Commit graph

362 commits

Author SHA1 Message Date
Linus Torvalds
3fe2f7446f Changes in this cycle were:
- Cleanups for SCHED_DEADLINE
  - Tracing updates/fixes
  - CPU Accounting fixes
  - First wave of changes to optimize the overhead of the scheduler build,
    from the fast-headers tree - including placeholder *_api.h headers for
    later header split-ups.
  - Preempt-dynamic using static_branch() for ARM64
  - Isolation housekeeping mask rework; preperatory for further changes
  - NUMA-balancing: deal with CPU-less nodes
  - NUMA-balancing: tune systems that have multiple LLC cache domains per node (eg. AMD)
  - Updates to RSEQ UAPI in preparation for glibc usage
  - Lots of RSEQ/selftests, for same
  - Add Suren as PSI co-maintainer
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2022-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Cleanups for SCHED_DEADLINE

 - Tracing updates/fixes

 - CPU Accounting fixes

 - First wave of changes to optimize the overhead of the scheduler
   build, from the fast-headers tree - including placeholder *_api.h
   headers for later header split-ups.

 - Preempt-dynamic using static_branch() for ARM64

 - Isolation housekeeping mask rework; preperatory for further changes

 - NUMA-balancing: deal with CPU-less nodes

 - NUMA-balancing: tune systems that have multiple LLC cache domains per
   node (eg. AMD)

 - Updates to RSEQ UAPI in preparation for glibc usage

 - Lots of RSEQ/selftests, for same

 - Add Suren as PSI co-maintainer

* tag 'sched-core-2022-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (81 commits)
  sched/headers: ARM needs asm/paravirt_api_clock.h too
  sched/numa: Fix boot crash on arm64 systems
  headers/prep: Fix header to build standalone: <linux/psi.h>
  sched/headers: Only include <linux/entry-common.h> when CONFIG_GENERIC_ENTRY=y
  cgroup: Fix suspicious rcu_dereference_check() usage warning
  sched/preempt: Tell about PREEMPT_DYNAMIC on kernel headers
  sched/topology: Remove redundant variable and fix incorrect type in build_sched_domains
  sched/deadline,rt: Remove unused parameter from pick_next_[rt|dl]_entity()
  sched/deadline,rt: Remove unused functions for !CONFIG_SMP
  sched/deadline: Use __node_2_[pdl|dle]() and rb_first_cached() consistently
  sched/deadline: Merge dl_task_can_attach() and dl_cpu_busy()
  sched/deadline: Move bandwidth mgmt and reclaim functions into sched class source file
  sched/deadline: Remove unused def_dl_bandwidth
  sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE
  sched/tracing: Don't re-read p->state when emitting sched_switch event
  sched/rt: Plug rt_mutex_setprio() vs push_rt_task() race
  sched/cpuacct: Remove redundant RCU read lock
  sched/cpuacct: Optimize away RCU read lock
  sched/cpuacct: Fix charge percpu cpuusage
  sched/headers: Reorganize, clean up and optimize kernel/sched/sched.h dependencies
  ...
2022-03-22 14:39:12 -07:00
Jason A. Donenfeld
3191dd5a11 random: clear fast pool, crng, and batches in cpuhp bring up
For the irq randomness fast pool, rather than having to use expensive
atomics, which were visibly the most expensive thing in the entire irq
handler, simply take care of the extreme edge case of resetting count to
zero in the cpuhp online handler, just after workqueues have been
reenabled. This simplifies the code a bit and lets us use vanilla
variables rather than atomics, and performance should be improved.

As well, very early on when the CPU comes up, while interrupts are still
disabled, we clear out the per-cpu crng and its batches, so that it
always starts with fresh randomness.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Sultan Alsawaf <sultan@kerneltoast.com>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2022-02-21 21:14:21 +01:00
Frederic Weisbecker
04d4e665a6 sched/isolation: Use single feature type while referring to housekeeping cpumask
Refer to housekeeping APIs using single feature types instead of flags.
This prevents from passing multiple isolation features at once to
housekeeping interfaces, which soon won't be possible anymore as each
isolation features will have their own cpumask.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20220207155910.527133-5-frederic@kernel.org
2022-02-16 15:57:55 +01:00
Mark Rutland
dce1ca0525 sched/scs: Reset task stack state in bringup_cpu()
To hot unplug a CPU, the idle task on that CPU calls a few layers of C
code before finally leaving the kernel. When KASAN is in use, poisoned
shadow is left around for each of the active stack frames, and when
shadow call stacks are in use. When shadow call stacks (SCS) are in use
the task's saved SCS SP is left pointing at an arbitrary point within
the task's shadow call stack.

When a CPU is offlined than onlined back into the kernel, this stale
state can adversely affect execution. Stale KASAN shadow can alias new
stackframes and result in bogus KASAN warnings. A stale SCS SP is
effectively a memory leak, and prevents a portion of the shadow call
stack being used. Across a number of hotplug cycles the idle task's
entire shadow call stack can become unusable.

We previously fixed the KASAN issue in commit:

  e1b77c9298 ("sched/kasan: remove stale KASAN poison after hotplug")

... by removing any stale KASAN stack poison immediately prior to
onlining a CPU.

Subsequently in commit:

  f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")

... the refactoring left the KASAN and SCS cleanup in one-time idle
thread initialization code rather than something invoked prior to each
CPU being onlined, breaking both as above.

We fixed SCS (but not KASAN) in commit:

  63acd42c0d ("sched/scs: Reset the shadow stack when idle_task_exit")

... but as this runs in the context of the idle task being offlined it's
potentially fragile.

To fix these consistently and more robustly, reset the SCS SP and KASAN
shadow of a CPU's idle task immediately before we online that CPU in
bringup_cpu(). This ensures the idle task always has a consistent state
when it is running, and removes the need to so so when exiting an idle
task.

Whenever any thread is created, dup_task_struct() will give the task a
stack which is free of KASAN shadow, and initialize the task's SCS SP,
so there's no need to specially initialize either for idle thread within
init_idle(), as this was only necessary to handle hotplug cycles.

