: Implement rate compensation whenever source clock changes
clocksource/drivers/ingenic: Rename unreasonable array names
clocksource/drivers/timer-ti-dm: Save and restore timer TIOCP_CFG
clocksource/drivers/mediatek: Ack and disable interrupts on suspend
clocksource/drivers/samsung_pwm: Constify source IO memory
...
- Micro-optimize tick_nohz_full_cpu()
- Optimize idle exit tick restarts to be less eager
- Optimize tick_nohz_dep_set_task() to only wake up
a single CPU. This reduces IPIs and interruptions
on nohz_full CPUs.
- Optimize tick_nohz_dep_set_signal() in a similar
fashion.
- Skip IPIs in tick_nohz_kick_task() when trying
to kick a non-running task.
- Micro-optimize tick_nohz_task_switch() IRQ flags
handling to reduce context switching costs.
- Misc cleanups and fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'timers-nohz-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timers/nohz updates from Ingo Molnar:
- Micro-optimize tick_nohz_full_cpu()
- Optimize idle exit tick restarts to be less eager
- Optimize tick_nohz_dep_set_task() to only wake up a single CPU.
This reduces IPIs and interruptions on nohz_full CPUs.
- Optimize tick_nohz_dep_set_signal() in a similar fashion.
- Skip IPIs in tick_nohz_kick_task() when trying to kick a
non-running task.
- Micro-optimize tick_nohz_task_switch() IRQ flags handling to
reduce context switching costs.
- Misc cleanups and fixes
* tag 'timers-nohz-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
MAINTAINERS: Add myself as context tracking maintainer
tick/nohz: Call tick_nohz_task_switch() with interrupts disabled
tick/nohz: Kick only _queued_ task whose tick dependency is updated
tick/nohz: Change signal tick dependency to wake up CPUs of member tasks
tick/nohz: Only wake up a single target cpu when kicking a task
tick/nohz: Update nohz_full Kconfig help
tick/nohz: Update idle_exittime on actual idle exit
tick/nohz: Remove superflous check for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
tick/nohz: Conditionally restart tick on idle exit
tick/nohz: Evaluate the CPU expression after the static key
The current implementation of time64_to_tm() contains unnecessary loops,
branches and look-up tables. The new one uses an arithmetic-based algorithm
appeared in [1] and is approximately 3x faster (YMMV).
The drawback is that the new code isn't intuitive and contains many 'magic
numbers' (not unusual for this type of algorithm). However, [1] justifies
all those numbers and, given this function's history, the code is unlikely
to need much maintenance, if any at all.
Add a KUnit test for it which checks every day in a 160,000 years interval
centered at 1970-01-01 against the expected result.
[1] Neri, Schneider, "Euclidean Affine Functions and Applications to
Calendar Algorithms". https://arxiv.org/abs/2102.06959
Signed-off-by: Cassio Neri <cassio.neri@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210622213616.313046-1-cassio.neri@gmail.com
Currently when an unstable clocksource is detected, the raw counters of
that clocksource and watchdog will be printed, which can only be understood
after some math calculation.
So print the delta in nanoseconds as well to make it easier for humans to
check the results.
[ paulmck: Fix typo. ]
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210527190124.440372-6-paulmck@kernel.org
When the clocksource watchdog marks a clock as unstable, this might
be due to that clock being unstable or it might be due to delays that
happen to occur between the reads of the two clocks. It would be good
to have a way of testing the clocksource watchdog's ability to
distinguish between these two causes of clock skew and instability.
Therefore, provide a new clocksource-wdtest module selected by a new
TEST_CLOCKSOURCE_WATCHDOG Kconfig option. This module has a single module
parameter named "holdoff" that provides the number of seconds of delay
before testing should start, which defaults to zero when built as a module
and to 10 seconds when built directly into the kernel. Very large systems
that boot slowly may need to increase the value of this module parameter.
This module uses hand-crafted clocksource structures to do its testing,
thus avoiding messing up timing for the rest of the kernel and for user
applications. This module first verifies that the ->uncertainty_margin
field of the clocksource structures are set sanely. It then tests the
delay-detection capability of the clocksource watchdog, increasing the
number of consecutive delays injected, first provoking console messages
complaining about the delays and finally forcing a clock-skew event.
Unexpected test results cause at least one WARN_ON_ONCE() console splat.
If there are no splats, the test has passed. Finally, it fuzzes the
value returned from a clocksource to test the clocksource watchdog's
ability to detect time skew.
This module checks the state of its clocksource after each test, and
uses WARN_ON_ONCE() to emit a console splat if there are any failures.
This should enable all types of test frameworks to detect any such
failures.
This facility is intended for diagnostic use only, and should be avoided
on production systems.
Reported-by: Chris Mason <clm@fb.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Feng Tang <feng.tang@intel.com>
Link: https://lore.kernel.org/r/20210527190124.440372-5-paulmck@kernel.org
Currently, WATCHDOG_THRESHOLD is set to detect a 62.5-millisecond skew in
a 500-millisecond WATCHDOG_INTERVAL. This requires that clocks be skewed
by more than 12.5% in order to be marked unstable. Except that a clock
that is skewed by that much is probably destroying unsuspecting software
right and left. And given that there are now checks for false-positive
skews due to delays between reading the two clocks, it should be possible
to greatly decrease WATCHDOG_THRESHOLD, at least for fine-grained clocks
such as TSC.
Therefore, add a new uncertainty_margin field to the clocksource structure
that contains the maximum uncertainty in nanoseconds for the corresponding
clock. This field may be initialized manually, as it is for
clocksource_tsc_early and clocksource_jiffies, which is copied to
refined_jiffies. If the field is not initialized manually, it will be
computed at clock-registry time as the period of the clock in question
based on the scale and freq parameters to __clocksource_update_freq_scale()
function. If either of those two parameters are zero, the
tens-of-milliseconds WATCHDOG_THRESHOLD is used as a cowardly alternative
to dividing by zero. No matter how the uncertainty_margin field is
calculated, it is bounded below by twice WATCHDOG_MAX_SKEW, that is, by 100
microseconds.
Note that manually initialized uncertainty_margin fields are not adjusted,
but there is a WARN_ON_ONCE() that triggers if any such field is less than
twice WATCHDOG_MAX_SKEW. This WARN_ON_ONCE() is intended to discourage
production use of the one-nanosecond uncertainty_margin values that are
used to test the clock-skew code itself.
The actual clock-skew check uses the sum of the uncertainty_margin fields
of the two clocksource structures being compared. Integer overflow is
avoided because the largest computed value of the uncertainty_margin
fields is one billion (10^9), and double that value fits into an
unsigned int. However, if someone manually specifies (say) UINT_MAX,
they will get what they deserve.
Note that the refined_jiffies uncertainty_margin field is initialized to
TICK_NSEC, which means that skew checks involving this clocksource will
be sufficently forgiving. In a similar vein, the clocksource_tsc_early
uncertainty_margin field is initialized to 32*NSEC_PER_MSEC, which
replicates the current behavior and allows custom setting if needed
in order to address the rare skews detected for this clocksource in
current mainline.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Feng Tang <feng.tang@intel.com>
Link: https://lore.kernel.org/r/20210527190124.440372-4-paulmck@kernel.org
Currently, if skew is detected on a clock marked CLOCK_SOURCE_VERIFY_PERCPU,
that clock is checked on all CPUs. This is thorough, but might not be
what you want on a system with a few tens of CPUs, let alone a few hundred
of them.
Therefore, by default check only up to eight randomly chosen CPUs. Also
provide a new clocksource.verify_n_cpus kernel boot parameter. A value of
-1 says to check all of the CPUs, and a non-negative value says to randomly
select that number of CPUs, without concern about selecting the same CPU
multiple times. However, make use of a cpumask so that a given CPU will be
checked at most once.
Suggested-by: Thomas Gleixner <tglx@linutronix.de> # For verify_n_cpus=1.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Feng Tang <feng.tang@intel.com>
Link: https://lore.kernel.org/r/20210527190124.440372-3-paulmck@kernel.org
Some sorts of per-CPU clock sources have a history of going out of
synchronization with each other. However, this problem has purportedy been
solved in the past ten years. Except that it is all too possible that the
problem has instead simply been made less likely, which might mean that
some of the occasional "Marking clocksource 'tsc' as unstable" messages
might be due to desynchronization. How would anyone know?
Therefore apply CPU-to-CPU synchronization checking to newly unstable
clocksource that are marked with the new CLOCK_SOURCE_VERIFY_PERCPU flag.
Lists of desynchronized CPUs are printed, with the caveat that if it
is the reporting CPU that is itself desynchronized, it will appear that
all the other clocks are wrong. Just like in real life.
Reported-by: Chris Mason <clm@fb.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Feng Tang <feng.tang@intel.com>
Link: https://lore.kernel.org/r/20210527190124.440372-2-paulmck@kernel.org
When the clocksource watchdog marks a clock as unstable, this might be due
to that clock being unstable or it might be due to delays that happen to
occur between the reads of the two clocks. Yes, interrupts are disabled
across those two reads, but there are no shortage of things that can delay
interrupts-disabled regions of code ranging from SMI handlers to vCPU
preemption. It would be good to have some indication as to why the clock
was marked unstable.
Therefore, re-read the watchdog clock on either side of the read from the
clock under test. If the watchdog clock shows an excessive time delta
between its pair of reads, the reads are retried.
The maximum number of retries is specified by a new kernel boot parameter
clocksource.max_cswd_read_retries, which defaults to three, that is, up to
four reads, one initial and up to three retries. If more than one retry
was required, a message is printed on the console (the occasional single
retry is expected behavior, especially in guest OSes). If the maximum
number of retries is exceeded, the clock under test will be marked
unstable. However, the probability of this happening due to various sorts
of delays is quite small. In addition, the reason (clock-read delays) for
the unstable marking will be apparent.
Reported-by: Chris Mason <clm@fb.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Feng Tang <feng.tang@intel.com>
Link: https://lore.kernel.org/r/20210527190124.440372-1-paulmck@kernel.org
There's an existing helper for setting TASK_RUNNING; must've gotten
lost last time we did this cleanup.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.409696194@infradead.org
With the introduction of per-cpu wakeup devices that can be used in
preference to the broadcast timer, print the name of such devices when
they are available.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210524221818.15850-6-will@kernel.org
When configuring the broadcast timer on entry to and exit from deep idle
states, prefer a per-CPU wakeup timer if one exists.
On entry to idle, stop the tick device and transfer the next event into
the oneshot wakeup device, which will serve as the wakeup from idle. To
avoid the overhead of additional hardware accesses on exit from idle,
leave the timer armed and treat the inevitable interrupt as a (possibly
spurious) tick event.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210524221818.15850-5-will@kernel.org
Some SoCs have two per-cpu timer implementations where the timer with the
higher rating stops in deep idle (i.e. suffers from CLOCK_EVT_FEAT_C3STOP)
but is otherwise preferable to the timer with the lower rating. In such a
design, selecting the higher rated devices relies on a global broadcast
timer and IPIs to wake up from deep idle states.
To avoid the reliance on a global broadcast timer and also to reduce the
overhead associated with the IPI wakeups, extend
tick_install_broadcast_device() to manage per-cpu wakeup timers separately
from the broadcast device.
For now, these timers remain unused.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210524221818.15850-4-will@kernel.org
In preparation for adding support for per-cpu wakeup timers, split
_tick_broadcast_oneshot_control() into a helper function which deals
only with the broadcast timer management across idle transitions.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210524221818.15850-3-will@kernel.org
tick-broadcast.o is only built if CONFIG_GENERIC_CLOCKEVENTS_BROADCAST=y
so remove the redundant #ifdef guards around the definition of
tick_receive_broadcast().
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210524221818.15850-2-will@kernel.org
Use the DEVICE_ATTR_[RO|WO] helpers instead of plain DEVICE_ATTR, which
makes the code a bit shorter and easier to read.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210523065825.19684-1-yuehaibing@huawei.com
Checking for and processing RCU-nocb deferred wakeup upon user/guest
entry is only relevant when nohz_full runs on the local CPU, otherwise
the periodic tick should take care of it.
Make sure we don't needlessly pollute these fast-paths as a -3%
performance regression on a will-it-scale.per_process_ops has been
reported so far.
Fixes: 47b8ff194c (entry: Explicitly flush pending rcuog wakeup before last rescheduling point)
Fixes: 4ae7dc97f7 (entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point)
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210527113441.465489-1-frederic@kernel.org
Call tick_nohz_task_switch() slightly earlier after the context switch
to benefit from disabled IRQs. This way the function doesn't need to
disable them once more.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210512232924.150322-10-frederic@kernel.org
When the tick dependency of a task is updated, we want it to aknowledge
the new state and restart the tick if needed. If the task is not
running, we don't need to kick it because it will observe the new
dependency upon scheduling in. But if the task is running, we may need
to send an IPI to it so that it gets notified.
Unfortunately we don't have the means to check if a task is running
in a race free way. Checking p->on_cpu in a synchronized way against
p->tick_dep_mask would imply adding a full barrier between
prepare_task_switch() and tick_nohz_task_switch(), which we want to
avoid in this fast-path.
Therefore we blindly fire an IPI to the task's CPU.
Meanwhile we can check if the task is queued on the CPU rq because
p->on_rq is always set to TASK_ON_RQ_QUEUED _before_ schedule() and its
full barrier that precedes tick_nohz_task_switch(). And if the task is
queued on a nohz_full CPU, it also has fair chances to be running as the
isolation constraints prescribe running single tasks on full dynticks
CPUs.
So use this as a trick to check if we can spare an IPI toward a
non-running task.
NOTE: For the ordering to be correct, it is assumed that we never
deactivate a task while it is running, the only exception being the task
deactivating itself while scheduling out.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-9-frederic@kernel.org
Rather than waking up all nohz_full CPUs on the system, only wake up
the target CPUs of member threads of the signal.
Reduces interruptions to nohz_full CPUs.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-8-frederic@kernel.org
When adding a tick dependency to a task, its necessary to
wake up the CPU where the task resides to reevaluate tick
dependencies on that CPU.
However the current code wakes up all nohz_full CPUs, which
is unnecessary.
Switch to waking up a single CPU, by using ordering of writes
to task->cpu and task->tick_dep_mask.
[ mingo: Minor readability edit. ]
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-7-frederic@kernel.org
CONFIG_NO_HZ_FULL behaves just like CONFIG_NO_HZ_IDLE by default.
Reassure distros about it.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-6-frederic@kernel.org
The idle_exittime field of tick_sched is used to record the time when
the idle state was left. but currently the idle_exittime is updated in
the function tick_nohz_restart_sched_tick(), which is not always in idle
state when nohz_full is configured:
tick_irq_exit
tick_nohz_irq_exit
tick_nohz_full_update_tick
tick_nohz_restart_sched_tick
ts->idle_exittime = now;
It's thus overwritten by mistake on nohz_full tick restart. Move the
update to the appropriate idle exit path instead.
Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-5-frederic@kernel.org
The vtime_accounting_enabled_this_cpu() early check already makes what
follows as dead code in the case of CONFIG_VIRT_CPU_ACCOUNTING_NATIVE.
No need to keep the ifdeferry around.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-4-frederic@kernel.org
In nohz_full mode, switching from idle to a task will unconditionally
issue a tick restart. If the task is alone in the runqueue or is the
highest priority, the tick will fire once then eventually stop. But that
alone is still undesired noise.
Therefore, only restart the tick on idle exit when it's strictly
necessary.
Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-3-frederic@kernel.org
RTC drivers used to leave .set_alarm() NULL in order to signal the RTC
device doesn't support alarms. The drivers are now clearing the
RTC_FEATURE_ALARM bit for that purpose in order to keep the rtc_class_ops
structure const. So now, .set_alarm() is set unconditionally and this
possibly causes the alarmtimer code to select an RTC device that doesn't
support alarms.
Test RTC_FEATURE_ALARM instead of relying on ops->set_alarm to determine
whether alarms are available.