I've tested this on arm64 with:

* gcc 11.1.0, defconfig +KASAN_INLINE, KASAN_STACK
* clang 12.0.0, defconfig +KASAN_INLINE, KASAN_STACK, SHADOW_CALL_STACK

... offlining and onlining CPUS with:

| while true; do
|   for C in /sys/devices/system/cpu/cpu*/online; do
|     echo 0 > $C;
|     echo 1 > $C;
|   done
| done

Fixes: f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Qian Cai <quic_qiancai@quicinc.com>
Link: https://lore.kernel.org/lkml/20211115113310.35693-1-mark.rutland@arm.com/
2021-11-24 12:20:27 +01:00
Dongli Zhang
ebca71a8c9 cpu/hotplug: Add debug printks for hotplug callback failures
CPU hotplug callbacks can fail and cause a rollback to the previous
state. These failures are silent and therefore hard to debug.

Add pr_debug() to the up and down paths which provide information about the
error code, the CPU and the failed state. The debug printks can be enabled
via kernel command line or sysfs.

[ tglx: Adopt to current mainline, massage printk and changelog ]

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Link: https://lore.kernel.org/r/20210409055316.1709-1-dongli.zhang@oracle.com
2021-08-10 18:31:32 +02:00
YueHaibing
1782dc87b2 cpu/hotplug: Use DEVICE_ATTR_*() macro
Use DEVICE_ATTR_*() helper 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/20210527141105.2312-1-yuehaibing@huawei.com
2021-08-10 18:11:12 +02:00
Randy Dunlap
11bc021d1f cpu/hotplug: Eliminate all kernel-doc warnings
kernel/cpu.c:57: warning: cannot understand function prototype: 'struct cpuhp_cpu_state '
kernel/cpu.c:115: warning: cannot understand function prototype: 'struct cpuhp_step '
kernel/cpu.c:146: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
kernel/cpu.c:75: warning: Function parameter or member 'fail' not described in 'cpuhp_cpu_state'
kernel/cpu.c:75: warning: Function parameter or member 'cpu' not described in 'cpuhp_cpu_state'
kernel/cpu.c:75: warning: Function parameter or member 'node' not described in 'cpuhp_cpu_state'
kernel/cpu.c:75: warning: Function parameter or member 'last' not described in 'cpuhp_cpu_state'
kernel/cpu.c:130: warning: Function parameter or member 'list' not described in 'cpuhp_step'
kernel/cpu.c:130: warning: Function parameter or member 'multi_instance' not described in 'cpuhp_step'
kernel/cpu.c:158: warning: No description found for return value of 'cpuhp_invoke_callback'
kernel/cpu.c:1188: warning: No description found for return value of 'cpu_device_down'
kernel/cpu.c:1400: warning: No description found for return value of 'cpu_device_up'
kernel/cpu.c:1425: warning: No description found for return value of 'bringup_hibernate_cpu'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210809223825.24512-1-rdunlap@infradead.org
2021-08-10 18:07:38 +02:00
Baokun Li
ed3cd1da67 cpu/hotplug: Fix kernel doc warnings for __cpuhp_setup_state_cpuslocked()
Fixes the following W=1 kernel build warning(s):

 kernel/cpu.c:1949: warning: Function parameter or member 
  'name' not described in '__cpuhp_setup_state_cpuslocked'

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210605063003.681049-1-libaokun1@huawei.com
2021-08-10 18:07:38 +02:00
Linus Torvalds
62180152e0 A fix for the CPU hotplug and cpusets interaction:
cpusets delegate the hotplug work to a workqueue to prevent a lock order
 inversion vs. the CPU hotplug lock. The work is not flushed before the
 hotplug operation returns which creates user visible inconsistent state.
 Prevent this by flushing the work after dropping CPU hotplug lock and
 before releasing the outer mutex which serializes the CPU hotplug related
 sysfs interface operations.
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Merge tag 'smp-urgent-2021-06-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull CPU hotplug fix from Thomas Gleixner:
 "A fix for the CPU hotplug and cpusets interaction:

  cpusets delegate the hotplug work to a workqueue to prevent a lock
  order inversion vs. the CPU hotplug lock. The work is not flushed
  before the hotplug operation returns which creates user visible
  inconsistent state. Prevent this by flushing the work after dropping
  CPU hotplug lock and before releasing the outer mutex which serializes
  the CPU hotplug related sysfs interface operations"

* tag 'smp-urgent-2021-06-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpu/hotplug: Cure the cpusets trainwreck
2021-06-29 12:23:02 -07:00
Thomas Gleixner
b22afcdf04 cpu/hotplug: Cure the cpusets trainwreck
Alexey and Joshua tried to solve a cpusets related hotplug problem which is
user space visible and results in unexpected behaviour for some time after
a CPU has been plugged in and the corresponding uevent was delivered.

cpusets delegate the hotplug work (rebuilding cpumasks etc.) to a
workqueue. This is done because the cpusets code has already a lock
nesting of cgroups_mutex -> cpu_hotplug_lock. A synchronous callback or
waiting for the work to finish with cpu_hotplug_lock held can and will
deadlock because that results in the reverse lock order.

As a consequence the uevent can be delivered before cpusets have consistent
state which means that a user space invocation of sched_setaffinity() to
move a task to the plugged CPU fails up to the point where the scheduled
work has been processed.

The same is true for CPU unplug, but that does not create user observable
failure (yet).

It's still inconsistent to claim that an operation is finished before it
actually is and that's the real issue at hand. uevents just make it
reliably observable.

Obviously the problem should be fixed in cpusets/cgroups, but untangling
that is pretty much impossible because according to the changelog of the
commit which introduced this 8 years ago:

 3a5a6d0c2b03("cpuset: don't nest cgroup_mutex inside get_online_cpus()")

the lock order cgroups_mutex -> cpu_hotplug_lock is a design decision and
the whole code is built around that.

So bite the bullet and invoke the relevant cpuset function, which waits for
the work to finish, in _cpu_up/down() after dropping cpu_hotplug_lock and
only when tasks are not frozen by suspend/hibernate because that would
obviously wait forever.

Waiting there with cpu_add_remove_lock, which is protecting the present
and possible CPU maps, held is not a problem at all because neither work
queues nor cpusets/cgroups have any lockchains related to that lock.

Waiting in the hotplug machinery is not problematic either because there
are already state callbacks which wait for hardware queues to drain. It
makes the operations slightly slower, but hotplug is slow anyway.

This ensures that state is consistent before returning from a hotplug
up/down operation. It's still inconsistent during the operation, but that's
a different story.

Add a large comment which explains why this is done and why this is not a
dump ground for the hack of the day to work around half thought out locking
schemes. Document also the implications vs. hotplug operations and
serialization or the lack of it.

Thanks to Alexy and Joshua for analyzing why this temporary
sched_setaffinity() failure happened.

Fixes: 3a5a6d0c2b03("cpuset: don't nest cgroup_mutex inside get_online_cpus()")
Reported-by: Alexey Klimov <aklimov@redhat.com>
Reported-by: Joshua Baker <jobaker@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Alexey Klimov <aklimov@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/87tuowcnv3.ffs@nanos.tec.linutronix.de
2021-06-21 10:31:06 +02:00
Yuan ZhaoXiong
130708331b cpu/hotplug: Simplify access to percpu cpuhp_state
It is unnecessary to invoke per_cpu_ptr() everytime to access cpuhp_state.
Use the available pointer instead.

Signed-off-by: Yuan ZhaoXiong <yuanzhaoxiong@baidu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/1621776690-13264-1-git-send-email-yuanzhaoxiong@baidu.com
2021-05-25 17:24:52 +02:00
Peter Zijlstra
2ea46c6fc9 cpumask/hotplug: Fix cpu_dying() state tracking
Vincent reported that for states with a NULL startup/teardown function
we do not call cpuhp_invoke_callback() (because there is none) and as
such we'll not update the cpu_dying() state.

The stale cpu_dying() can eventually lead to triggering BUG().

Rectify this by updating cpu_dying() in the exact same places the
hotplug machinery tracks its directional state, namely
cpuhp_set_state() and cpuhp_reset_state().

Reported-by: Vincent Donnefort <vincent.donnefort@arm.com>
Suggested-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Donnefort <vincent.donnefort@arm.com>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/YH7r+AoQEReSvxBI@hirez.programming.kicks-ass.net
2021-04-21 13:55:43 +02:00
Peter Zijlstra
e40f74c535 cpumask: Introduce DYING mask
Introduce a cpumask that indicates (for each CPU) what direction the
CPU hotplug is currently going. Notably, it tracks rollbacks. Eg. when
an up fails and we do a roll-back down, it will accurately reflect the
direction.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210310150109.151441252@infradead.org
2021-04-16 17:06:32 +02:00
Vincent Donnefort
453e410851 cpu/hotplug: Add cpuhp_invoke_callback_range()
Factorizing and unifying cpuhp callback range invocations, especially for
the hotunplug path, where two different ways of decrementing were used. The
first one, decrements before the callback is called:

 cpuhp_thread_fun()
     state = st->state;
     st->state--;
     cpuhp_invoke_callback(state);

The second one, after:

 take_down_cpu()|cpuhp_down_callbacks()
     cpuhp_invoke_callback(st->state);
     st->state--;

This is problematic for rolling back the steps in case of error, as
depending on the decrement, the rollback will start from N or N-1. It also
makes tracing inconsistent, between steps run in the cpuhp thread and
the others.

Additionally, avoid useless cpuhp_thread_fun() loops by skipping empty
steps.

Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210216103506.416286-4-vincent.donnefort@arm.com
2021-03-06 12:40:22 +01:00
Vincent Donnefort
62f2506940 cpu/hotplug: CPUHP_BRINGUP_CPU failure exception
The atomic states (between CPUHP_AP_IDLE_DEAD and CPUHP_AP_ONLINE) are
triggered by the CPUHP_BRINGUP_CPU step. If the latter fails, no atomic
state can be rolled back.

DEAD callbacks too can't fail and disallow recovery. As a consequence,
during hotunplug, the fail injection interface should prohibit all states
from CPUHP_BRINGUP_CPU to CPUHP_ONLINE.

Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210216103506.416286-3-vincent.donnefort@arm.com
2021-03-06 12:40:22 +01:00
Vincent Donnefort
3ae70c251f cpu/hotplug: Allowing to reset fail injection
Currently, the only way of resetting the fail injection is to trigger a
hotplug, hotunplug or both. This is rather annoying for testing
and, as the default value for this file is -1, it seems pretty natural to
let a user write it.

Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210216103506.416286-2-vincent.donnefort@arm.com
2021-03-06 12:40:22 +01:00
Frederic Weisbecker
43759fe5a1 cpu/hotplug: Add lockdep_is_cpus_held()
This commit adds a lockdep_is_cpus_held() function to verify that the
proper locks are held and that various operations are running in the
correct context.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
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>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-06 16:24:59 -08:00
Linus Torvalds
adb35e8dc9 Scheduler updates:
- 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
  ...
2020-12-14 18:29:11 -08:00
Nicholas Piggin
8ff00399b1 kernel/cpu: add arch override for clear_tasks_mm_cpumask() mm handling
powerpc/64s keeps a counter in the mm which counts bits set in
mm_cpumask as well as other things. This means it can't use generic code
to clear bits out of the mask and doesn't adjust the arch specific
counter.

Add an arch override that allows powerpc/64s to use
clear_tasks_mm_cpumask().

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201126102530.691335-4-npiggin@gmail.com
2020-11-27 00:10:39 +11:00
Thomas Gleixner
1cf12e08bc sched/hotplug: Consolidate task migration on CPU unplug
With the new mechanism which kicks tasks off the outgoing CPU at the end of
schedule() the situation on an outgoing CPU right before the stopper thread
brings it down completely is:

 - All user tasks and all unbound kernel threads have either been migrated
   away or are not running and the next wakeup will move them to a online CPU.

 - All per CPU kernel threads, except cpu hotplug thread and the stopper
   thread have either been unbound or parked by the responsible CPU hotplug
   callback.