Fixes: 7ae41220ef ("rtc: introduce features bitfield")
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210511014516.563031-1-alexandre.belloni@bootlin.com
This reverts commit dcd42591eb.
The only user was RCU/nocb.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
- Stage-2 isolation for the host kernel when running in protected mode
- Guest SVE support when running in nVHE mode
- Force W^X hypervisor mappings in nVHE mode
- ITS save/restore for guests using direct injection with GICv4.1
- nVHE panics now produce readable backtraces
- Guest support for PTP using the ptp_kvm driver
- Performance improvements in the S2 fault handler
x86:
- Optimizations and cleanup of nested SVM code
- AMD: Support for virtual SPEC_CTRL
- Optimizations of the new MMU code: fast invalidation,
zap under read lock, enable/disably dirty page logging under
read lock
- /dev/kvm API for AMD SEV live migration (guest API coming soon)
- support SEV virtual machines sharing the same encryption context
- support SGX in virtual machines
- add a few more statistics
- improved directed yield heuristics
- Lots and lots of cleanups
Generic:
- Rework of MMU notifier interface, simplifying and optimizing
the architecture-specific code
- Some selftests improvements
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm updates from Paolo Bonzini:
"This is a large update by KVM standards, including AMD PSP (Platform
Security Processor, aka "AMD Secure Technology") and ARM CoreSight
(debug and trace) changes.
ARM:
- CoreSight: Add support for ETE and TRBE
- Stage-2 isolation for the host kernel when running in protected
mode
- Guest SVE support when running in nVHE mode
- Force W^X hypervisor mappings in nVHE mode
- ITS save/restore for guests using direct injection with GICv4.1
- nVHE panics now produce readable backtraces
- Guest support for PTP using the ptp_kvm driver
- Performance improvements in the S2 fault handler
x86:
- AMD PSP driver changes
- Optimizations and cleanup of nested SVM code
- AMD: Support for virtual SPEC_CTRL
- Optimizations of the new MMU code: fast invalidation, zap under
read lock, enable/disably dirty page logging under read lock
- /dev/kvm API for AMD SEV live migration (guest API coming soon)
- support SEV virtual machines sharing the same encryption context
- support SGX in virtual machines
- add a few more statistics
- improved directed yield heuristics
- Lots and lots of cleanups
Generic:
- Rework of MMU notifier interface, simplifying and optimizing the
architecture-specific code
- a handful of "Get rid of oprofile leftovers" patches
- Some selftests improvements"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (379 commits)
KVM: selftests: Speed up set_memory_region_test
selftests: kvm: Fix the check of return value
KVM: x86: Take advantage of kvm_arch_dy_has_pending_interrupt()
KVM: SVM: Skip SEV cache flush if no ASIDs have been used
KVM: SVM: Remove an unnecessary prototype declaration of sev_flush_asids()
KVM: SVM: Drop redundant svm_sev_enabled() helper
KVM: SVM: Move SEV VMCB tracking allocation to sev.c
KVM: SVM: Explicitly check max SEV ASID during sev_hardware_setup()
KVM: SVM: Unconditionally invoke sev_hardware_teardown()
KVM: SVM: Enable SEV/SEV-ES functionality by default (when supported)
KVM: SVM: Condition sev_enabled and sev_es_enabled on CONFIG_KVM_AMD_SEV=y
KVM: SVM: Append "_enabled" to module-scoped SEV/SEV-ES control variables
KVM: SEV: Mask CPUID[0x8000001F].eax according to supported features
KVM: SVM: Move SEV module params/variables to sev.c
KVM: SVM: Disable SEV/SEV-ES if NPT is disabled
KVM: SVM: Free sev_asid_bitmap during init if SEV setup fails
KVM: SVM: Zero out the VMCB array used to track SEV ASID association
x86/sev: Drop redundant and potentially misleading 'sev_enabled'
KVM: x86: Move reverse CPUID helpers to separate header file
KVM: x86: Rename GPR accessors to make mode-aware variants the defaults
...
- Add idle states table for IceLake-D to the intel_idle driver and
update IceLake-X C6 data in it (Artem Bityutskiy).
- Fix the C7 idle state on Tegra114 in the tegra cpuidle driver and
drop the unused do_idle() firmware call from it (Dmitry Osipenko).
- Fix cpuidle-qcom-spm Kconfig entry (He Ying).
- Fix handling of possible negative tick_nohz_get_next_hrtimer()
return values of in cpuidle governors (Rafael Wysocki).
- Add support for frequency-invariance to the ACPI CPPC cpufreq
driver and update the frequency-invariance engine (FIE) to use it
as needed (Viresh Kumar).
- Simplify the default delay_us setting in the ACPI CPPC cpufreq
driver (Tom Saeger).
- Clean up frequency-related computations in the intel_pstate
cpufreq driver (Rafael Wysocki).
- Fix TBG parent setting for load levels in the armada-37xx
cpufreq driver and drop the CPU PM clock .set_parent method for
armada-37xx (Marek Behún).
- Fix multiple issues in the armada-37xx cpufreq driver (Pali Rohár).
- Fix handling of dev_pm_opp_of_cpumask_add_table() return values
in cpufreq-dt to take the -EPROBE_DEFER one into acconut as
appropriate (Quanyang Wang).
- Fix format string in ia64-acpi-cpufreq (Sergei Trofimovich).
- Drop the unused for_each_policy() macro from cpufreq (Shaokun
Zhang).
- Simplify computations in the schedutil cpufreq governor to avoid
unnecessary overhead (Yue Hu).
- Fix typos in the s5pv210 cpufreq driver (Bhaskar Chowdhury).
- Fix cpufreq documentation links in Kconfig (Alexander Monakov).
- Fix PCI device power state handling in pci_enable_device_flags()
to avoid issuse in some cases when the device depends on an ACPI
power resource (Rafael Wysocki).
- Add missing documentation of pm_runtime_resume_and_get() (Alan
Stern).
- Add missing static inline stub for pm_runtime_has_no_callbacks()
to pm_runtime.h and drop the unused try_to_freeze_nowarn()
definition (YueHaibing).
- Drop duplicate struct device declaration from pm.h and fix a
structure type declaration in intel_rapl.h (Wan Jiabing).
- Use dev_set_name() instead of an open-coded equivalent of it in
the wakeup sources code and drop a redundant local variable
initialization from it (Andy Shevchenko, Colin Ian King).
- Use crc32 instead of md5 for e820 memory map integrity check
during resume from hibernation on x86 (Chris von Recklinghausen).
- Fix typos in comments in the system-wide and hibernation support
code (Lu Jialin).
- Modify the generic power domains (genpd) code to avoid resuming
devices in the "prepare" phase of system-wide suspend and
hibernation (Ulf Hansson).
- Add Hygon Fam18h RAPL support to the intel_rapl power capping
driver (Pu Wen).
- Add MAINTAINERS entry for the dynamic thermal power management
(DTPM) code (Daniel Lezcano).
- Add devm variants of operating performance points (OPP) API
functions and switch over some users of the OPP framework to
the new resource-managed API (Yangtao Li and Dmitry Osipenko).
- Update devfreq core:
* Register devfreq devices as cooling devices on demand (Daniel
Lezcano).
* Add missing unlock opeation in devfreq_add_device() (Lukasz
Luba).
* Use the next frequency as resume_freq instead of the previous
frequency when using the opp-suspend property (Dong Aisheng).
* Check get_dev_status in devfreq_update_stats() (Dong Aisheng).
* Fix set_freq path for the userspace governor in Kconfig (Dong
Aisheng).
* Remove invalid description of get_target_freq() (Dong Aisheng).
- Update devfreq drivers:
* imx8m-ddrc: Remove imx8m_ddrc_get_dev_status() and unneeded
of_match_ptr() (Dong Aisheng, Fabio Estevam).
* rk3399_dmc: dt-bindings: Add rockchip,pmu phandle and drop
references to undefined symbols (Enric Balletbo i Serra, Gaël
PORTAY).
* rk3399_dmc: Use dev_err_probe() to simplify the code (Krzysztof
Kozlowski).
* imx-bus: Remove unneeded of_match_ptr() (Fabio Estevam).
- Fix kernel-doc warnings in three places (Pierre-Louis Bossart).
- Fix typo in the pm-graph utility code (Ricardo Ribalda).
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Merge tag 'pm-5.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull power management updates from Rafael Wysocki:
"These add some new hardware support (for example, IceLake-D idle
states in intel_idle), fix some issues (for example, the handling of
negative "sleep length" values in cpuidle governors), add new
functionality to the existing drivers (for example, scale-invariance
support in the ACPI CPPC cpufreq driver) and clean up code all over.
Specifics:
- Add idle states table for IceLake-D to the intel_idle driver and
update IceLake-X C6 data in it (Artem Bityutskiy).
- Fix the C7 idle state on Tegra114 in the tegra cpuidle driver and
drop the unused do_idle() firmware call from it (Dmitry Osipenko).
- Fix cpuidle-qcom-spm Kconfig entry (He Ying).
- Fix handling of possible negative tick_nohz_get_next_hrtimer()
return values of in cpuidle governors (Rafael Wysocki).
- Add support for frequency-invariance to the ACPI CPPC cpufreq
driver and update the frequency-invariance engine (FIE) to use it
as needed (Viresh Kumar).
- Simplify the default delay_us setting in the ACPI CPPC cpufreq
driver (Tom Saeger).
- Clean up frequency-related computations in the intel_pstate cpufreq
driver (Rafael Wysocki).
- Fix TBG parent setting for load levels in the armada-37xx cpufreq
driver and drop the CPU PM clock .set_parent method for armada-37xx
(Marek Behún).
- Fix multiple issues in the armada-37xx cpufreq driver (Pali Rohár).
- Fix handling of dev_pm_opp_of_cpumask_add_table() return values in
cpufreq-dt to take the -EPROBE_DEFER one into acconut as
appropriate (Quanyang Wang).
- Fix format string in ia64-acpi-cpufreq (Sergei Trofimovich).
- Drop the unused for_each_policy() macro from cpufreq (Shaokun
Zhang).
- Simplify computations in the schedutil cpufreq governor to avoid
unnecessary overhead (Yue Hu).
- Fix typos in the s5pv210 cpufreq driver (Bhaskar Chowdhury).
- Fix cpufreq documentation links in Kconfig (Alexander Monakov).
- Fix PCI device power state handling in pci_enable_device_flags() to
avoid issuse in some cases when the device depends on an ACPI power
resource (Rafael Wysocki).
- Add missing documentation of pm_runtime_resume_and_get() (Alan
Stern).
- Add missing static inline stub for pm_runtime_has_no_callbacks() to
pm_runtime.h and drop the unused try_to_freeze_nowarn() definition
(YueHaibing).
- Drop duplicate struct device declaration from pm.h and fix a
structure type declaration in intel_rapl.h (Wan Jiabing).
- Use dev_set_name() instead of an open-coded equivalent of it in the
wakeup sources code and drop a redundant local variable
initialization from it (Andy Shevchenko, Colin Ian King).
- Use crc32 instead of md5 for e820 memory map integrity check during
resume from hibernation on x86 (Chris von Recklinghausen).
- Fix typos in comments in the system-wide and hibernation support
code (Lu Jialin).
- Modify the generic power domains (genpd) code to avoid resuming
devices in the "prepare" phase of system-wide suspend and
hibernation (Ulf Hansson).
- Add Hygon Fam18h RAPL support to the intel_rapl power capping
driver (Pu Wen).
- Add MAINTAINERS entry for the dynamic thermal power management
(DTPM) code (Daniel Lezcano).
- Add devm variants of operating performance points (OPP) API
functions and switch over some users of the OPP framework to the
new resource-managed API (Yangtao Li and Dmitry Osipenko).
- Update devfreq core:
* Register devfreq devices as cooling devices on demand (Daniel
Lezcano).
* Add missing unlock opeation in devfreq_add_device() (Lukasz
Luba).
* Use the next frequency as resume_freq instead of the previous
frequency when using the opp-suspend property (Dong Aisheng).
* Check get_dev_status in devfreq_update_stats() (Dong Aisheng).
* Fix set_freq path for the userspace governor in Kconfig (Dong
Aisheng).
* Remove invalid description of get_target_freq() (Dong Aisheng).
- Update devfreq drivers:
* imx8m-ddrc: Remove imx8m_ddrc_get_dev_status() and unneeded
of_match_ptr() (Dong Aisheng, Fabio Estevam).
* rk3399_dmc: dt-bindings: Add rockchip,pmu phandle and drop
references to undefined symbols (Enric Balletbo i Serra, Gaël
PORTAY).
* rk3399_dmc: Use dev_err_probe() to simplify the code (Krzysztof
Kozlowski).
* imx-bus: Remove unneeded of_match_ptr() (Fabio Estevam).
- Fix kernel-doc warnings in three places (Pierre-Louis Bossart).
- Fix typo in the pm-graph utility code (Ricardo Ribalda)"
* tag 'pm-5.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (74 commits)
PM: wakeup: remove redundant assignment to variable retval
PM: hibernate: x86: Use crc32 instead of md5 for hibernation e820 integrity check
cpufreq: Kconfig: fix documentation links
PM: wakeup: use dev_set_name() directly
PM: runtime: Add documentation for pm_runtime_resume_and_get()
cpufreq: intel_pstate: Simplify intel_pstate_update_perf_limits()
cpufreq: armada-37xx: Fix module unloading
cpufreq: armada-37xx: Remove cur_frequency variable
cpufreq: armada-37xx: Fix determining base CPU frequency
cpufreq: armada-37xx: Fix driver cleanup when registration failed
clk: mvebu: armada-37xx-periph: Fix workaround for switching from L1 to L0
clk: mvebu: armada-37xx-periph: Fix switching CPU freq from 250 Mhz to 1 GHz
cpufreq: armada-37xx: Fix the AVS value for load L1
clk: mvebu: armada-37xx-periph: remove .set_parent method for CPU PM clock
cpufreq: armada-37xx: Fix setting TBG parent for load levels
cpuidle: Fix ARM_QCOM_SPM_CPUIDLE configuration
cpuidle: tegra: Remove do_idle firmware call
cpuidle: tegra: Fix C7 idling state on Tegra114
PM: sleep: fix typos in comments
cpufreq: Remove unused for_each_policy macro
...
Core changes:
- Allow runtime power management when the clocksource is changed.
- A correctness fix for clock_adjtime32() so that the return value
on success is not overwritten by the result of the copy to user.
- Allow late installment of broadcast clockevent devices which was
broken because nothing switched them over to oneshot mode. This went
unnoticed so far because clockevent devices used to be built in, but
now people started to make them modular.
- Debugfs related simplifications
- Small cleanups and improvements here and there
Driver changes:
- The usual set of device tree binding updates for a wide range
of drivers/devices.
- The usual updates and improvements for drivers all over the place but
nothing outstanding.
- No new clocksource/event drivers. They'll come back next time.
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Merge tag 'timers-core-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"The time and timers updates contain:
Core changes:
- Allow runtime power management when the clocksource is changed.
- A correctness fix for clock_adjtime32() so that the return value on
success is not overwritten by the result of the copy to user.
- Allow late installment of broadcast clockevent devices which was
broken because nothing switched them over to oneshot mode. This
went unnoticed so far because clockevent devices used to be built
in, but now people started to make them modular.
- Debugfs related simplifications
- Small cleanups and improvements here and there
Driver changes:
- The usual set of device tree binding updates for a wide range of
drivers/devices.
- The usual updates and improvements for drivers all over the place
but nothing outstanding.