That means that at the last step before the stopper thread is invoked the
cpu hotplug thread is the last legitimate running task on the outgoing
CPU.

Add a final wait step right before the stopper thread is kicked which
ensures that any still running tasks on the way to park or on the way to
kick themself of the CPU are either sleeping or gone.

This allows to remove the migrate_tasks() crutch in sched_cpu_dying(). If
sched_cpu_dying() detects that there is still another running task aside of
the stopper thread then it will explode with the appropriate fireworks.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Link: https://lkml.kernel.org/r/20201023102346.547163969@infradead.org
2020-11-10 18:38:58 +01:00
Linus Torvalds
d479c5a191 The changes in this cycle are:
- Optimize the task wakeup CPU selection logic, to improve scalability and
    reduce wakeup latency spikes
 
  - PELT enhancements
 
  - CFS bandwidth handling fixes
 
  - Optimize the wakeup path by remove rq->wake_list and replacing it with ->ttwu_pending
 
  - Optimize IPI cross-calls by making flush_smp_call_function_queue()
    process sync callbacks first.
 
  - Misc fixes and enhancements.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2020-06-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:
 "The changes in this cycle are:

   - Optimize the task wakeup CPU selection logic, to improve
     scalability and reduce wakeup latency spikes

   - PELT enhancements

   - CFS bandwidth handling fixes

   - Optimize the wakeup path by remove rq->wake_list and replacing it
     with ->ttwu_pending

   - Optimize IPI cross-calls by making flush_smp_call_function_queue()
     process sync callbacks first.

   - Misc fixes and enhancements"

* tag 'sched-core-2020-06-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
  irq_work: Define irq_work_single() on !CONFIG_IRQ_WORK too
  sched/headers: Split out open-coded prototypes into kernel/sched/smp.h
  sched: Replace rq::wake_list
  sched: Add rq::ttwu_pending
  irq_work, smp: Allow irq_work on call_single_queue
  smp: Optimize send_call_function_single_ipi()
  smp: Move irq_work_run() out of flush_smp_call_function_queue()
  smp: Optimize flush_smp_call_function_queue()
  sched: Fix smp_call_function_single_async() usage for ILB
  sched/core: Offload wakee task activation if it the wakee is descheduling
  sched/core: Optimize ttwu() spinning on p->on_cpu
  sched: Defend cfs and rt bandwidth quota against overflow
  sched/cpuacct: Fix charge cpuacct.usage_sys
  sched/fair: Replace zero-length array with flexible-array
  sched/pelt: Sync util/runnable_sum with PELT window when propagating
  sched/cpuacct: Use __this_cpu_add() instead of this_cpu_ptr()
  sched/fair: Optimize enqueue_task_fair()
  sched: Make scheduler_ipi inline
  sched: Clean up scheduler_ipi()
  sched/core: Simplify sched_init()
  ...
2020-06-03 13:06:42 -07:00
Qais Yousef
fb7fb84a0c cpu/hotplug: Remove __freeze_secondary_cpus()
The refactored function is no longer required as the codepaths that call
freeze_secondary_cpus() are all suspend/resume related now.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Link: https://lkml.kernel.org/r/20200430114004.17477-2-qais.yousef@arm.com
2020-05-07 15:18:41 +02:00
Qais Yousef
5655585589 cpu/hotplug: Remove disable_nonboot_cpus()
The single user could have called freeze_secondary_cpus() directly.

Since this function was a source of confusion, remove it as it's
just a pointless wrapper.

While at it, rename enable_nonboot_cpus() to thaw_secondary_cpus() to
preserve the naming symmetry.

Done automatically via:

	git grep -l enable_nonboot_cpus | xargs sed -i 's/enable_nonboot_cpus/thaw_secondary_cpus/g'

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Link: https://lkml.kernel.org/r/20200430114004.17477-1-qais.yousef@arm.com
2020-05-07 15:18:40 +02:00
Peter Zijlstra
bf2c59fce4 sched/core: Fix illegal RCU from offline CPUs
In the CPU-offline process, it calls mmdrop() after idle entry and the
subsequent call to cpuhp_report_idle_dead(). Once execution passes the
call to rcu_report_dead(), RCU is ignoring the CPU, which results in
lockdep complaining when mmdrop() uses RCU from either memcg or
debugobjects below.

Fix it by cleaning up the active_mm state from BP instead. Every arch
which has CONFIG_HOTPLUG_CPU should have already called idle_task_exit()
from AP. The only exception is parisc because it switches them to
&init_mm unconditionally (see smp_boot_one_cpu() and smp_cpu_init()),
but the patch will still work there because it calls mmgrab(&init_mm) in
smp_cpu_init() and then should call mmdrop(&init_mm) in finish_cpu().

  WARNING: suspicious RCU usage
  -----------------------------
  kernel/workqueue.c:710 RCU or wq_pool_mutex should be held!

  other info that might help us debug this:

  RCU used illegally from offline CPU!
  Call Trace:
   dump_stack+0xf4/0x164 (unreliable)
   lockdep_rcu_suspicious+0x140/0x164
   get_work_pool+0x110/0x150
   __queue_work+0x1bc/0xca0
   queue_work_on+0x114/0x120
   css_release+0x9c/0xc0
   percpu_ref_put_many+0x204/0x230
   free_pcp_prepare+0x264/0x570
   free_unref_page+0x38/0xf0
   __mmdrop+0x21c/0x2c0
   idle_task_exit+0x170/0x1b0
   pnv_smp_cpu_kill_self+0x38/0x2e0
   cpu_die+0x48/0x64
   arch_cpu_idle_dead+0x30/0x50
   do_idle+0x2f4/0x470
   cpu_startup_entry+0x38/0x40
   start_secondary+0x7a8/0xa80
   start_secondary_resume+0x10/0x14

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Link: https://lkml.kernel.org/r/20200401214033.8448-1-cai@lca.pw
2020-04-30 20:14:41 +02:00
Ethon Paul
182e073f68 cpu/hotplug: Fix a typo in comment "broadacasted"->"broadcasted"
Signed-off-by: Ethon Paul <ethp@qq.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200417164008.6541-1-ethp@qq.com
2020-04-27 22:42:04 +02:00
Linus Torvalds
992a1a3b45 CPU (hotplug) updates:
- Support for locked CSD objects in smp_call_function_single_async()
     which allows to simplify callsites in the scheduler core and MIPS
 
   - Treewide consolidation of CPU hotplug functions which ensures the
     consistency between the sysfs interface and kernel state. The low level
     functions cpu_up/down() are now confined to the core code and not
     longer accessible from random code.
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Merge tag 'smp-core-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core SMP updates from Thomas Gleixner:
 "CPU (hotplug) updates:

   - Support for locked CSD objects in smp_call_function_single_async()
     which allows to simplify callsites in the scheduler core and MIPS

   - Treewide consolidation of CPU hotplug functions which ensures the
     consistency between the sysfs interface and kernel state. The low
     level functions cpu_up/down() are now confined to the core code and
     not longer accessible from random code"

* tag 'smp-core-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
  cpu/hotplug: Ignore pm_wakeup_pending() for disable_nonboot_cpus()
  cpu/hotplug: Hide cpu_up/down()
  cpu/hotplug: Move bringup of secondary CPUs out of smp_init()
  torture: Replace cpu_up/down() with add/remove_cpu()
  firmware: psci: Replace cpu_up/down() with add/remove_cpu()
  xen/cpuhotplug: Replace cpu_up/down() with device_online/offline()
  parisc: Replace cpu_up/down() with add/remove_cpu()
  sparc: Replace cpu_up/down() with add/remove_cpu()
  powerpc: Replace cpu_up/down() with add/remove_cpu()
  x86/smp: Replace cpu_up/down() with add/remove_cpu()
  arm64: hibernate: Use bringup_hibernate_cpu()
  cpu/hotplug: Provide bringup_hibernate_cpu()
  arm64: Use reboot_cpu instead of hardconding it to 0
  arm64: Don't use disable_nonboot_cpus()
  ARM: Use reboot_cpu instead of hardcoding it to 0
  ARM: Don't use disable_nonboot_cpus()
  ia64: Replace cpu_down() with smp_shutdown_nonboot_cpus()
  cpu/hotplug: Create a new function to shutdown nonboot cpus
  cpu/hotplug: Add new {add,remove}_cpu() functions
  sched/core: Remove rq.hrtick_csd_pending
  ...
2020-03-30 18:06:39 -07:00
Thomas Gleixner
e98eac6ff1 cpu/hotplug: Ignore pm_wakeup_pending() for disable_nonboot_cpus()
A recent change to freeze_secondary_cpus() which added an early abort if a
wakeup is pending missed the fact that the function is also invoked for
shutdown, reboot and kexec via disable_nonboot_cpus().

In case of disable_nonboot_cpus() the wakeup event needs to be ignored as
the purpose is to terminate the currently running kernel.

Add a 'suspend' argument which is only set when the freeze is in context of
a suspend operation. If not set then an eventually pending wakeup event is
ignored.

Fixes: a66d955e91 ("cpu/hotplug: Abort disabling secondary CPUs if wakeup is pending")
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Pavankumar Kondeti <pkondeti@codeaurora.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/874kuaxdiz.fsf@nanos.tec.linutronix.de
2020-03-28 11:42:55 +01:00
Qais Yousef
33c3736ec8 cpu/hotplug: Hide cpu_up/down()
Use separate functions for the device core to bring a CPU up and down.

Users outside the device core must use add/remove_cpu() which will take
care of extra housekeeping work like keeping sysfs in sync.

Make cpu_up/down() static and replace the extra layer of indirection.

[ tglx: Removed the extra wrapper functions and adjusted function names ]

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200323135110.30522-18-qais.yousef@arm.com
2020-03-25 12:59:38 +01:00
Qais Yousef
b99a26593b cpu/hotplug: Move bringup of secondary CPUs out of smp_init()
This is the last direct user of cpu_up() before it can become an internal
implementation detail of the cpu subsystem.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200323135110.30522-17-qais.yousef@arm.com
2020-03-25 12:59:37 +01:00
Qais Yousef
d720f98604 cpu/hotplug: Provide bringup_hibernate_cpu()
arm64 uses cpu_up() in the resume from hibernation code to ensure that the
CPU on which the system hibernated is online. Provide a core function for
this.

[ tglx: Split out from the combo arm64 patch ]

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20200323135110.30522-9-qais.yousef@arm.com
2020-03-25 12:59:34 +01:00
Qais Yousef
0441a5597c cpu/hotplug: Create a new function to shutdown nonboot cpus
This function will be used later in machine_shutdown() for some
architectures.

disable_nonboot_cpus() is not safe to use when doing machine_down(),
because it relies on freeze_secondary_cpus() which in turn is a
suspend/resume related freeze and could abort if the logic detects any
pending activities that can prevent finishing the offlining process.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200323135110.30522-3-qais.yousef@arm.com
2020-03-25 12:59:31 +01:00
Qais Yousef
93ef1429e5 cpu/hotplug: Add new {add,remove}_cpu() functions
The new functions use device_{online,offline}() which are userspace safe.

This is in preparation to move cpu_{up, down} kernel users to use a safer
interface that is not racy with userspace.

Suggested-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lkml.kernel.org/r/20200323135110.30522-2-qais.yousef@arm.com
2020-03-25 12:59:31 +01:00
Peter Zijlstra
1751060e25 locking/percpu-rwsem, lockdep: Make percpu-rwsem use its own lockdep_map
As preparation for replacing the embedded rwsem, give percpu-rwsem its
own lockdep_map.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200131151539.927625541@infradead.org
2020-02-11 13:10:53 +01:00
Linus Torvalds
c677124e63 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
 "These were the main changes in this cycle:

   - More -rt motivated separation of CONFIG_PREEMPT and
     CONFIG_PREEMPTION.

   - Add more low level scheduling topology sanity checks and warnings
     to filter out nonsensical topologies that break scheduling.