- No new clocksource/event drivers. They'll come back next time"
* tag 'timers-core-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
posix-timers: Preserve return value in clock_adjtime32()
tick/broadcast: Allow late registered device to enter oneshot mode
tick: Use tick_check_replacement() instead of open coding it
time/timecounter: Mark 1st argument of timecounter_cyc2time() as const
dt-bindings: timer: nuvoton,npcm7xx: Add wpcm450-timer
clocksource/drivers/arm_arch_timer: Add __ro_after_init and __init
clocksource/drivers/timer-ti-dm: Handle dra7 timer wrap errata i940
clocksource/drivers/timer-ti-dm: Prepare to handle dra7 timer wrap issue
clocksource/drivers/dw_apb_timer_of: Add handling for potential memory leak
clocksource/drivers/npcm: Add support for WPCM450
clocksource/drivers/sh_cmt: Don't use CMTOUT_IE with R-Car Gen2/3
clocksource/drivers/pistachio: Fix trivial typo
clocksource/drivers/ingenic_ost: Fix return value check in ingenic_ost_probe()
clocksource/drivers/timer-ti-dm: Add missing set_state_oneshot_stopped
clocksource/drivers/timer-ti-dm: Fix posted mode status check order
dt-bindings: timer: renesas,cmt: Document R8A77961
dt-bindings: timer: renesas,cmt: Add r8a779a0 CMT support
clocksource/drivers/ingenic-ost: Add support for the JZ4760B
clocksource/drivers/ingenic: Add support for the JZ4760
dt-bindings: timer: ingenic: Add compatible strings for JZ4760(B)
...
Core changes:
- Provide IRQF_NO_AUTOEN as a flag for request*_irq() so drivers can be
cleaned up which either use a seperate mechanism to prevent auto-enable
at request time or have a racy mechanism which disables the interrupt
right after request.
- Get rid of the last usage of irq_create_identity_mapping() and remove
the interface.
- An overhaul of tasklet_disable(). Most usage sites of tasklet_disable()
are in task context and usually in cleanup, teardown code pathes.
tasklet_disable() spinwaits for a tasklet which is currently executed.
That's not only a problem for PREEMPT_RT where this can lead to a live
lock when the disabling task preempts the softirq thread. It's also
problematic in context of virtualization when the vCPU which runs the
tasklet is scheduled out and the disabling code has to spin wait until
it's scheduled back in. Though there are a few code pathes which invoke
tasklet_disable() from non-sleepable context. For these a new disable
variant which still spinwaits is provided which allows to switch
tasklet_disable() to a sleep wait mechanism. For the atomic use cases
this does not solve the live lock issue on PREEMPT_RT. That is mitigated
by blocking on the RT specific softirq lock.
- The PREEMPT_RT specific implementation of softirq processing and
local_bh_disable/enable().
On RT enabled kernels soft interrupt processing happens always in task
context and all interrupt handlers, which are not explicitly marked to
be invoked in hard interrupt context are forced into task context as
well. This allows to protect against softirq processing with a per
CPU lock, which in turn allows to make BH disabled regions preemptible.
Most of the softirq handling code is still shared. The RT/non-RT
specific differences are addressed with a set of inline functions which
provide the context specific functionality. The local_bh_disable() /
local_bh_enable() mechanism are obviously seperate.
- The usual set of small improvements and cleanups
Driver changes:
- New drivers for Nuvoton WPCM450 and DT 79rc3243x interrupt controllers
- Extended functionality for MStar, STM32 and SC7280 irq chips
- Enhanced robustness for ARM GICv3/4.1 drivers
- The usual set of cleanups and improvements all over the place
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Merge tag 'irq-core-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq updates from Thomas Gleixner:
"The usual updates from the irq departement:
Core changes:
- Provide IRQF_NO_AUTOEN as a flag for request*_irq() so drivers can
be cleaned up which either use a seperate mechanism to prevent
auto-enable at request time or have a racy mechanism which disables
the interrupt right after request.
- Get rid of the last usage of irq_create_identity_mapping() and
remove the interface.
- An overhaul of tasklet_disable().
Most usage sites of tasklet_disable() are in task context and
usually in cleanup, teardown code pathes. tasklet_disable()
spinwaits for a tasklet which is currently executed. That's not
only a problem for PREEMPT_RT where this can lead to a live lock
when the disabling task preempts the softirq thread. It's also
problematic in context of virtualization when the vCPU which runs
the tasklet is scheduled out and the disabling code has to spin
wait until it's scheduled back in.
There are a few code pathes which invoke tasklet_disable() from
non-sleepable context. For these a new disable variant which still
spinwaits is provided which allows to switch tasklet_disable() to a
sleep wait mechanism. For the atomic use cases this does not solve
the live lock issue on PREEMPT_RT. That is mitigated by blocking on
the RT specific softirq lock.
- The PREEMPT_RT specific implementation of softirq processing and
local_bh_disable/enable().
On RT enabled kernels soft interrupt processing happens always in
task context and all interrupt handlers, which are not explicitly
marked to be invoked in hard interrupt context are forced into task
context as well. This allows to protect against softirq processing
with a per CPU lock, which in turn allows to make BH disabled
regions preemptible.
Most of the softirq handling code is still shared. The RT/non-RT
specific differences are addressed with a set of inline functions
which provide the context specific functionality. The
local_bh_disable() / local_bh_enable() mechanism are obviously
seperate.
- The usual set of small improvements and cleanups
Driver changes:
- New drivers for Nuvoton WPCM450 and DT 79rc3243x interrupt
controllers
- Extended functionality for MStar, STM32 and SC7280 irq chips
- Enhanced robustness for ARM GICv3/4.1 drivers
- The usual set of cleanups and improvements all over the place"
* tag 'irq-core-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (53 commits)
irqchip/xilinx: Expose Kconfig option for Zynq/ZynqMP
irqchip/gic-v3: Do not enable irqs when handling spurious interrups
dt-bindings: interrupt-controller: Add IDT 79RC3243x Interrupt Controller
irqchip: Add support for IDT 79rc3243x interrupt controller
irqdomain: Drop references to recusive irqdomain setup
irqdomain: Get rid of irq_create_strict_mappings()
irqchip/jcore-aic: Kill use of irq_create_strict_mappings()
ARM: PXA: Kill use of irq_create_strict_mappings()
irqchip/gic-v4.1: Disable vSGI upon (GIC CPUIF < v4.1) detection
irqchip/tb10x: Use 'fallthrough' to eliminate a warning
genirq: Reduce irqdebug cacheline bouncing
kernel: Initialize cpumask before parsing
irqchip/wpcm450: Drop COMPILE_TEST
irqchip/irq-mst: Support polarity configuration
irqchip: Add driver for WPCM450 interrupt controller
dt-bindings: interrupt-controller: Add nuvoton, wpcm450-aic
dt-bindings: qcom,pdc: Add compatible for sc7280
irqchip/stm32: Add usart instances exti direct event support
irqchip/gic-v3: Fix OF_BAD_ADDR error handling
irqchip/sifive-plic: Mark two global variables __ro_after_init
...
New features:
- Stage-2 isolation for the host kernel when running in protected mode
- Guest SVE support when running in nVHE mode
- Force W^X hypervisor mappings in nVHE mode
- ITS save/restore for guests using direct injection with GICv4.1
- nVHE panics now produce readable backtraces
- Guest support for PTP using the ptp_kvm driver
- Performance improvements in the S2 fault handler
- Alexandru is now a reviewer (not really a new feature...)
Fixes:
- Proper emulation of the GICR_TYPER register
- Handle the complete set of relocation in the nVHE EL2 object
- Get rid of the oprofile dependency in the PMU code (and of the
oprofile body parts at the same time)
- Debug and SPE fixes
- Fix vcpu reset
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Merge tag 'kvmarm-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD
KVM/arm64 updates for Linux 5.13
New features:
- Stage-2 isolation for the host kernel when running in protected mode
- Guest SVE support when running in nVHE mode
- Force W^X hypervisor mappings in nVHE mode
- ITS save/restore for guests using direct injection with GICv4.1
- nVHE panics now produce readable backtraces
- Guest support for PTP using the ptp_kvm driver
- Performance improvements in the S2 fault handler
- Alexandru is now a reviewer (not really a new feature...)
Fixes:
- Proper emulation of the GICR_TYPER register
- Handle the complete set of relocation in the nVHE EL2 object
- Get rid of the oprofile dependency in the PMU code (and of the
oprofile body parts at the same time)
- Debug and SPE fixes
- Fix vcpu reset
The return value on success (>= 0) is overwritten by the return value of
put_old_timex32(). That works correct in the fault case, but is wrong for
the success case where put_old_timex32() returns 0.
Just check the return value of put_old_timex32() and return -EFAULT in case
it is not zero.
[ tglx: Massage changelog ]
Fixes: 3a4d44b616 ("ntp: Move adjtimex related compat syscalls to native counterparts")
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Richard Cochran <richardcochran@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210414030449.90692-1-chenjun102@huawei.com
The broadcast device is switched to oneshot mode when the system switches
to oneshot mode. If a broadcast clock event device is registered after the
system switched to oneshot mode, it will stay in periodic mode forever.
Ensure that a late registered device which is selected as broadcast device
is initialized in oneshot mode when the system already uses oneshot mode.
[ tglx: Massage changelog ]
Signed-off-by: Jindong Yue <jindong.yue@nxp.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210331083318.21794-1-jindong.yue@nxp.com
The function tick_check_replacement() is the combination of
tick_check_percpu() and tick_check_preferred(), but tick_check_new_device()
has the same logic open coded.
Use the helper to simplify the code.
[ tglx: Massage changelog ]
Signed-off-by: Wang Wensheng <wangwensheng4@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210326022328.3266-1-wangwensheng4@huawei.com
Make the tick_nohz_get_next_hrtimer() kerneldoc comment state clearly
that the function may return negative numbers.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
System time snapshots are not conveying information about the current
clocksource which was used, but callers like the PTP KVM guest
implementation have the requirement to evaluate the clocksource type to
select the appropriate mechanism.
Introduce a clocksource id field in struct clocksource which is by default
set to CSID_GENERIC (0). Clocksource implementations can set that field to
a value which allows to identify the clocksource.
Store the clocksource id of the current clocksource in the
system_time_snapshot so callers can evaluate which clocksource was used to
take the snapshot and act accordingly.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201209060932.212364-5-jianyong.wu@arm.com
The struct clocksource callbacks enable() and disable() are described as a
way to allow clock sources to enter a power save mode. See commit
4614e6adaf ("clocksource: add enable() and disable() callbacks")
But using runtime PM from these callbacks triggers a cyclic lockdep warning when
switching clock source using change_clocksource().
# echo e60f0000.timer > /sys/devices/system/clocksource/clocksource0/current_clocksource
======================================================
WARNING: possible circular locking dependency detected
------------------------------------------------------
migration/0/11 is trying to acquire lock:
ffff0000403ed220 (&dev->power.lock){-...}-{2:2}, at: __pm_runtime_resume+0x40/0x74
but task is already holding lock:
ffff8000113c8f88 (tk_core.seq.seqcount){----}-{0:0}, at: multi_cpu_stop+0xa4/0x190
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (tk_core.seq.seqcount){----}-{0:0}:
ktime_get+0x28/0xa0
hrtimer_start_range_ns+0x210/0x2dc
generic_sched_clock_init+0x70/0x88
sched_clock_init+0x40/0x64
start_kernel+0x494/0x524
-> #1 (hrtimer_bases.lock){-.-.}-{2:2}:
hrtimer_start_range_ns+0x68/0x2dc
rpm_suspend+0x308/0x5dc
rpm_idle+0xc4/0x2a4
pm_runtime_work+0x98/0xc0
process_one_work+0x294/0x6f0
worker_thread+0x70/0x45c
kthread+0x154/0x160
ret_from_fork+0x10/0x20
-> #0 (&dev->power.lock){-...}-{2:2}:
_raw_spin_lock_irqsave+0x7c/0xc4
__pm_runtime_resume+0x40/0x74
sh_cmt_start+0x1c4/0x260
sh_cmt_clocksource_enable+0x28/0x50
change_clocksource+0x9c/0x160
multi_cpu_stop+0xa4/0x190
cpu_stopper_thread+0x90/0x154
smpboot_thread_fn+0x244/0x270
kthread+0x154/0x160
ret_from_fork+0x10/0x20
other info that might help us debug this:
Chain exists of:
&dev->power.lock --> hrtimer_bases.lock --> tk_core.seq.seqcount
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(tk_core.seq.seqcount);
lock(hrtimer_bases.lock);
lock(tk_core.seq.seqcount);
lock(&dev->power.lock);
*** DEADLOCK ***
2 locks held by migration/0/11:
#0: ffff8000113c9278 (timekeeper_lock){-.-.}-{2:2}, at: change_clocksource+0x2c/0x160
#1: ffff8000113c8f88 (tk_core.seq.seqcount){----}-{0:0}, at: multi_cpu_stop+0xa4/0x190
Rework change_clocksource() so it enables the new clocksource and disables
the old clocksource outside of the timekeeper_lock and seqcount write held
region. There is no requirement that these callbacks are invoked from the
lock held region.
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20210211134318.323910-1-niklas.soderlund+renesas@ragnatech.se
There is no need to keep the dentry pointer around for the created
debugfs file, as it is only needed when removing it from the system.
When it is to be removed, ask debugfs itself for the pointer, to save on
storage and make things a bit simpler.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210216155020.1012407-1-gregkh@linuxfoundation.org
On RT a task which has soft interrupts disabled can block on a lock and
schedule out to idle while soft interrupts are pending. This triggers the
warning in the NOHZ idle code which complains about going idle with pending
soft interrupts. But as the task is blocked soft interrupt processing is
temporarily blocked as well which means that such a warning is a false
positive.
To prevent that check the per CPU state which indicates that a scheduled
out task has soft interrupts disabled.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210309085727.527563866@linutronix.de
Preparation for fixing get_nr_restart_syscall() on X86 for COMPAT.
Add a new helper which sets restart_block->fn and calls a dummy
arch_set_restart_data() helper.
Fixes: 609c19a385 ("x86/ptrace: Stop setting TS_COMPAT in ptrace code")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210201174641.GA17871@redhat.com
hrtimer_force_reprogram() and hrtimer_interrupt() invokes
__hrtimer_get_next_event() to find the earliest expiry time of hrtimer
bases. __hrtimer_get_next_event() does not update
cpu_base::[softirq_]_expires_next to preserve reprogramming logic. That
needs to be done at the callsites.
hrtimer_force_reprogram() updates cpu_base::softirq_expires_next only when
the first expiring timer is a softirq timer and the soft interrupt is not
activated. That's wrong because cpu_base::softirq_expires_next is left
stale when the first expiring timer of all bases is a timer which expires
in hard interrupt context. hrtimer_interrupt() does never update
cpu_base::softirq_expires_next which is wrong too.
That becomes a problem when clock_settime() sets CLOCK_REALTIME forward and
the first soft expiring timer is in the CLOCK_REALTIME_SOFT base. Setting
CLOCK_REALTIME forward moves the clock MONOTONIC based expiry time of that
timer before the stale cpu_base::softirq_expires_next.
cpu_base::softirq_expires_next is cached to make the check for raising the
soft interrupt fast. In the above case the soft interrupt won't be raised
until clock monotonic reaches the stale cpu_base::softirq_expires_next
value. That's incorrect, but what's worse it that if the softirq timer
becomes the first expiring timer of all clock bases after the hard expiry
timer has been handled the reprogramming of the clockevent from
hrtimer_interrupt() will result in an interrupt storm. That happens because
the reprogramming does not use cpu_base::softirq_expires_next, it uses
__hrtimer_get_next_event() which returns the actual expiry time. Once clock
MONOTONIC reaches cpu_base::softirq_expires_next the soft interrupt is
raised and the storm subsides.
Change the logic in hrtimer_force_reprogram() to evaluate the soft and hard
bases seperately, update softirq_expires_next and handle the case when a
soft expiring timer is the first of all bases by comparing the expiry times
and updating the required cpu base fields. Split this functionality into a
separate function to be able to use it in hrtimer_interrupt() as well
without copy paste.
Fixes: 5da7016046 ("hrtimer: Implement support for softirq based hrtimers")
Reported-by: Mikael Beckius <mikael.beckius@windriver.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Mikael Beckius <mikael.beckius@windriver.com>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210223160240.27518-1-anna-maria@linutronix.de
- Documentation updates.
- Miscellaneous fixes.
- kfree_rcu() updates: Addition of mem_dump_obj() to provide allocator return
addresses to more easily locate bugs. This has a couple of RCU-related commits,
but is mostly MM. Was pulled in with akpm's agreement.
- Per-callback-batch tracking of numbers of callbacks,
which enables better debugging information and smarter
reactions to large numbers of callbacks.
- The first round of changes to allow CPUs to be runtime switched from and to
callback-offloaded state.
- CONFIG_PREEMPT_RT-related changes.
- RCU CPU stall warning updates.
- Addition of polling grace-period APIs for SRCU.
- Torture-test and torture-test scripting updates, including a "torture everything"
script that runs rcutorture, locktorture, scftorture, rcuscale, and refscale.
Plus does an allmodconfig build.
- nolibc fixes for the torture tests
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'core-rcu-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar:
"These are the latest RCU updates for v5.12:
- Documentation updates.
- Miscellaneous fixes.
- kfree_rcu() updates: Addition of mem_dump_obj() to provide
allocator return addresses to more easily locate bugs. This has a
couple of RCU-related commits, but is mostly MM. Was pulled in with
akpm's agreement.
- Per-callback-batch tracking of numbers of callbacks, which enables
better debugging information and smarter reactions to large numbers
of callbacks.
- The first round of changes to allow CPUs to be runtime switched
from and to callback-offloaded state.
- CONFIG_PREEMPT_RT-related changes.
- RCU CPU stall warning updates.
- Addition of polling grace-period APIs for SRCU.
- Torture-test and torture-test scripting updates, including a
"torture everything" script that runs rcutorture, locktorture,
scftorture, rcuscale, and refscale. Plus does an allmodconfig
build.
- nolibc fixes for the torture tests"
* tag 'core-rcu-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (130 commits)
percpu_ref: Dump mem_dump_obj() info upon reference-count underflow
rcu: Make call_rcu() print mem_dump_obj() info for double-freed callback
mm: Make mem_obj_dump() vmalloc() dumps include start and length
mm: Make mem_dump_obj() handle vmalloc() memory
mm: Make mem_dump_obj() handle NULL and zero-sized pointers
mm: Add mem_dump_obj() to print source of memory block
tools/rcutorture: Fix position of -lgcc in mkinitrd.sh
tools/nolibc: Fix position of -lgcc in the documented example
tools/nolibc: Emit detailed error for missing alternate syscall number definitions
tools/nolibc: Remove incorrect definitions of __ARCH_WANT_*
tools/nolibc: Get timeval, timespec and timezone from linux/time.h
tools/nolibc: Implement poll() based on ppoll()
tools/nolibc: Implement fork() based on clone()
tools/nolibc: Make getpgrp() fall back to getpgid(0)
tools/nolibc: Make dup2() rely on dup3() when available
tools/nolibc: Add the definition for dup()
rcutorture: Add rcutree.use_softirq=0 to RUDE01 and TASKS01
torture: Maintain torture-specific set of CPUs-online books
torture: Clean up after torture-test CPU hotplugging
rcutorture: Make object_debug also double call_rcu() heap object
...
- Instead of new drivers remove tango, sirf, u300 and atlas drivers
- Add suspend/resume support for microchip pit64b
- The usual fixes, improvements and cleanups here and there
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Merge tag 'timers-core-2021-02-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Time and timer updates:
- Instead of new drivers remove tango, sirf, u300 and atlas drivers
- Add suspend/resume support for microchip pit64b
- The usual fixes, improvements and cleanups here and there"
* tag 'timers-core-2021-02-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timens: Delete no-op time_ns_init()
alarmtimer: Update kerneldoc
clocksource/drivers/timer-microchip-pit64b: Add clocksource suspend/resume
clocksource/drivers/prima: Remove sirf prima driver
clocksource/drivers/atlas: Remove sirf atlas driver
clocksource/drivers/tango: Remove tango driver
clocksource/drivers/u300: Remove the u300 driver
dt-bindings: timer: nuvoton: Clarify that interrupt of timer 0 should be specified
clocksource/drivers/davinci: Move pr_fmt() before the includes
clocksource/drivers/efm32: Drop unused timer code
Pull RCU updates from Paul E. McKenney:
- Documentation updates.
- Miscellaneous fixes.
- kfree_rcu() updates: Addition of mem_dump_obj() to provide allocator return
addresses to more easily locate bugs. This has a couple of RCU-related commits,
but is mostly MM. Was pulled in with akpm's agreement.
- Per-callback-batch tracking of numbers of callbacks,
which enables better debugging information and smarter
reactions to large numbers of callbacks.
- The first round of changes to allow CPUs to be runtime switched from and to
callback-offloaded state.
- CONFIG_PREEMPT_RT-related changes.
- RCU CPU stall warning updates.
- Addition of polling grace-period APIs for SRCU.
- Torture-test and torture-test scripting updates, including a "torture everything"
script that runs rcutorture, locktorture, scftorture, rcuscale, and refscale.
Plus does an allmodconfig build.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The bug fixed by commit e3fab2f3de ("ntp: Fix RTC synchronization on
32-bit platforms") revealed an underlying issue: RTC synchronization may
happen anytime, even while the system is partially suspended.
On systems where the RTC is connected to an I2C bus, the I2C bus controller
may already or still be suspended, triggering a WARNING during suspend or
resume from s2ram:
WARNING: CPU: 0 PID: 124 at drivers/i2c/i2c-core.h:54 __i2c_transfer+0x634/0x680
i2c i2c-6: Transfer while suspended
[...]
Workqueue: events_power_efficient sync_hw_clock
[...]
(__i2c_transfer)
(i2c_transfer)
(regmap_i2c_read)
...
(da9063_rtc_set_time)
(rtc_set_time)
(sync_hw_clock)
(process_one_work)
Fix this race condition by using the freezable instead of the normal
power-efficient workqueue.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20210125143039.1051912-1-geert+renesas@glider.be
Due to an integer overflow, RTC synchronization now happens every 2s
instead of the intended 11 minutes. Fix this by forcing 64-bit
arithmetic for the sync period calculation.
Annotate the other place which multiplies seconds for consistency as well.
Fixes: c9e6189fb0 ("ntp: Make the RTC synchronization more reliable")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210111103956.290378-1-geert+renesas@glider.be
This commit addresses a few code-style nits in callback-offloading
toggling, including one that predates this toggling.
Cc: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a timer_curr_running() function that verifies that the
current code is running in the context of the specified timer's handler.
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
and fix a typo in the Kconfig help text.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'timers-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fixes from Ingo Molnar:
"Update/fix two CPU sanity checks in the hotplug and the boot code, and
fix a typo in the Kconfig help text.
[ Context: the first two commits are the result of an ongoing
annotation+review work of (intentional) tick_do_timer_cpu() data
races reported by KCSAN, but the annotations aren't fully cooked
yet ]"
* tag 'timers-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timekeeping: Fix spelling mistake in Kconfig "fullfill" -> "fulfill"
tick/sched: Remove bogus boot "safety" check
tick: Remove pointless cpu valid check in hotplug code
There is a spelling mistake in the Kconfig help text. Fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20201217171705.57586-1-colin.king@canonical.com
can_stop_idle_tick() checks whether the do_timer() duty has been taken over
by a CPU on boot. That's silly because the boot CPU always takes over with
the initial clockevent device.
But even if no CPU would have installed a clockevent and taken over the
duty then the question whether the tick on the current CPU can be stopped
or not is moot. In that case the current CPU would have no clockevent
either, so there would be nothing to keep ticking.
Remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20201206212002.725238293@linutronix.de
tick_handover_do_timer() which is invoked when a CPU is unplugged has a
check for cpumask_first(cpu_online_mask) when it tries to hand over the
tick update duty.
Checking the result of cpumask_first() there is pointless because if the
online mask is empty at this point, then this would be the last CPU in the
system going offline, which is impossible. There is always at least one CPU
remaining. If online mask would be really empty then the timer duty would
be the least of the resulting problems.
Remove the well meant check simply because it is pointless and confusing.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20201206212002.582579516@linutronix.de
This cleans up two ancient timer features that were never completed in
the past, CONFIG_GENERIC_CLOCKEVENTS and CONFIG_ARCH_USES_GETTIMEOFFSET.
There was only one user left for the ARCH_USES_GETTIMEOFFSET variant
of clocksource implementations, the ARM EBSA110 platform. Rather than
changing to use modern timekeeping, we remove the platform entirely as
Russell no longer uses his machine and nobody else seems to have one
any more.
The conditional code for using arch_gettimeoffset() is removed as
a result.
For CONFIG_GENERIC_CLOCKEVENTS, there are still a couple of platforms
not using clockevent drivers: parisc, ia64, most of m68k, and one
Arm platform. These all do timer ticks slighly differently, and this
gets cleaned up to the point they at least all call the same helper
function. Instead of most platforms using 'select GENERIC_CLOCKEVENTS'
in Kconfig, the polarity is now reversed, with the few remaining ones
selecting LEGACY_TIMER_TICK instead.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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Merge tag 'asm-generic-timers-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic
Pull asm-generic cross-architecture timer cleanup from Arnd Bergmann:
"This cleans up two ancient timer features that were never completed in
the past, CONFIG_GENERIC_CLOCKEVENTS and CONFIG_ARCH_USES_GETTIMEOFFSET.
There was only one user left for the ARCH_USES_GETTIMEOFFSET variant
of clocksource implementations, the ARM EBSA110 platform. Rather than
changing to use modern timekeeping, we remove the platform entirely as
Russell no longer uses his machine and nobody else seems to have one
any more.
The conditional code for using arch_gettimeoffset() is removed as a
result.
For CONFIG_GENERIC_CLOCKEVENTS, there are still a couple of platforms
not using clockevent drivers: parisc, ia64, most of m68k, and one Arm
platform. These all do timer ticks slighly differently, and this gets
cleaned up to the point they at least all call the same helper
function.
Instead of most platforms using 'select GENERIC_CLOCKEVENTS' in
Kconfig, the polarity is now reversed, with the few remaining ones
selecting LEGACY_TIMER_TICK instead"
* tag 'asm-generic-timers-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic:
timekeeping: default GENERIC_CLOCKEVENTS to enabled
timekeeping: remove xtime_update
m68k: remove timer_interrupt() function
m68k: change remaining timers to legacy_timer_tick
m68k: m68328: use legacy_timer_tick()
m68k: sun3/sun3c: use legacy_timer_tick
m68k: split heartbeat out of timer function
m68k: coldfire: use legacy_timer_tick()
parisc: use legacy_timer_tick
ARM: rpc: use legacy_timer_tick
ia64: convert to legacy_timer_tick
timekeeping: add CONFIG_LEGACY_TIMER_TICK
timekeeping: remove arch_gettimeoffset
net: remove am79c961a driver
ARM: remove ebsa110 platform
- migrate_disable/enable() support which originates from the RT tree and
is now a prerequisite for the new preemptible kmap_local() API which aims
to replace kmap_atomic().
- A fair amount of topology and NUMA related improvements
- Improvements for the frequency invariant calculations
- Enhanced robustness for the global CPU priority tracking and decision
making
- The usual small fixes and enhancements all over the place
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Merge tag 'sched-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Thomas Gleixner:
- migrate_disable/enable() support which originates from the RT tree
and is now a prerequisite for the new preemptible kmap_local() API
which aims to replace kmap_atomic().
- A fair amount of topology and NUMA related improvements
- Improvements for the frequency invariant calculations
- Enhanced robustness for the global CPU priority tracking and decision
making
- The usual small fixes and enhancements all over the place
* tag 'sched-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (61 commits)
sched/fair: Trivial correction of the newidle_balance() comment
sched/fair: Clear SMT siblings after determining the core is not idle
sched: Fix kernel-doc markup
x86: Print ratio freq_max/freq_base used in frequency invariance calculations
x86, sched: Use midpoint of max_boost and max_P for frequency invariance on AMD EPYC
x86, sched: Calculate frequency invariance for AMD systems
irq_work: Optimize irq_work_single()
smp: Cleanup smp_call_function*()
irq_work: Cleanup
sched: Limit the amount of NUMA imbalance that can exist at fork time
sched/numa: Allow a floating imbalance between NUMA nodes
sched: Avoid unnecessary calculation of load imbalance at clone time
sched/numa: Rename nr_running and break out the magic number
sched: Make migrate_disable/enable() independent of RT
sched/topology: Condition EAS enablement on FIE support
arm64: Rebuild sched domains on invariance status changes
sched/topology,schedutil: Wrap sched domains rebuild
sched/uclamp: Allow to reset a task uclamp constraint value
sched/core: Fix typos in comments
Documentation: scheduler: fix information on arch SD flags, sched_domain and sched_debug
...
Core:
- Robustness improvements for the NOHZ tick management
- Fixes and consolidation of the NTP/RTC synchronization code
- Small fixes and improvements in various places
- A set of function documentation udpates and fixes
Drivers:
- Cleanups and improvements in various clocksoure/event drivers
- Removal of the EZChip NPS clocksource driver as the platfrom support
was removed from ARC
- The usual set of new device tree binding and json conversions
- The RTC driver which have been acked by the RTC maintainer:
- Fix a long standing bug in the MC146818 library code which can cause
reading garbage during the RTC internal update.
- The changes related to the NTP/RTC consolidation work.
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Merge tag 'timers-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timers and timekeeping updates from Thomas Gleixner:
"Core:
- Robustness improvements for the NOHZ tick management
- Fixes and consolidation of the NTP/RTC synchronization code
- Small fixes and improvements in various places
- A set of function documentation udpates and fixes
Drivers:
- Cleanups and improvements in various clocksoure/event drivers
- Removal of the EZChip NPS clocksource driver as the platfrom
support was removed from ARC
- The usual set of new device tree binding and json conversions
- The RTC driver which have been acked by the RTC maintainer:
* fix a long standing bug in the MC146818 library code which can
cause reading garbage during the RTC internal update.
* changes related to the NTP/RTC consolidation work"
* tag 'timers-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (46 commits)
ntp: Fix prototype in the !CONFIG_GENERIC_CMOS_UPDATE case
tick/sched: Make jiffies update quick check more robust
ntp: Consolidate the RTC update implementation
ntp: Make the RTC sync offset less obscure
ntp, rtc: Move rtc_set_ntp_time() to ntp code
ntp: Make the RTC synchronization more reliable
rtc: core: Make the sync offset default more realistic
rtc: cmos: Make rtc_cmos sync offset correct
rtc: mc146818: Reduce spinlock section in mc146818_set_time()
rtc: mc146818: Prevent reading garbage
clocksource/drivers/sh_cmt: Fix potential deadlock when calling runtime PM
clocksource/drivers/arm_arch_timer: Correct fault programming of CNTKCTL_EL1.EVNTI
clocksource/drivers/arm_arch_timer: Use stable count reader in erratum sne
clocksource/drivers/dw_apb_timer_of: Add error handling if no clock available
clocksource/drivers/riscv: Make RISCV_TIMER depends on RISCV_SBI
clocksource/drivers/ingenic: Fix section mismatch
clocksource/drivers/cadence_ttc: Fix memory leak in ttc_setup_clockevent()
dt-bindings: timer: renesas: tmu: Convert to json-schema
dt-bindings: timer: renesas: tmu: Document r8a774e1 bindings
clocksource/drivers/orion: Add missing clk_disable_unprepare() on error path
...
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Merge tag 'fixes-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull misc fixes from Christian Brauner:
"This contains several fixes which felt worth being combined into a
single branch:
- Use put_nsproxy() instead of open-coding it switch_task_namespaces()
- Kirill's work to unify lifecycle management for all namespaces. The
lifetime counters are used identically for all namespaces types.
Namespaces may of course have additional unrelated counters and
these are not altered. This work allows us to unify the type of the
counters and reduces maintenance cost by moving the counter in one
place and indicating that basic lifetime management is identical
for all namespaces.
- Peilin's fix adding three byte padding to Dmitry's
PTRACE_GET_SYSCALL_INFO uapi struct to prevent an info leak.