   - Extend uclamp constraints to influence wakeup CPU placement

   - Make the RT scheduler more aware of asymmetric topologies and CPU
     capacities, via uclamp metrics, if CONFIG_UCLAMP_TASK=y

   - Make idle CPU selection more consistent

   - Various fixes, smaller cleanups, updates and enhancements - please
     see the git log for details"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (58 commits)
  sched/fair: Define sched_idle_cpu() only for SMP configurations
  sched/topology: Assert non-NUMA topology masks don't (partially) overlap
  idle: fix spelling mistake "iterrupts" -> "interrupts"
  sched/fair: Remove redundant call to cpufreq_update_util()
  sched/psi: create /proc/pressure and /proc/pressure/{io|memory|cpu} only when psi enabled
  sched/fair: Fix sgc->{min,max}_capacity calculation for SD_OVERLAP
  sched/fair: calculate delta runnable load only when it's needed
  sched/cputime: move rq parameter in irqtime_account_process_tick
  stop_machine: Make stop_cpus() static
  sched/debug: Reset watchdog on all CPUs while processing sysrq-t
  sched/core: Fix size of rq::uclamp initialization
  sched/uclamp: Fix a bug in propagating uclamp value in new cgroups
  sched/fair: Load balance aggressively for SCHED_IDLE CPUs
  sched/fair : Improve update_sd_pick_busiest for spare capacity case
  watchdog: Remove soft_lockup_hrtimer_cnt and related code
  sched/rt: Make RT capacity-aware
  sched/fair: Make EAS wakeup placement consider uclamp restrictions
  sched/fair: Make task_fits_capacity() consider uclamp restrictions
  sched/uclamp: Rename uclamp_util_with() into uclamp_rq_util_with()
  sched/uclamp: Make uclamp util helpers use and return UL values
  ...
2020-01-28 10:07:09 -08:00
Arnd Bergmann
dc8d37ed30 cpu/SMT: Fix x86 link error without CONFIG_SYSFS
When CONFIG_SYSFS is disabled, but CONFIG_HOTPLUG_SMT is enabled,
the kernel fails to link:

arch/x86/power/cpu.o: In function `hibernate_resume_nonboot_cpu_disable':
(.text+0x38d): undefined reference to `cpuhp_smt_enable'
arch/x86/power/hibernate.o: In function `arch_resume_nosmt':
hibernate.c:(.text+0x291): undefined reference to `cpuhp_smt_enable'
hibernate.c:(.text+0x29c): undefined reference to `cpuhp_smt_disable'

Move the exported functions out of the #ifdef section into its
own with the correct conditions.

The patch that caused this is marked for stable backports, so
this one may need to be backported as well.

Fixes: ec527c3180 ("x86/power: Fix 'nosmt' vs hibernation triple fault during resume")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jiri Kosina <jkosina@suse.cz>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20191210195614.786555-1-arnd@arndb.de
2020-01-09 17:31:45 +01:00
Peter Zijlstra
45178ac0ce cpu/hotplug, stop_machine: Fix stop_machine vs hotplug order
Paul reported a very sporadic, rcutorture induced, workqueue failure.
When the planets align, the workqueue rescuer's self-migrate fails and
then triggers a WARN for running a work on the wrong CPU.

Tejun then figured that set_cpus_allowed_ptr()'s stop_one_cpu() call
could be ignored! When stopper->enabled is false, stop_machine will
insta complete the work, without actually doing the work. Worse, it
will not WARN about this (we really should fix this).

It turns out there is a small window where a freshly online'ed CPU is
marked 'online' but doesn't yet have the stopper task running:

	BP				AP

	bringup_cpu()
	  __cpu_up(cpu, idle)	 -->	start_secondary()
					...
					cpu_startup_entry()
	  bringup_wait_for_ap()
	    wait_for_ap_thread() <--	  cpuhp_online_idle()
					  while (1)
					    do_idle()

					... available to run kthreads ...

	    stop_machine_unpark()
	      stopper->enable = true;

Close this by moving the stop_machine_unpark() into
cpuhp_online_idle(), such that the stopper thread is ready before we
start the idle loop and schedule.

Reported-by: "Paul E. McKenney" <paulmck@kernel.org>
Debugged-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: "Paul E. McKenney" <paulmck@kernel.org>
2019-12-17 13:32:50 +01:00
Linus Torvalds
168829ad09 Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
 "The main changes in this cycle were:

   - A comprehensive rewrite of the robust/PI futex code's exit handling
     to fix various exit races. (Thomas Gleixner et al)

   - Rework the generic REFCOUNT_FULL implementation using
     atomic_fetch_* operations so that the performance impact of the
     cmpxchg() loops is mitigated for common refcount operations.

     With these performance improvements the generic implementation of
     refcount_t should be good enough for everybody - and this got
     confirmed by performance testing, so remove ARCH_HAS_REFCOUNT and
     REFCOUNT_FULL entirely, leaving the generic implementation enabled
     unconditionally. (Will Deacon)

   - Other misc changes, fixes, cleanups"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  lkdtm: Remove references to CONFIG_REFCOUNT_FULL
  locking/refcount: Remove unused 'refcount_error_report()' function
  locking/refcount: Consolidate implementations of refcount_t
  locking/refcount: Consolidate REFCOUNT_{MAX,SATURATED} definitions
  locking/refcount: Move saturation warnings out of line
  locking/refcount: Improve performance of generic REFCOUNT_FULL code
  locking/refcount: Move the bulk of the REFCOUNT_FULL implementation into the <linux/refcount.h> header
  locking/refcount: Remove unused refcount_*_checked() variants
  locking/refcount: Ensure integer operands are treated as signed
  locking/refcount: Define constants for saturation and max refcount values
  futex: Prevent exit livelock
  futex: Provide distinct return value when owner is exiting
  futex: Add mutex around futex exit
  futex: Provide state handling for exec() as well
  futex: Sanitize exit state handling
  futex: Mark the begin of futex exit explicitly
  futex: Set task::futex_state to DEAD right after handling futex exit
  futex: Split futex_mm_release() for exit/exec
  exit/exec: Seperate mm_release()
  futex: Replace PF_EXITPIDONE with a state
  ...
2019-11-26 16:02:40 -08:00
Tyler Hicks
731dc9df97 cpu/speculation: Uninline and export CPU mitigations helpers
A kernel module may need to check the value of the "mitigations=" kernel
command line parameter as part of its setup when the module needs
to perform software mitigations for a CPU flaw.