- Two smal patches to convert from the /* fall through */ comment
annotation to the fallthrough keyword annotation which I had taken
into my branch and into -next before df561f6688 ("treewide: Use
fallthrough pseudo-keyword") made it upstream which fixed this
tree-wide.
Since I didn't want to invalidate all testing for other commits I
didn't rebase and kept them"
* tag 'fixes-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
nsproxy: use put_nsproxy() in switch_task_namespaces()
sys: Convert to the new fallthrough notation
signal: Convert to the new fallthrough notation
time: Use generic ns_common::count
cgroup: Use generic ns_common::count
mnt: Use generic ns_common::count
user: Use generic ns_common::count
pid: Use generic ns_common::count
ipc: Use generic ns_common::count
uts: Use generic ns_common::count
net: Use generic ns_common::count
ns: Add a common refcount into ns_common
ptrace: Prevent kernel-infoleak in ptrace_get_syscall_info()
The quick check in tick_do_update_jiffies64() whether jiffies need to be
updated is not really correct under all circumstances and on all
architectures, especially not on 32bit systems.
The quick check does:
if (now < READ_ONCE(tick_next_period))
return;
and the counterpart in the update is:
WRITE_ONCE(tick_next_period, next_update_time);
This has two problems:
1) On weakly ordered architectures there is no guarantee that the stores
before the WRITE_ONCE() are visible which means that other CPUs can
operate on a stale jiffies value.
2) On 32bit the store of tick_next_period which is an u64 is split into
two 32bit stores. If the first 32bit store advances tick_next_period
far out and the second 32bit store is delayed (virt, NMI ...) then
jiffies will become stale until the second 32bit store happens.
Address this by seperating the handling for 32bit and 64bit.
On 64bit problem #1 is addressed by replacing READ_ONCE() / WRITE_ONCE()
with smp_load_acquire() / smp_store_release().
On 32bit problem #2 is addressed by protecting the quick check with the
jiffies sequence counter. The load and stores can be plain because the
sequence count mechanics provides the required barriers already.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/87czzpc02w.fsf@nanos.tec.linutronix.de
The code for the legacy RTC and the RTC class based update are pretty much
the same. Consolidate the common parts into one function and just invoke
the actual setter functions.
For RTC class based devices the update code checks whether the offset is
valid for the device, which is usually not the case for the first
invocation. If it's not the same it stores the correct offset and lets the
caller try again. That's not much different from the previous approach
where the first invocation had a pretty low probability to actually hit the
allowed window.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201206220542.355743355@linutronix.de
The current RTC set_offset_nsec value is not really intuitive to
understand.
tsched twrite(t2.tv_sec - 1) t2 (seconds increment)
The offset is calculated from twrite based on the assumption that t2 -
twrite == 1s. That means for the MC146818 RTC the offset needs to be
negative so that the write happens 500ms before t2.
It's easier to understand when the whole calculation is based on t2. That
avoids negative offsets and the meaning is obvious:
t2 - twrite: The time defined by the chip when seconds increment
after the write.
twrite - tsched: The time for the transport to the point where the chip
is updated.
==> set_offset_nsec = t2 - tsched
ttransport = twrite - tsched
tRTCinc = t2 - twrite
==> set_offset_nsec = ttransport + tRTCinc
tRTCinc is a chip property and can be obtained from the data sheet.
ttransport depends on how the RTC is connected. It is close to 0 for
directly accessible RTCs. For RTCs behind a slow bus, e.g. i2c, it's the
time required to send the update over the bus. This can be estimated or
even calibrated, but that's a different problem.
Adjust the implementation and update comments accordingly.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201206220542.263204937@linutronix.de
rtc_set_ntp_time() is not really RTC functionality as the code is just a
user of RTC. Move it into the NTP code which allows further cleanups.
Requested-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201206220542.166871172@linutronix.de
Miroslav reported that the periodic RTC synchronization in the NTP code
fails more often than not to hit the specified update window.
The reason is that the code uses delayed_work to schedule the update which
needs to be in thread context as the underlying RTC might be connected via
a slow bus, e.g. I2C. In the update function it verifies whether the
current time is correct vs. the requirements of the underlying RTC.
But delayed_work is using the timer wheel for scheduling which is
inaccurate by design. Depending on the distance to the expiry the wheel
gets less granular to allow batching and to avoid the cascading of the
original timer wheel. See 500462a9de ("timers: Switch to a non-cascading
wheel") and the code for further details.
The code already deals with this by splitting the 660 seconds period into a
long 659 seconds timer and then retrying with a smaller delta.
But looking at the actual granularities of the timer wheel (which depend on
the HZ configuration) the 659 seconds timer ends up in an outer wheel level
and is affected by a worst case granularity of:
HZ Granularity
1000 32s
250 16s
100 40s
So the initial timer can be already off by max 12.5% which is not a big
issue as the period of the sync is defined as ~11 minutes.
The fine grained second attempt schedules to the desired update point with
a timer expiring less than a second from now. Depending on the actual delta
and the HZ setting even the second attempt can end up in outer wheel levels
which have a large enough granularity to make the correctness check fail.
As this is a fundamental property of the timer wheel there is no way to
make this more accurate short of iterating in one jiffies steps towards the
update point.
Switch it to an hrtimer instead which schedules the actual update work. The
hrtimer will expire precisely (max 1 jiffie delay when high resolution
timers are not available). The actual scheduling delay of the work is the
same as before.
The update is triggered from do_adjtimex() which is a bit racy but not much
more racy than it was before:
if (ntp_synced())
queue_delayed_work(system_power_efficient_wq, &sync_work, 0);
which is racy when the work is currently executed and has not managed to
reschedule itself.
This becomes now:
if (ntp_synced() && !hrtimer_is_queued(&sync_hrtimer))
queue_work(system_power_efficient_wq, &sync_work, 0);
which is racy when the hrtimer has expired and the work is currently
executed and has not yet managed to rearm the hrtimer.
Not a big problem as it just schedules work for nothing.
The new implementation has a safe guard in place to catch the case where
the hrtimer is queued on entry to the work function and avoids an extra
update attempt of the RTC that way.
Reported-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Miroslav Lichvar <mlichvar@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201206220542.062910520@linutronix.de
Get rid of the __call_single_node union and clean up the API a little
to avoid external code relying on the structure layout as much.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
The variable tick_period is initialized to NSEC_PER_TICK / HZ during boot
and never updated again.
If NSEC_PER_TICK is not an integer multiple of HZ this computation is less
accurate than TICK_NSEC which has proper rounding in place.
Aside of the inaccuracy there is no reason for having this variable at
all. It's just a pointless indirection and all usage sites can just use the
TICK_NSEC constant.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.766643526@linutronix.de
calc_load_global() does not need the sequence count protection.
[ tglx: Split it up properly and added comments ]
Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.660902274@linutronix.de
If jiffies are up to date already (caller lost the race against another
CPU) there is no point to change the sequence count. Doing that just forces
other CPUs into the seqcount retry loop in tick_nohz_next_event() for
nothing.
Just bail out early.
[ tglx: Rewrote most of it ]
Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.462195901@linutronix.de
No point in doing calculations.
tick_next_period = last_jiffies_update + tick_period
Just check whether now is before tick_next_period to figure out whether
jiffies need an update.
Add a comment why the intentional data race in the quick check is safe or
not so safe in a 32bit corner case and why we don't worry about it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.337366695@linutronix.de
tick_broadcast_setup_oneshot() accesses tick_next_period twice without any
serialization. This is wrong in two aspects:
- Reading it twice might make the broadcast data inconsistent if the
variable is updated concurrently.
- On 32bit systems the access might see an partial update
Protect it with jiffies_lock. That's safe as none of the callchains leading
up to this function can create a lock ordering violation:
timer interrupt
run_local_timers()
hrtimer_run_queues()
hrtimer_switch_to_hres()
tick_init_highres()
tick_switch_to_oneshot()
tick_broadcast_switch_to_oneshot()
or
tick_check_oneshot_change()
tick_nohz_switch_to_nohz()
tick_switch_to_oneshot()
tick_broadcast_switch_to_oneshot()
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.061341507@linutronix.de
timens_on_fork() always return 0, and maybe not
need to judge the return value in copy_namespaces().
So make timens_on_fork() return nothing and do not
judge its return val in copy_namespaces().
Signed-off-by: Hui Su <sh_def@163.com>
Link: https://lore.kernel.org/r/20201117161750.GA45121@rlk
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The hrtimer_get_remaining() markup is documenting, instead,
__hrtimer_get_remaining(), as it is placed at the C file.
In order to properly document it, a kernel-doc markup is needed together
with the function prototype. So, add a new one, while preserving the
existing one, just fixing the function name.
The hrtimer_is_queued prototype has a typo: it is using
'=' instead of '-' to split: identifier - description
as required by kernel-doc markup.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/9dc87808c2fd07b7e050bafcd033c5ef05808fea.1605521731.git.mchehab+huawei@kernel.org
No users outside of the timer code. Move the caller below this function to
avoid a pointless forward declaration.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The kernel-doc parser complains:
kernel/time/timekeeping.c:1543: warning: Function parameter or member
'ts' not described in 'read_persistent_clock64'
kernel/time/timekeeping.c:764: warning: Function parameter or member
'tk' not described in 'timekeeping_forward_now'
kernel/time/timekeeping.c:1331: warning: Function parameter or member
'ts' not described in 'timekeeping_inject_offset'
kernel/time/timekeeping.c:1331: warning: Excess function parameter 'tv'
description in 'timekeeping_inject_offset'
Add the missing parameter documentations and rename the 'tv' parameter of
timekeeping_inject_offset() to 'ts' so it matches the implemention.
[ tglx: Reworded a few docs and massaged changelog ]
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-5-git-send-email-alex.shi@linux.alibaba.com
Address the following kernel-doc markup warnings:
kernel/time/timekeeping.c:1563: warning: Function parameter or member
'wall_time' not described in 'read_persistent_wall_and_boot_offset'
kernel/time/timekeeping.c:1563: warning: Function parameter or member
'boot_offset' not described in 'read_persistent_wall_and_boot_offset'
The parameters are described but miss the leading '@' and the colon after
the parameter names.
[ tglx: Massaged changelog ]
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-6-git-send-email-alex.shi@linux.alibaba.com
The kernel-doc parser complains about:
kernel/time/timekeeping.c:651: warning: Function parameter or member
'nb' not described in 'pvclock_gtod_register_notifier'
kernel/time/timekeeping.c:670: warning: Function parameter or member
'nb' not described in 'pvclock_gtod_unregister_notifier'
Add the missing parameter explanations.
[ tglx: Massaged changelog ]
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-3-git-send-email-alex.shi@linux.alibaba.com
Alex reported the following warning:
kernel/time/timekeeping.c:464: warning: Function parameter or member
'tkf' not described in '__ktime_get_fast_ns'
which is not entirely correct because the documented function is
ktime_get_mono_fast_ns() which does not have a parameter, but the
kernel-doc parser looks at the function declaration which follows the
comment and complains about the missing parameter documentation.
Aside of that the documentation for the rest of the NMI safe accessors is
either incomplete or missing.
- Move the function documentation to the right place
- Fixup the references and inconsistencies
- Add the missing documentation for ktime_get_raw_fast_ns()
Reported-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Address the following warning:
kernel/time/timekeeping.c:415: warning: Function parameter or member
'tkf' not described in 'update_fast_timekeeper'
[ tglx: Remove the bogus ktime_get_mono_fast_ns() part ]
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-2-git-send-email-alex.shi@linux.alibaba.com
Various static functions in the timekeeping code have function comments
which pretend to be kernel-doc, but are incomplete and trigger parser
warnings.
As these functions are local to the timekeeping core code there is no need
to expose them via kernel-doc.
Remove the double star kernel-doc marker and remove excess newlines.
[ tglx: Massaged changelog and removed excess newlines ]
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-4-git-send-email-alex.shi@linux.alibaba.com
Address these kernel-doc warnings:
kernel/time/timeconv.c:79: warning: Function parameter or member
'totalsecs' not described in 'time64_to_tm'
kernel/time/timeconv.c:79: warning: Function parameter or member
'offset' not described in 'time64_to_tm'
kernel/time/timeconv.c:79: warning: Function parameter or member
'result' not described in 'time64_to_tm'
The parameters are described but lack colons after the parameter name.
[ tglx: Massaged changelog ]
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-1-git-send-email-alex.shi@linux.alibaba.com
PREEMPT_RT does not spin and wait until a running timer completes its
callback but instead it blocks on a sleeping lock to prevent a livelock in
the case that the task waiting for the callback completion preempted the
callback.
This cannot be done for timers flagged with TIMER_IRQSAFE. These timers can
be canceled from an interrupt disabled context even on RT kernels.
The expiry callback of such timers is invoked with interrupts disabled so
there is no need to use the expiry lock mechanism because obviously the
callback cannot be preempted even on RT kernels.
Do not use the timer_base::expiry_lock mechanism when waiting for a running
callback to complete if the timer is flagged with TIMER_IRQSAFE.
Also add a lockdep assertion for RT kernels to validate that the expiry
lock mechanism is always invoked in preemptible context.
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201103190937.hga67rqhvknki3tp@linutronix.de
Use the "%ps" printk format string to resolve symbol names.
This works on all platforms, including ia64, ppc64 and parisc64 on which
one needs to dereference pointers to function descriptors instead of
function pointers.
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201104163401.GA3984@ls3530.fritz.box
Almost all machines use GENERIC_CLOCKEVENTS, so it feels wrong to
require each one to select that symbol manually.
Instead, enable it whenever CONFIG_LEGACY_TIMER_TICK is disabled as
a simplification. It should be possible to select both
GENERIC_CLOCKEVENTS and LEGACY_TIMER_TICK from an architecture now
and decide at runtime between the two.
For the clockevents arch-support.txt file, this means that additional
architectures are marked as TODO when they have at least one machine
that still uses LEGACY_TIMER_TICK, rather than being marked 'ok' when
at least one machine has been converted. This means that both m68k and
arm (for riscpc) revert to TODO.
At this point, we could just always enable CONFIG_GENERIC_CLOCKEVENTS
rather than leaving it off when not needed. I built an m68k
defconfig kernel (using gcc-10.1.0) and found that this would add
around 5.5KB in kernel image size:
text data bss dec hex filename
3861936 1092236 196656 5150828 4e986c obj-m68k/vmlinux-no-clockevent
3866201 1093832 196184 5156217 4ead79 obj-m68k/vmlinux-clockevent
On Arm (MACH_RPC), that difference appears to be twice as large,
around 11KB on top of an 6MB vmlinux.
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
There are no more users of xtime_update aside from legacy_timer_tick(),
so fold it into that function and remove the declaration.
update_process_times() is now only called inside of the kernel/time/
code, so the declaration can be moved there.
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
All platforms that currently do not use generic clockevents roughly call
the same set of functions in their timer interrupts: xtime_update(),
update_process_times() and profile_tick(), sometimes in a different
sequence.
Add a helper function that performs all three of them, to make the
callers more uniform and simplify the interface.
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
With Arm EBSA110 gone, nothing uses it any more, so the corresponding
code and the Kconfig option can be removed.
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
UBSAN reports:
Undefined behaviour in ./include/linux/time64.h:127:27
signed integer overflow:
17179869187 * 1000000000 cannot be represented in type 'long long int'
Call Trace:
timespec64_to_ns include/linux/time64.h:127 [inline]
set_cpu_itimer+0x65c/0x880 kernel/time/itimer.c:180
do_setitimer+0x8e/0x740 kernel/time/itimer.c:245
__x64_sys_setitimer+0x14c/0x2c0 kernel/time/itimer.c:336
do_syscall_64+0xa1/0x540 arch/x86/entry/common.c:295
Commit bd40a17576 ("y2038: itimer: change implementation to timespec64")
replaced the original conversion which handled time clamping correctly with
timespec64_to_ns() which has no overflow protection.
Fix it in timespec64_to_ns() as this is not necessarily limited to the
usage in itimers.
[ tglx: Added comment and adjusted the fixes tag ]
Fixes: 361a3bf005 ("time64: Add time64.h header and define struct timespec64")
Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/1598952616-6416-1-git-send-email-prime.zeng@hisilicon.com
Since sched_clock_read_begin() and sched_clock_read_retry() are called
by notrace function sched_clock(), they shouldn't be traceable either,
or else ftrace_graph_caller will run into a dead loop on the path
as below (arm for instance):
ftrace_graph_caller()
prepare_ftrace_return()
function_graph_enter()
ftrace_push_return_trace()
trace_clock_local()
sched_clock()
sched_clock_read_begin/retry()
Fixes: 1b86abc1c6 ("sched_clock: Expose struct clock_read_data")
Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200929082027.16787-1-quanyang.wang@windriver.com
Use the new api and associate the seqcounter to the jiffies_lock enabling
lockdep support - although for this particular case the write-side locking
and non-preemptibility are quite obvious.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201021190749.19363-1-dave@stgolabs.net
With the removal of the interrupt perturbations in previous random32
change (random32: make prandom_u32() output unpredictable), the PRNG
has become 100% deterministic again. While SipHash is expected to be
way more robust against brute force than the previous Tausworthe LFSR,
there's still the risk that whoever has even one temporary access to
the PRNG's internal state is able to predict all subsequent draws till
the next reseed (roughly every minute). This may happen through a side
channel attack or any data leak.
This patch restores the spirit of commit f227e3ec3b ("random32: update
the net random state on interrupt and activity") in that it will perturb
the internal PRNG's statee using externally collected noise, except that
it will not pick that noise from the random pool's bits nor upon
interrupt, but will rather combine a few elements along the Tx path
that are collectively hard to predict, such as dev, skb and txq
pointers, packet length and jiffies values. These ones are combined
using a single round of SipHash into a single long variable that is
mixed with the net_rand_state upon each invocation.
The operation was inlined because it produces very small and efficient
code, typically 3 xor, 2 add and 2 rol. The performance was measured
to be the same (even very slightly better) than before the switch to
SipHash; on a 6-core 12-thread Core i7-8700k equipped with a 40G NIC
(i40e), the connection rate dropped from 556k/s to 555k/s while the
SYN cookie rate grew from 5.38 Mpps to 5.45 Mpps.
Link: https://lore.kernel.org/netdev/20200808152628.GA27941@SDF.ORG/
Cc: George Spelvin <lkml@sdf.org>
Cc: Amit Klein <aksecurity@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: tytso@mit.edu
Cc: Florian Westphal <fw@strlen.de>
Cc: Marc Plumb <lkml.mplumb@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Non-cryptographic PRNGs may have great statistical properties, but
are usually trivially predictable to someone who knows the algorithm,
given a small sample of their output. An LFSR like prandom_u32() is
particularly simple, even if the sample is widely scattered bits.
It turns out the network stack uses prandom_u32() for some things like
random port numbers which it would prefer are *not* trivially predictable.
Predictability led to a practical DNS spoofing attack. Oops.
This patch replaces the LFSR with a homebrew cryptographic PRNG based
on the SipHash round function, which is in turn seeded with 128 bits
of strong random key. (The authors of SipHash have *not* been consulted
about this abuse of their algorithm.) Speed is prioritized over security;
attacks are rare, while performance is always wanted.
Replacing all callers of prandom_u32() is the quick fix.
Whether to reinstate a weaker PRNG for uses which can tolerate it
is an open question.
Commit f227e3ec3b ("random32: update the net random state on interrupt
and activity") was an earlier attempt at a solution. This patch replaces
it.
Reported-by: Amit Klein <aksecurity@gmail.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: tytso@mit.edu
Cc: Florian Westphal <fw@strlen.de>
Cc: Marc Plumb <lkml.mplumb@gmail.com>
Fixes: f227e3ec3b ("random32: update the net random state on interrupt and activity")
Signed-off-by: George Spelvin <lkml@sdf.org>
Link: https://lore.kernel.org/netdev/20200808152628.GA27941@SDF.ORG/
[ willy: partial reversal of f227e3ec3b5c; moved SIPROUND definitions
to prandom.h for later use; merged George's prandom_seed() proposal;
inlined siprand_u32(); replaced the net_rand_state[] array with 4
members to fix a build issue; cosmetic cleanups to make checkpatch
happy; fixed RANDOM32_SELFTEST build ]
Signed-off-by: Willy Tarreau <w@1wt.eu>
Pull RCU changes from Ingo Molnar:
- Debugging for smp_call_function()
- RT raw/non-raw lock ordering fixes
- Strict grace periods for KASAN
- New smp_call_function() torture test
- Torture-test updates
- Documentation updates
- Miscellaneous fixes
[ This doesn't actually pull the tag - I've dropped the last merge from
the RCU branch due to questions about the series. - Linus ]
* tag 'core-rcu-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (77 commits)
smp: Make symbol 'csd_bug_count' static
kernel/smp: Provide CSD lock timeout diagnostics
smp: Add source and destination CPUs to __call_single_data
rcu: Shrink each possible cpu krcp
rcu/segcblist: Prevent useless GP start if no CBs to accelerate
torture: Add gdb support
rcutorture: Allow pointer leaks to test diagnostic code
rcutorture: Hoist OOM registry up one level
refperf: Avoid null pointer dereference when buf fails to allocate
rcutorture: Properly synchronize with OOM notifier
rcutorture: Properly set rcu_fwds for OOM handling
torture: Add kvm.sh --help and update help message
rcutorture: Add CONFIG_PROVE_RCU_LIST to TREE05
torture: Update initrd documentation
rcutorture: Replace HTTP links with HTTPS ones
locktorture: Make function torture_percpu_rwsem_init() static
torture: document --allcpus argument added to the kvm.sh script
rcutorture: Output number of elapsed grace periods
rcutorture: Remove KCSAN stubs
rcu: Remove unused "cpu" parameter from rcu_report_qs_rdp()
...
- Add deadlock detection for recursive read-locks. The rationale is outlined
in:
224ec489d3: ("lockdep/Documention: Recursive read lock detection reasoning")
The main deadlock pattern we want to detect is:
TASK A: TASK B:
read_lock(X);
write_lock(X);
read_lock_2(X);
- Add "latch sequence counters" (seqcount_latch_t):
A sequence counter variant where the counter even/odd value is used to
switch between two copies of protected data. This allows the read path,
typically NMIs, to safely interrupt the write side critical section.
We utilize this new variant for sched-clock, and to make x86 TSC handling safer.
- Other seqlock cleanups, fixes and enhancements
- KCSAN updates
- LKMM updates
- Misc updates, cleanups and fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'locking-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
"These are the locking updates for v5.10:
- Add deadlock detection for recursive read-locks.
The rationale is outlined in commit 224ec489d3 ("lockdep/
Documention: Recursive read lock detection reasoning")
The main deadlock pattern we want to detect is:
TASK A: TASK B:
read_lock(X);
write_lock(X);
read_lock_2(X);
- Add "latch sequence counters" (seqcount_latch_t):
A sequence counter variant where the counter even/odd value is used
to switch between two copies of protected data. This allows the
read path, typically NMIs, to safely interrupt the write side
critical section.
We utilize this new variant for sched-clock, and to make x86 TSC
handling safer.
- Other seqlock cleanups, fixes and enhancements
- KCSAN updates
- LKMM updates
- Misc updates, cleanups and fixes"
* tag 'locking-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (67 commits)
lockdep: Revert "lockdep: Use raw_cpu_*() for per-cpu variables"
lockdep: Fix lockdep recursion
lockdep: Fix usage_traceoverflow
locking/atomics: Check atomic-arch-fallback.h too
locking/seqlock: Tweak DEFINE_SEQLOCK() kernel doc
lockdep: Optimize the memory usage of circular queue
seqlock: Unbreak lockdep
seqlock: PREEMPT_RT: Do not starve seqlock_t writers
seqlock: seqcount_LOCKNAME_t: Introduce PREEMPT_RT support
seqlock: seqcount_t: Implement all read APIs as statement expressions
seqlock: Use unique prefix for seqcount_t property accessors
seqlock: seqcount_LOCKNAME_t: Standardize naming convention
seqlock: seqcount latch APIs: Only allow seqcount_latch_t
rbtree_latch: Use seqcount_latch_t
x86/tsc: Use seqcount_latch_t
timekeeping: Use seqcount_latch_t
time/sched_clock: Use seqcount_latch_t
seqlock: Introduce seqcount_latch_t
mm/swap: Do not abuse the seqcount_t latching API
time/sched_clock: Use raw_read_seqcount_latch() during suspend
...
Core:
- Early boot support for the NMI safe timekeeper by utilizing
local_clock() up to the point where timekeeping is initialized. This
allows printk() to store multiple timestamps in the ringbuffer which is
useful for coordinating dmesg information across a fleet of machines.
- Provide a multi-timestamp accessor for printk()
- Make timer init more robust by checking for invalid timer flags.
- Comma vs. semicolon fixes
Drivers:
- Support for new platforms in existing drivers (SP804 and Renesas CMT)
- Comma vs. semicolon fixes
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Merge tag 'timers-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timekeeping updates from Thomas Gleixner:
"Updates for timekeeping, timers and related drivers:
Core:
- Early boot support for the NMI safe timekeeper by utilizing
local_clock() up to the point where timekeeping is initialized.
This allows printk() to store multiple timestamps in the ringbuffer
which is useful for coordinating dmesg information across a fleet
of machines.
- Provide a multi-timestamp accessor for printk()
- Make timer init more robust by checking for invalid timer flags.
- Comma vs semicolon fixes
Drivers:
- Support for new platforms in existing drivers (SP804 and Renesas
CMT)
- Comma vs semicolon fixes
* tag 'timers-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
clocksource/drivers/armada-370-xp: Use semicolons rather than commas to separate statements
clocksource/drivers/mps2-timer: Use semicolons rather than commas to separate statements
timers: Mask invalid flags in do_init_timer()
clocksource/drivers/sp804: Enable Hisilicon sp804 timer 64bit mode
clocksource/drivers/sp804: Add support for Hisilicon sp804 timer
clocksource/drivers/sp804: Support non-standard register offset
clocksource/drivers/sp804: Prepare for support non-standard register offset
clocksource/drivers/sp804: Remove a mismatched comment
clocksource/drivers/sp804: Delete the leading "__" of some functions
clocksource/drivers/sp804: Remove unused sp804_timer_disable() and timer-sp804.h
clocksource/drivers/sp804: Cleanup clk_get_sys()
dt-bindings: timer: renesas,cmt: Document r8a774e1 CMT support
dt-bindings: timer: renesas,cmt: Document r8a7742 CMT support
alarmtimer: Convert comma to semicolon
timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper
timekeeping: Utilize local_clock() for NMI safe timekeeper during early boot
Pull v5.10 RCU changes from Paul E. McKenney:
- Debugging for smp_call_function().
- Strict grace periods for KASAN. The point of this series is to find
RCU-usage bugs, so the corresponding new RCU_STRICT_GRACE_PERIOD
Kconfig option depends on both DEBUG_KERNEL and RCU_EXPERT, and is
further disabled by dfefault. Finally, the help text includes
a goodly list of scary caveats.
- New smp_call_function() torture test.
- Torture-test updates.
- Documentation updates.
- Miscellaneous fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
do_init_timer() accepts any combination of timer flags handed in by the
caller without a sanity check, but only TIMER_DEFFERABLE, TIMER_PINNED and
TIMER_IRQSAFE are valid.
If the supplied flags have other bits set, this could result in
malfunction. If bits are set in TIMER_CPUMASK the first timer usage could
deference a cpu base which is outside the range of possible CPUs. If
TIMER_MIGRATION is set, then the switch_timer_base() will live lock.
Prevent that with a sanity check which warns when invalid flags are
supplied and masks them out.
[ tglx: Made it WARN_ON_ONCE() and added context to the changelog ]
Signed-off-by: Qianli Zhao <zhaoqianli@xiaomi.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/9d79a8aa4eb56713af7379f99f062dedabcde140.1597326756.git.zhaoqianli@xiaomi.com
This should make it harder for the kernel to corrupt the debug object
descriptor, used to call functions to fixup state and track debug objects,
by moving the structure to read-only memory.
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200815004027.2046113-3-swboyd@chromium.org
Latch sequence counters are a multiversion concurrency control mechanism
where the seqcount_t counter even/odd value is used to switch between
two data storage copies. This allows the seqcount_t read path to safely
interrupt its write side critical section (e.g. from NMIs).
Initially, latch sequence counters were implemented as a single write
function, raw_write_seqcount_latch(), above plain seqcount_t. The read
path was expected to use plain seqcount_t raw_read_seqcount().
A specialized read function was later added, raw_read_seqcount_latch(),
and became the standardized way for latch read paths. Having unique read
and write APIs meant that latch sequence counters are basically a data
type of their own -- just inappropriately overloading plain seqcount_t.
The seqcount_latch_t data type was thus introduced at seqlock.h.
Use that new data type instead of seqcount_raw_spinlock_t. This ensures
that only latch-safe APIs are to be used with the sequence counter.
Note that the use of seqcount_raw_spinlock_t was not very useful in the
first place. Only the "raw_" subset of seqcount_t APIs were used at
timekeeping.c. This subset was created for contexts where lockdep cannot
be used. seqcount_LOCKTYPE_t's raison d'être -- verifying that the
seqcount_t writer serialization lock is held -- cannot thus be done.
References: 0c3351d451 ("seqlock: Use raw_ prefix instead of _no_lockdep")
References: 55f3560df9 ("seqlock: Extend seqcount API with associated locks")
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200827114044.11173-6-a.darwish@linutronix.de
Latch sequence counters have unique read and write APIs, and thus
seqcount_latch_t was recently introduced at seqlock.h.
Use that new data type instead of plain seqcount_t. This adds the
necessary type-safety and ensures only latching-safe seqcount APIs are
to be used.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200827114044.11173-5-a.darwish@linutronix.de
sched_clock uses seqcount_t latching to switch between two storage
places protected by the sequence counter. This allows it to have
interruptible, NMI-safe, seqcount_t write side critical sections.
Since 7fc26327b7 ("seqlock: Introduce raw_read_seqcount_latch()"),
raw_read_seqcount_latch() became the standardized way for seqcount_t
latch read paths. Due to the dependent load, it has one read memory
barrier less than the currently used raw_read_seqcount() API.
Use raw_read_seqcount_latch() for the suspend path.
Commit aadd6e5caa ("time/sched_clock: Use raw_read_seqcount_latch()")
missed changing that instance of raw_read_seqcount().
References: 1809bfa44e ("timers, sched/clock: Avoid deadlock during read from NMI")
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200715092345.GA231464@debian-buster-darwi.lab.linutronix.de
Replace a comma between expression statements by a semicolon.
Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20200818062651.21680-1-vulab@iscas.ac.cn
Currently, can_stop_idle_tick() prints "NOHZ: local_softirq_pending HH"
(where "HH" is the hexadecimal softirq vector number) when one or more
non-RCU softirq handlers are still enabled when checking to stop the
scheduler-tick interrupt. This message is not as enlightening as one
might hope, so this commit changes it to "NOHZ tick-stop error: Non-RCU
local softirq work is pending, handler #HH".
Reported-by: Andy Lutomirski <luto@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
printk wants to store various timestamps (MONOTONIC, REALTIME, BOOTTIME) to
make correlation of dmesg from several systems easier.
Provide an interface to retrieve all three timestamps in one go.
There are some caveats:
1) Boot time and late sleep time injection
Boot time is a racy access on 32bit systems if the sleep time injection
happens late during resume and not in timekeeping_resume(). That could be
avoided by expanding struct tk_read_base with boot offset for 32bit and
adding more overhead to the update. As this is a hard to observe once per
resume event which can be filtered with reasonable effort using the
accurate mono/real timestamps, it's probably not worth the trouble.