Uninline and export the helper functions surrounding the cpu_mitigations
enum to allow for their usage from a module.

Lastly, privatize the enum and cpu_mitigations variable since the value of
cpu_mitigations can be checked with the exported helper functions.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2019-11-04 12:22:02 +01:00
Qian Cai
5facae4f35 locking/lockdep: Remove unused @nested argument from lock_release()
Since the following commit:

  b4adfe8e05 ("locking/lockdep: Remove unused argument in __lock_release")

@nested is no longer used in lock_release(), so remove it from all
lock_release() calls and friends.

Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: airlied@linux.ie
Cc: akpm@linux-foundation.org
Cc: alexander.levin@microsoft.com
Cc: daniel@iogearbox.net
Cc: davem@davemloft.net
Cc: dri-devel@lists.freedesktop.org
Cc: duyuyang@gmail.com
Cc: gregkh@linuxfoundation.org
Cc: hannes@cmpxchg.org
Cc: intel-gfx@lists.freedesktop.org
Cc: jack@suse.com
Cc: jlbec@evilplan.or
Cc: joonas.lahtinen@linux.intel.com
Cc: joseph.qi@linux.alibaba.com
Cc: jslaby@suse.com
Cc: juri.lelli@redhat.com
Cc: maarten.lankhorst@linux.intel.com
Cc: mark@fasheh.com
Cc: mhocko@kernel.org
Cc: mripard@kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: rodrigo.vivi@intel.com
Cc: sean@poorly.run
Cc: st@kernel.org
Cc: tj@kernel.org
Cc: tytso@mit.edu
Cc: vdavydov.dev@gmail.com
Cc: vincent.guittot@linaro.org
Cc: viro@zeniv.linux.org.uk
Link: https://lkml.kernel.org/r/1568909380-32199-1-git-send-email-cai@lca.pw
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-10-09 12:46:10 +02:00
Vitaly Kuznetsov
e1572f1d08 cpu/SMT: create and export cpu_smt_possible()
KVM needs to know if SMT is theoretically possible, this means it is
supported and not forcefully disabled ('nosmt=force'). Create and
export cpu_smt_possible() answering this question.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-09-24 13:37:28 +02:00
Thomas Gleixner
0c09ab96fc cpu/hotplug: Cache number of online CPUs
Re-evaluating the bitmap wheight of the online cpus bitmap in every
invocation of num_online_cpus() over and over is a pretty useless
exercise. Especially when num_online_cpus() is used in code paths
like the IPI delivery of x86 or the membarrier code.

Cache the number of online CPUs in the core and just return the cached
variable. The accessor function provides only a snapshot when used without
protection against concurrent CPU hotplug.

The storage needs to use an atomic_t because the kexec and reboot code
(ab)use set_cpu_online() in their 'shutdown' handlers without any form of
serialization as pointed out by Mathieu. Regular CPU hotplug usage is
properly serialized.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1907091622590.1634@nanos.tec.linutronix.de
2019-07-25 15:48:01 +02:00
Thomas Gleixner
e797bda3fd smp/hotplug: Track booted once CPUs in a cpumask
The booted once information which is required to deal with the MCE
broadcast issue on X86 correctly is stored in the per cpu hotplug state,
which is perfectly fine for the intended purpose.

X86 needs that information for supporting NMI broadcasting via shortcuts,
but retrieving it from per cpu data is cumbersome.

Move it to a cpumask so the information can be checked against the
cpu_present_mask quickly.

No functional change intended.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190722105219.818822855@linutronix.de
2019-07-25 15:47:37 +02:00
Linus Torvalds
e0e86b111b Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull SMP/hotplug updates from Thomas Gleixner:
 "A small set of updates for SMP and CPU hotplug:

   - Abort disabling secondary CPUs in the freezer when a wakeup is
     pending instead of evaluating it only after all CPUs have been
     offlined.

   - Remove the shared annotation for the strict per CPU cfd_data in the
     smp function call core code.

   - Remove the return values of smp_call_function() and on_each_cpu()
     as they are unconditionally 0. Fixup the few callers which actually
     bothered to check the return value"

* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  smp: Remove smp_call_function() and on_each_cpu() return values
  smp: Do not mark call_function_data as shared
  cpu/hotplug: Abort disabling secondary CPUs if wakeup is pending
  cpu/hotplug: Fix notify_cpu_starting() reference in bringup_wait_for_ap()
2019-07-08 10:39:56 -07:00
Eiichi Tsukata
33d4a5a7a5 cpu/hotplug: Fix out-of-bounds read when setting fail state
Setting invalid value to /sys/devices/system/cpu/cpuX/hotplug/fail
can control `struct cpuhp_step *sp` address, results in the following
global-out-of-bounds read.

Reproducer:

  # echo -2 > /sys/devices/system/cpu/cpu0/hotplug/fail

KASAN report:

  BUG: KASAN: global-out-of-bounds in write_cpuhp_fail+0x2cd/0x2e0
  Read of size 8 at addr ffffffff89734438 by task bash/1941

  CPU: 0 PID: 1941 Comm: bash Not tainted 5.2.0-rc6+ #31
  Call Trace:
   write_cpuhp_fail+0x2cd/0x2e0
   dev_attr_store+0x58/0x80
   sysfs_kf_write+0x13d/0x1a0
   kernfs_fop_write+0x2bc/0x460
   vfs_write+0x1e1/0x560
   ksys_write+0x126/0x250
   do_syscall_64+0xc1/0x390
   entry_SYSCALL_64_after_hwframe+0x49/0xbe
  RIP: 0033:0x7f05e4f4c970

  The buggy address belongs to the variable:
   cpu_hotplug_lock+0x98/0xa0

  Memory state around the buggy address:
   ffffffff89734300: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
   ffffffff89734380: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
  >ffffffff89734400: 00 00 00 00 fa fa fa fa 00 00 00 00 fa fa fa fa
                                          ^
   ffffffff89734480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
   ffffffff89734500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Add a sanity check for the value written from user space.