Aside of that it might be possible on 32 and 64 bit to observe the
following when the sleep time injection happens late:
CPU 0 CPU 1
timekeeping_resume()
ktime_get_fast_timestamps()
mono, real = __ktime_get_real_fast()
inject_sleep_time()
update boot offset
boot = mono + bootoffset;
That means that boot time already has the sleep time adjustment, but
real time does not. On the next readout both are in sync again.
Preventing this for 64bit is not really feasible without destroying the
careful cache layout of the timekeeper because the sequence count and
struct tk_read_base would then need two cache lines instead of one.
2) Suspend/resume timestamps
Access to the time keeper clock source is disabled accross the innermost
steps of suspend/resume. The accessors still work, but the timestamps
are frozen until time keeping is resumed which happens very early.
For regular suspend/resume there is no observable difference vs. sched
clock, but it might affect some of the nasty low level debug printks.
OTOH, access to sched clock is not guaranteed accross suspend/resume on
all systems either so it depends on the hardware in use.
If that turns out to be a real problem then this could be mitigated by
using sched clock in a similar way as during early boot. But it's not as
trivial as on early boot because it needs some careful protection
against the clock monotonic timestamp jumping backwards on resume.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200814115512.159981360@linutronix.de
During early boot the NMI safe timekeeper returns 0 until the first
clocksource becomes available.
This prevents it from being used for printk or other facilities which today
use sched clock. sched clock can be available way before timekeeping is
initialized.
The obvious workaround for this is to utilize the early sched clock in the
default dummy clock read function until a clocksource becomes available.
After switching to the clocksource clock MONOTONIC and BOOTTIME will not
jump because the timekeeping_init() bases clock MONOTONIC on sched clock
and the offset between clock MONOTONIC and BOOTTIME is zero during boot.
Clock REALTIME cannot provide useful timestamps during early boot up to
the point where a persistent clock becomes available, which is either in
timekeeping_init() or later when the RTC driver which might depend on I2C
or other subsystems is initialized.
There is a minor difference to sched_clock() vs. suspend/resume. As the
timekeeper clock source might not be accessible during suspend, after
timekeeping_suspend() timestamps freeze up to the point where
timekeeping_resume() is invoked. OTOH this is true for some sched clock
implementations as well.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200814115512.041422402@linutronix.de
Switch over time namespaces to use the newly introduced common lifetime
counter.
Currently every namespace type has its own lifetime counter which is stored
in the specific namespace struct. The lifetime counters are used
identically for all namespaces types. Namespaces may of course have
additional unrelated counters and these are not altered.
This introduces a common lifetime counter into struct ns_common. The
ns_common struct encompasses information that all namespaces share. That
should include the lifetime counter since its common for all of them.
It also allows us to unify the type of the counters across all namespaces.
Most of them use refcount_t but one uses atomic_t and at least one uses
kref. Especially the last one doesn't make much sense since it's just a
wrapper around refcount_t since 2016 and actually complicates cleanup
operations by having to use container_of() to cast the correct namespace
struct out of struct ns_common.
Having the lifetime counter for the namespaces in one place reduces
maintenance cost. Not just because after switching all namespaces over we
will have removed more code than we added but also because the logic is
more easily understandable and we indicate to the user that the basic
lifetime requirements for all namespaces are currently identical.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/159644982033.604812.9406853013011123238.stgit@localhost.localdomain
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
- Preparatory work to allow S390 to switch over to the generic VDSO
implementation.
S390 requires that the VDSO data pointer is handed in to the counter
read function when time namespace support is enabled. Adding the pointer
is a NOOP for all other architectures because the compiler is supposed
to optimize that out when it is unused in the architecture specific
inline. The change also solved a similar problem for MIPS which
fortunately has time namespaces not yet enabled.
S390 needs to update clock related VDSO data independent of the
timekeeping updates. This was solved so far with yet another sequence
counter in the S390 implementation. A better solution is to utilize the
already existing VDSO sequence count for this. The core code now exposes
helper functions which allow to serialize against the timekeeper code
and against concurrent readers.
S390 needs extra data for their clock readout function. The initial
common VDSO data structure did not provide a way to add that. It now has
an embedded architecture specific struct embedded which defaults to an
empty struct.
Doing this now avoids tree dependencies and conflicts post rc1 and
allows all other architectures which work on generic VDSO support to
work from a common upstream base.
- A trivial comment fix.
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Merge tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timekeeping updates from Thomas Gleixner:
"A set of timekeeping/VDSO updates:
- Preparatory work to allow S390 to switch over to the generic VDSO
implementation.
S390 requires that the VDSO data pointer is handed in to the
counter read function when time namespace support is enabled.
Adding the pointer is a NOOP for all other architectures because
the compiler is supposed to optimize that out when it is unused in
the architecture specific inline. The change also solved a similar
problem for MIPS which fortunately has time namespaces not yet
enabled.
S390 needs to update clock related VDSO data independent of the
timekeeping updates. This was solved so far with yet another
sequence counter in the S390 implementation. A better solution is
to utilize the already existing VDSO sequence count for this. The
core code now exposes helper functions which allow to serialize
against the timekeeper code and against concurrent readers.
S390 needs extra data for their clock readout function. The initial
common VDSO data structure did not provide a way to add that. It
now has an embedded architecture specific struct embedded which
defaults to an empty struct.
Doing this now avoids tree dependencies and conflicts post rc1 and
allows all other architectures which work on generic VDSO support
to work from a common upstream base.
- A trivial comment fix"
* tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
time: Delete repeated words in comments
lib/vdso: Allow to add architecture-specific vdso data
timekeeping/vsyscall: Provide vdso_update_begin/end()
vdso/treewide: Add vdso_data pointer argument to __arch_get_hw_counter()
posix CPU timers into task work context. The tick interrupt is reduced to a
quick check which queues the work which is doing the heavy lifting before
returning to user space or going back to guest mode. Moving this out is
deferring the signal delivery slightly but posix CPU timers are inaccurate
by nature as they depend on the tick so there is no real damage. The
relevant test cases all passed.
This lifts the last offender for RT out of the hard interrupt context tick
handler, but it also has the general benefit that the actual heavy work is
accounted to the task/process and not to the tick interrupt itself.
Further optimizations are possible to break long sighand lock hold and
interrupt disabled (on !RT kernels) times when a massive amount of posix
CPU timers (which are unpriviledged) is armed for a task/process.
This is currently only enabled for x86 because the architecture has to
ensure that task work is handled in KVM before entering a guest, which was
just established for x86 with the new common entry/exit code which got
merged post 5.8 and is not the case for other KVM architectures.
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Merge tag 'timers-core-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull more timer updates from Thomas Gleixner:
"A set of posix CPU timer changes which allows to defer the heavy work
of posix CPU timers into task work context. The tick interrupt is
reduced to a quick check which queues the work which is doing the
heavy lifting before returning to user space or going back to guest
mode. Moving this out is deferring the signal delivery slightly but
posix CPU timers are inaccurate by nature as they depend on the tick
so there is no real damage. The relevant test cases all passed.
This lifts the last offender for RT out of the hard interrupt context
tick handler, but it also has the general benefit that the actual
heavy work is accounted to the task/process and not to the tick
interrupt itself.
Further optimizations are possible to break long sighand lock hold and
interrupt disabled (on !RT kernels) times when a massive amount of
posix CPU timers (which are unpriviledged) is armed for a
task/process.
This is currently only enabled for x86 because the architecture has to
ensure that task work is handled in KVM before entering a guest, which
was just established for x86 with the new common entry/exit code which
got merged post 5.8 and is not the case for other KVM architectures"
* tag 'timers-core-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86: Select POSIX_CPU_TIMERS_TASK_WORK
posix-cpu-timers: Provide mechanisms to defer timer handling to task_work
posix-cpu-timers: Split run_posix_cpu_timers()
- Untangle the header spaghetti which causes build failures in various
situations caused by the lockdep additions to seqcount to validate that
the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict per
CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot
validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored and
write_seqcount_begin() has a lockdep assertion to validate that the
lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API is
unchanged and determines the type at compile time with the help of
_Generic which is possible now that the minimal GCC version has been
moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs which
have been addressed already independent of this.
While generaly useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if the
writers are serialized by an associated lock, which leads to the well
known reader preempts writer livelock. RT prevents this by storing the
associated lock pointer independent of lockdep in the seqcount and
changing the reader side to block on the lock when a reader detects
that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and initializers.
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Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Thomas Gleixner:
"A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in
various situations caused by the lockdep additions to seqcount to
validate that the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict
per CPU seqcounts. As the lock is not part of the seqcount, lockdep
cannot validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored
and write_seqcount_begin() has a lockdep assertion to validate that
the lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API
is unchanged and determines the type at compile time with the help
of _Generic which is possible now that the minimal GCC version has
been moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs
which have been addressed already independent of this.
While generally useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if
the writers are serialized by an associated lock, which leads to
the well known reader preempts writer livelock. RT prevents this by
storing the associated lock pointer independent of lockdep in the
seqcount and changing the reader side to block on the lock when a
reader detects that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and
initializers"
* tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
locking/seqlock, headers: Untangle the spaghetti monster
locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header
x86/headers: Remove APIC headers from <asm/smp.h>
seqcount: More consistent seqprop names
seqcount: Compress SEQCNT_LOCKNAME_ZERO()
seqlock: Fold seqcount_LOCKNAME_init() definition
seqlock: Fold seqcount_LOCKNAME_t definition
seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g
hrtimer: Use sequence counter with associated raw spinlock
kvm/eventfd: Use sequence counter with associated spinlock
userfaultfd: Use sequence counter with associated spinlock
NFSv4: Use sequence counter with associated spinlock
iocost: Use sequence counter with associated spinlock
raid5: Use sequence counter with associated spinlock
vfs: Use sequence counter with associated spinlock
timekeeping: Use sequence counter with associated raw spinlock
xfrm: policy: Use sequence counters with associated lock
netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
netfilter: conntrack: Use sequence counter with associated spinlock
sched: tasks: Use sequence counter with associated spinlock
...
Drop repeated words in kernel/time/. {when, one, into}
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Link: https://lore.kernel.org/r/20200807033248.8452-1-rdunlap@infradead.org
Running posix CPU timers in hard interrupt context has a few downsides:
- For PREEMPT_RT it cannot work as the expiry code needs to take
sighand lock, which is a 'sleeping spinlock' in RT. The original RT
approach of offloading the posix CPU timer handling into a high
priority thread was clumsy and provided no real benefit in general.
- For fine grained accounting it's just wrong to run this in context of
the timer interrupt because that way a process specific CPU time is
accounted to the timer interrupt.
- Long running timer interrupts caused by a large amount of expiring
timers which can be created and armed by unpriviledged user space.
There is no hard requirement to expire them in interrupt context.
If the signal is targeted at the task itself then it won't be delivered
before the task returns to user space anyway. If the signal is targeted at
a supervisor process then it might be slightly delayed, but posix CPU
timers are inaccurate anyway due to the fact that they are tied to the
tick.
Provide infrastructure to schedule task work which allows splitting the
posix CPU timer code into a quick check in interrupt context and a thread
context expiry and signal delivery function. This has to be enabled by
architectures as it requires that the architecture specific KVM
implementation handles pending task work before exiting to guest mode.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200730102337.783470146@linutronix.de
Split it up as a preparatory step to move the heavy lifting out of
interrupt context.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200730102337.677439437@linutronix.de
Architectures can have the requirement to add additional architecture
specific data to the VDSO data page which needs to be updated independent
of the timekeeper updates.
To protect these updates vs. concurrent readers and a conflicting update
through timekeeping, provide helper functions to make such updates safe.
vdso_update_begin() takes the timekeeper_lock to protect against a
potential update from timekeeper code and increments the VDSO sequence
count to signal data inconsistency to concurrent readers. vdso_update_end()
makes the sequence count even again to signal data consistency and drops
the timekeeper lock.
[ Sven: Add interrupt disable handling to the functions ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200804150124.41692-3-svens@linux.ibm.com
- Prevent unnecessary timer softirq invocations by extending the tracking
of the next expiring timer in the timer wheel beyond the existing NOHZ
functionality. The tracking overhead at enqueue time is within the
noise, but on sensitive workloads the avoidance of the soft interrupt
invocation is a measurable improvement.
- The obligatory new clocksource driver for Ingenic X100 OST
- The usual fixes, improvements, cleanups and extensions for newer chip
variants all over the driver space.
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Merge tag 'timers-core-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Time, timers and related driver updates:
- Prevent unnecessary timer softirq invocations by extending the
tracking of the next expiring timer in the timer wheel beyond the
existing NOHZ functionality.
The tracking overhead at enqueue time is within the noise, but on
sensitive workloads the avoidance of the soft interrupt invocation
is a measurable improvement.
- The obligatory new clocksource driver for Ingenic X100 OST
- The usual fixes, improvements, cleanups and extensions for newer
chip variants all over the driver space"
* tag 'timers-core-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (28 commits)
timers: Recalculate next timer interrupt only when necessary
clocksource/drivers/ingenic: Add support for the Ingenic X1000 OST.
dt-bindings: timer: Add Ingenic X1000 OST bindings.
clocksource/drivers: Replace HTTP links with HTTPS ones
clocksource/drivers/nomadik-mtu: Handle 32kHz clock
clocksource/drivers/sh_cmt: Use "kHz" for kilohertz
clocksource/drivers/imx: Add support for i.MX TPM driver with ARM64
clocksource/drivers/ingenic: Add high resolution timer support for SMP/SMT.
timers: Lower base clock forwarding threshold
timers: Remove must_forward_clk
timers: Spare timer softirq until next expiry
timers: Expand clk forward logic beyond nohz
timers: Reuse next expiry cache after nohz exit
timers: Always keep track of next expiry
timers: Optimize _next_timer_interrupt() level iteration
timers: Add comments about calc_index() ceiling work
timers: Move trigger_dyntick_cpu() to enqueue_timer()
timers: Use only bucket expiry for base->next_expiry value
timers: Preserve higher bits of expiration on index calculation
clocksource/drivers/timer-atmel-tcb: Add sama5d2 support
...
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Merge tag 'threads-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull thread updates from Christian Brauner:
"This contains the changes to add the missing support for attaching to
time namespaces via pidfds.
Last cycle setns() was changed to support attaching to multiple
namespaces atomically. This requires all namespaces to have a point of
no return where they can't fail anymore.
Specifically, <namespace-type>_install() is allowed to perform
permission checks and install the namespace into the new struct nsset
that it has been given but it is not allowed to make visible changes
to the affected task. Once <namespace-type>_install() returns,
anything that the given namespace type additionally requires to be
setup needs to ideally be done in a function that can't fail or if it
fails the failure must be non-fatal.
For time namespaces the relevant functions that fell into this
category were timens_set_vvar_page() and vdso_join_timens(). The
latter could still fail although it didn't need to. This function is
only implemented for vdso_join_timens() in current mainline. As
discussed on-list (cf. [1]), in order to make setns() support time
namespaces when attaching to multiple namespaces at once properly we
changed vdso_join_timens() to always succeed. So vdso_join_timens()
replaces the mmap_write_lock_killable() with mmap_read_lock().
Please note that arm is about to grow vdso support for time namespaces
(possibly this merge window). We've synced on this change and arm64
also uses mmap_read_lock(), i.e. makes vdso_join_timens() a function
that can't fail. Once the changes here and the arm64 changes have
landed, vdso_join_timens() should be turned into a void function so
it's obvious to callers and implementers on other architectures that
the expectation is that it can't fail.
We didn't do this right away because it would've introduced
unnecessary merge conflicts between the two trees for no major gain.
As always, tests included"
[1]: https://lore.kernel.org/lkml/20200611110221.pgd3r5qkjrjmfqa2@wittgenstein
* tag 'threads-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
tests: add CLONE_NEWTIME setns tests
nsproxy: support CLONE_NEWTIME with setns()
timens: add timens_commit() helper
timens: make vdso_join_timens() always succeed
- Improve uclamp performance by using a static key for the fast path
- Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
better power efficiency of RT tasks on battery powered devices.
(The default is to maximize performance & reduce RT latencies.)
- Improve utime and stime tracking accuracy, which had a fixed boundary
of error, which created larger and larger relative errors as the values
become larger. This is now replaced with more precise arithmetics,
using the new mul_u64_u64_div_u64() helper in math64.h.
- Improve the deadline scheduler, such as making it capacity aware
- Improve frequency-invariant scheduling
- Misc cleanups in energy/power aware scheduling
- Add sched_update_nr_running tracepoint to track changes to nr_running
- Documentation additions and updates
- Misc cleanups and smaller fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Improve uclamp performance by using a static key for the fast path
- Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
better power efficiency of RT tasks on battery powered devices.
(The default is to maximize performance & reduce RT latencies.)
- Improve utime and stime tracking accuracy, which had a fixed boundary
of error, which created larger and larger relative errors as the
values become larger. This is now replaced with more precise
arithmetics, using the new mul_u64_u64_div_u64() helper in math64.h.
- Improve the deadline scheduler, such as making it capacity aware
- Improve frequency-invariant scheduling
- Misc cleanups in energy/power aware scheduling
- Add sched_update_nr_running tracepoint to track changes to nr_running
- Documentation additions and updates
- Misc cleanups and smaller fixes
* tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
sched/doc: Factorize bits between sched-energy.rst & sched-capacity.rst
sched/doc: Document capacity aware scheduling
sched: Document arch_scale_*_capacity()
arm, arm64: Fix selection of CONFIG_SCHED_THERMAL_PRESSURE
Documentation/sysctl: Document uclamp sysctl knobs
sched/uclamp: Add a new sysctl to control RT default boost value
sched/uclamp: Fix a deadlock when enabling uclamp static key
sched: Remove duplicated tick_nohz_full_enabled() check
sched: Fix a typo in a comment
sched/uclamp: Remove unnecessary mutex_init()
arm, arm64: Select CONFIG_SCHED_THERMAL_PRESSURE
sched: Cleanup SCHED_THERMAL_PRESSURE kconfig entry
arch_topology, sched/core: Cleanup thermal pressure definition
trace/events/sched.h: fix duplicated word
linux/sched/mm.h: drop duplicated words in comments
smp: Fix a potential usage of stale nr_cpus
sched/fair: update_pick_idlest() Select group with lowest group_util when idle_cpus are equal
sched: nohz: stop passing around unused "ticks" parameter.
sched: Better document ttwu()
sched: Add a tracepoint to track rq->nr_running
...
- Removal of the tremendously unpopular read_barrier_depends() barrier,
which is a NOP on all architectures apart from Alpha, in favour of
allowing architectures to override READ_ONCE() and do whatever dance
they need to do to ensure address dependencies provide LOAD ->
LOAD/STORE ordering. This work also offers a potential solution if
compilers are shown to convert LOAD -> LOAD address dependencies into
control dependencies (e.g. under LTO), as weakly ordered architectures
will effectively be able to upgrade READ_ONCE() to smp_load_acquire().
The latter case is not used yet, but will be discussed further at LPC.
- Make the MSI/IOMMU input/output ID translation PCI agnostic, augment
the MSI/IOMMU ACPI/OF ID mapping APIs to accept an input ID
bus-specific parameter and apply the resulting changes to the device
ID space provided by the Freescale FSL bus.
- arm64 support for TLBI range operations and translation table level
hints (part of the ARMv8.4 architecture version).
- Time namespace support for arm64.
- Export the virtual and physical address sizes in vmcoreinfo for
makedumpfile and crash utilities.
- CPU feature handling cleanups and checks for programmer errors
(overlapping bit-fields).
- ACPI updates for arm64: disallow AML accesses to EFI code regions and
kernel memory.
- perf updates for arm64.
- Miscellaneous fixes and cleanups, most notably PLT counting
optimisation for module loading, recordmcount fix to ignore
relocations other than R_AARCH64_CALL26, CMA areas reserved for
gigantic pages on 16K and 64K configurations.
- Trivial typos, duplicate words.
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Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 and cross-arch updates from Catalin Marinas:
"Here's a slightly wider-spread set of updates for 5.9.
Going outside the usual arch/arm64/ area is the removal of
read_barrier_depends() series from Will and the MSI/IOMMU ID
translation series from Lorenzo.
The notable arm64 updates include ARMv8.4 TLBI range operations and
translation level hint, time namespace support, and perf.
Summary:
- Removal of the tremendously unpopular read_barrier_depends()
barrier, which is a NOP on all architectures apart from Alpha, in
favour of allowing architectures to override READ_ONCE() and do
whatever dance they need to do to ensure address dependencies
provide LOAD -> LOAD/STORE ordering.
This work also offers a potential solution if compilers are shown
to convert LOAD -> LOAD address dependencies into control
dependencies (e.g. under LTO), as weakly ordered architectures will
effectively be able to upgrade READ_ONCE() to smp_load_acquire().
The latter case is not used yet, but will be discussed further at
LPC.
- Make the MSI/IOMMU input/output ID translation PCI agnostic,
augment the MSI/IOMMU ACPI/OF ID mapping APIs to accept an input ID
bus-specific parameter and apply the resulting changes to the
device ID space provided by the Freescale FSL bus.
- arm64 support for TLBI range operations and translation table level
hints (part of the ARMv8.4 architecture version).
- Time namespace support for arm64.
- Export the virtual and physical address sizes in vmcoreinfo for
makedumpfile and crash utilities.
- CPU feature handling cleanups and checks for programmer errors
(overlapping bit-fields).
- ACPI updates for arm64: disallow AML accesses to EFI code regions
and kernel memory.
- perf updates for arm64.
- Miscellaneous fixes and cleanups, most notably PLT counting
optimisation for module loading, recordmcount fix to ignore
relocations other than R_AARCH64_CALL26, CMA areas reserved for
gigantic pages on 16K and 64K configurations.
- Trivial typos, duplicate words"
Link: http://lkml.kernel.org/r/20200710165203.31284-1-will@kernel.org
Link: http://lkml.kernel.org/r/20200619082013.13661-1-lorenzo.pieralisi@arm.com
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (82 commits)
arm64: use IRQ_STACK_SIZE instead of THREAD_SIZE for irq stack
arm64/mm: save memory access in check_and_switch_context() fast switch path
arm64: sigcontext.h: delete duplicated word
arm64: ptrace.h: delete duplicated word
arm64: pgtable-hwdef.h: delete duplicated words
bus: fsl-mc: Add ACPI support for fsl-mc
bus/fsl-mc: Refactor the MSI domain creation in the DPRC driver
of/irq: Make of_msi_map_rid() PCI bus agnostic
of/irq: make of_msi_map_get_device_domain() bus agnostic
dt-bindings: arm: fsl: Add msi-map device-tree binding for fsl-mc bus
of/device: Add input id to of_dma_configure()
of/iommu: Make of_map_rid() PCI agnostic
ACPI/IORT: Add an input ID to acpi_dma_configure()
ACPI/IORT: Remove useless PCI bus walk
ACPI/IORT: Make iort_msi_map_rid() PCI agnostic
ACPI/IORT: Make iort_get_device_domain IRQ domain agnostic
ACPI/IORT: Make iort_match_node_callback walk the ACPI namespace for NC
arm64: enable time namespace support
arm64/vdso: Restrict splitting VVAR VMA
arm64/vdso: Handle faults on timens page
...
This modifies the first 32 bits out of the 128 bits of a random CPU's
net_rand_state on interrupt or CPU activity to complicate remote
observations that could lead to guessing the network RNG's internal
state.
Note that depending on some network devices' interrupt rate moderation
or binding, this re-seeding might happen on every packet or even almost
never.
In addition, with NOHZ some CPUs might not even get timer interrupts,
leaving their local state rarely updated, while they are running
networked processes making use of the random state. For this reason, we
also perform this update in update_process_times() in order to at least
update the state when there is user or system activity, since it's the
only case we care about.
Reported-by: Amit Klein <aksecurity@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.
Use the new seqcount_raw_spinlock_t data type, which allows to associate
a raw spinlock with the sequence counter. This enables lockdep to verify
that the raw spinlock used for writer serialization is held when the
write side critical section is entered.
If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-25-a.darwish@linutronix.de
A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.
Use the new seqcount_raw_spinlock_t data type, which allows to associate
a raw spinlock with the sequence counter. This enables lockdep to verify
that the raw spinlock used for writer serialization is held when the
write side critical section is entered.
If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-18-a.darwish@linutronix.de
The nohz tick code recalculates the timer wheel's next expiry on each idle
loop iteration.
On the other hand, the base next expiry is now always cached and updated
upon timer enqueue and execution. Only timer dequeue may leave
base->next_expiry out of date (but then its stale value won't ever go past
the actual next expiry to be recalculated).
Since recalculating the next_expiry isn't a free operation, especially when
the last wheel level is reached to find out that no timer has been enqueued
at all, reuse the next expiry cache when it is known to be reliable, which
it is most of the time.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200723151641.12236-1-frederic@kernel.org
The "ticks" parameter was added in commit 0f004f5a69 ("sched: Cure more
NO_HZ load average woes") since calc_global_nohz() was called and needed
the "ticks" argument.
But in commit c308b56b53 ("sched: Fix nohz load accounting -- again!")
it became unused as the function calc_global_nohz() dropped using "ticks".
Fixes: c308b56b53 ("sched: Fix nohz load accounting -- again!")
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/1593628458-32290-1-git-send-email-paul.gortmaker@windriver.com
sched_clock uses seqcount_t latching to switch between two storage
places protected by the sequence counter. This allows it to have
interruptible, NMI-safe, seqcount_t write side critical sections.
Since 7fc26327b7 ("seqlock: Introduce raw_read_seqcount_latch()"),
raw_read_seqcount_latch() became the standardized way for seqcount_t
latch read paths. Due to the dependent load, it also has one read
memory barrier less than the currently used raw_read_seqcount() API.
Use raw_read_seqcount_latch() for the seqcount_t latch read path.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Link: https://lkml.kernel.org/r/20200625085745.GD117543@hirez.programming.kicks-ass.net
Link: https://lkml.kernel.org/r/20200715092345.GA231464@debian-buster-darwi.lab.linutronix.de
Link: https://lore.kernel.org/r/20200716051130.4359-3-leo.yan@linaro.org
References: 1809bfa44e ("timers, sched/clock: Avoid deadlock during read from NMI")
Signed-off-by: Will Deacon <will@kernel.org>
In order to support perf_event_mmap_page::cap_time features, an
architecture needs, aside from a userspace readable counter register,
to expose the exact clock data so that userspace can convert the
counter register into a correct timestamp.
Provide struct clock_read_data and two (seqcount) helpers so that
architectures (arm64 in specific) can expose the numbers to userspace.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Link: https://lore.kernel.org/r/20200716051130.4359-2-leo.yan@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
There is nothing that prevents from forwarding the base clock if it's one
jiffy off. The reason for this arbitrary limit of two jiffies is historical
and does not longer exist.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-13-frederic@kernel.org
There is no reason to keep this guard around. The code makes sure that
base->clk remains sane and won't be forwarded beyond jiffies nor set
backward.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-12-frederic@kernel.org
Now that the core timer infrastructure doesn't depend anymore on
periodic base->clk increments, even when the CPU is not in NO_HZ mode,
timer softirqs can be skipped until there are timers to expire.
Some spurious softirqs can still remain since base->next_expiry doesn't
keep track of canceled timers but this still reduces the number of softirqs
significantly: ~15 times less for HZ=1000 and ~5 times less for HZ=100.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-11-frederic@kernel.org
As for next_expiry, the base->clk catch up logic will be expanded beyond
NOHZ in order to avoid triggering useless softirqs.
If softirqs should only fire to expire pending timers, periodic base->clk
increments must be skippable for random amounts of time. Therefore prepare
to catch-up with missing updates whenever an up-to-date base clock is
needed.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-10-frederic@kernel.org
Now that the next expiry it tracked unconditionally when a timer is added,
this information can be reused on a tick firing after exiting nohz.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-9-frederic@kernel.org
So far next expiry was only tracked while the CPU was in nohz_idle mode
in order to cope with missing ticks that can't increment the base->clk
periodically anymore.
This logic is going to be expanded beyond nohz in order to spare timer
softirqs so do it unconditionally.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-8-frederic@kernel.org
If a level has a timer that expires before reaching the next level, there
is no need to iterate further.
The next level is reached when the 3 lower bits of the current level are
cleared. If the next event happens before/during that, the next levels
won't provide an earlier expiration.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-7-frederic@kernel.org
calc_index() adds 1 unit of the level granularity to the expiry passed
in parameter to ensure that the timer doesn't expire too early. Add a
comment to explain that and the resulting layout in the wheel.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-6-frederic@kernel.org
Consolidate the code by calling trigger_dyntick_cpu() from
enqueue_timer() instead of calling it from all its callers.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-5-frederic@kernel.org
The bucket expiry time is the effective expriy time of timers and is
greater than or equal to the requested timer expiry time. This is due
to the guarantee that timers never expire early and the reduced expiry
granularity in the secondary wheel levels.
When a timer is enqueued, trigger_dyntick_cpu() checks whether the
timer is the new first timer. This check compares next_expiry with
the requested timer expiry value and not with the effective expiry
value of the bucket into which the timer was queued.
Storing the requested timer expiry value in base->next_expiry can lead
to base->clk going backwards if the requested timer expiry value is
smaller than base->clk. Commit 30c66fc30e ("timer: Prevent base->clk
from moving backward") worked around this by preventing the store when
timer->expiry is before base->clk, but did not fix the underlying
problem.
Use the expiry value of the bucket into which the timer is queued to
do the new first timer check. This fixes the base->clk going backward
problem.
The workaround of commit 30c66fc30e ("timer: Prevent base->clk from
moving backward") in trigger_dyntick_cpu() is not longer necessary as the
timers bucket expiry is guaranteed to be greater than or equal base->clk.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200717140551.29076-4-frederic@kernel.org
The higher bits of the timer expiration are cropped while calling
calc_index() due to the implicit cast from unsigned long to unsigned int.
This loss shouldn't have consequences on the current code since all the
computation to calculate the index is done on the lower 32 bits.
However to prepare for returning the actual bucket expiration from
calc_index() in order to properly fix base->next_expiry updates, the higher
bits need to be preserved.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200717140551.29076-3-frederic@kernel.org
When an expiration delta falls into the last level of the wheel, that delta
has be compared against the maximum possible delay and reduced to fit in if
necessary.
However instead of comparing the delta against the maximum, the code
compares the actual expiry against the maximum. Then instead of fixing the
delta to fit in, it sets the maximum delta as the expiry value.
This can result in various undesired outcomes, the worst possible one
being a timer expiring 15 days ahead to fire immediately.
Fixes: 500462a9de ("timers: Switch to a non-cascading wheel")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200717140551.29076-2-frederic@kernel.org
When a timer is enqueued with a negative delta (ie: expiry is below
base->clk), it gets added to the wheel as expiring now (base->clk).
Yet the value that gets stored in base->next_expiry, while calling
trigger_dyntick_cpu(), is the initial timer->expires value. The
resulting state becomes:
base->next_expiry < base->clk
On the next timer enqueue, forward_timer_base() may accidentally
rewind base->clk. As a possible outcome, timers may expire way too
early, the worst case being that the highest wheel levels get spuriously
processed again.
To prevent from that, make sure that base->next_expiry doesn't get below
base->clk.
Fixes: a683f390b9 ("timers: Forward the wheel clock whenever possible")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200703010657.2302-1-frederic@kernel.org
So far setns() was missing time namespace support. This was partially due
to it simply not being implemented but also because vdso_join_timens()
could still fail which made switching to multiple namespaces atomically
problematic. This is now fixed so support CLONE_NEWTIME with setns()
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Andrei Vagin <avagin@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200706154912.3248030-4-christian.brauner@ubuntu.com