Fixes: 1db49484f2 ("smp/hotplug: Hotplug state fail injection")
Signed-off-by: Eiichi Tsukata <devel@etsukata.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Link: https://lkml.kernel.org/r/20190627024732.31672-1-devel@etsukata.com
2019-06-27 09:34:04 +02:00
Geert Uytterhoeven
1bf7272028 cpu/speculation: Warn on unsupported mitigations= parameter
Currently, if the user specifies an unsupported mitigation strategy on the
kernel command line, it will be ignored silently.  The code will fall back
to the default strategy, possibly leaving the system more vulnerable than
expected.

This may happen due to e.g. a simple typo, or, for a stable kernel release,
because not all mitigation strategies have been backported.

Inform the user by printing a message.

Fixes: 98af845294 ("cpu/speculation: Add 'mitigations=' cmdline option")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190516070935.22546-1-geert@linux-m68k.org
2019-06-26 16:56:21 +02:00
Pavankumar Kondeti
a66d955e91 cpu/hotplug: Abort disabling secondary CPUs if wakeup is pending
When "deep" suspend is enabled, all CPUs except the primary CPU are frozen
via CPU hotplug one by one. After all secondary CPUs are unplugged the
wakeup pending condition is evaluated and if pending the suspend operation
is aborted and the secondary CPUs are brought up again.

CPU hotplug is a slow operation, so it makes sense to check for wakeup
pending in the freezer loop before bringing down the next CPU. This
improves the system suspend abort latency significantly.

[ tglx: Massaged changelog and improved printk message ]

Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: iri Kosina <jkosina@suse.cz>
Cc: Mukesh Ojha <mojha@codeaurora.org>
Cc: linux-pm@vger.kernel.org
Link: https://lkml.kernel.org/r/1559536263-16472-1-git-send-email-pkondeti@codeaurora.org
2019-06-12 11:03:05 +02:00
Jiri Kosina
ec527c3180 x86/power: Fix 'nosmt' vs hibernation triple fault during resume
As explained in

	0cc3cd2165 ("cpu/hotplug: Boot HT siblings at least once")

we always, no matter what, have to bring up x86 HT siblings during boot at
least once in order to avoid first MCE bringing the system to its knees.

That means that whenever 'nosmt' is supplied on the kernel command-line,
all the HT siblings are as a result sitting in mwait or cpudile after
going through the online-offline cycle at least once.

This causes a serious issue though when a kernel, which saw 'nosmt' on its
commandline, is going to perform resume from hibernation: if the resume
from the hibernated image is successful, cr3 is flipped in order to point
to the address space of the kernel that is being resumed, which in turn
means that all the HT siblings are all of a sudden mwaiting on address
which is no longer valid.

That results in triple fault shortly after cr3 is switched, and machine
reboots.

Fix this by always waking up all the SMT siblings before initiating the
'restore from hibernation' process; this guarantees that all the HT
siblings will be properly carried over to the resumed kernel waiting in
resume_play_dead(), and acted upon accordingly afterwards, based on the
target kernel configuration.

Symmetricaly, the resumed kernel has to push the SMT siblings to mwait
again in case it has SMT disabled; this means it has to online all
the siblings when resuming (so that they come out of hlt) and offline
them again to let them reach mwait.

Cc: 4.19+ <stable@vger.kernel.org> # v4.19+
Debugged-by: Thomas Gleixner <tglx@linutronix.de>
Fixes: 0cc3cd2165 ("cpu/hotplug: Boot HT siblings at least once")
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2019-06-03 12:02:03 +02:00
Jiri Kosina
f560201102 cpu/hotplug: Fix notify_cpu_starting() reference in bringup_wait_for_ap()
bringup_wait_for_ap() comment references cpu_notify_starting(), but the 
function is actually called notify_cpu_starting(). Fix that.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1905282128100.1962@cbobk.fhfr.pm
2019-05-28 12:59:03 -07:00
Linus Torvalds
a0e928ed7c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Ingo Molnar:
 "This cycle had the following changes:

   - Timer tracing improvements (Anna-Maria Gleixner)

   - Continued tasklet reduction work: remove the hrtimer_tasklet
     (Thomas Gleixner)

   - Fix CPU hotplug remove race in the tick-broadcast mask handling
     code (Thomas Gleixner)

   - Force upper bound for setting CLOCK_REALTIME, to fix ABI
     inconsistencies with handling values that are close to the maximum
     supported and the vagueness of when uptime related wraparound might
     occur. Make the consistent maximum the year 2232 across all
     relevant ABIs and APIs. (Thomas Gleixner)

   - various cleanups and smaller fixes"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  tick: Fix typos in comments
  tick/broadcast: Fix warning about undefined tick_broadcast_oneshot_offline()
  timekeeping: Force upper bound for setting CLOCK_REALTIME
  timer/trace: Improve timer tracing
  timer/trace: Replace deprecated vsprintf pointer extension %pf by %ps
  timer: Move trace point to get proper index
  tick/sched: Update tick_sched struct documentation
  tick: Remove outgoing CPU from broadcast masks
  timekeeping: Consistently use unsigned int for seqcount snapshot
  softirq: Remove tasklet_hrtimer
  xfrm: Replace hrtimer tasklet with softirq hrtimer
  mac80211_hwsim: Replace hrtimer tasklet with softirq hrtimer
2019-05-06 14:50:46 -07:00
Linus Torvalds
5a2bf1abbf Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull CPU hotplug updates from Ingo Molnar:
 "Two changes in this cycle:

   - Make the /sys/devices/system/cpu/smt/* files available on all
     arches, so user space has a consistent way to detect whether SMT is
     enabled.

   - Sparse annotation fix"

* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  smpboot: Place the __percpu annotation correctly
  cpu/hotplug: Create SMT sysfs interface for all arches
2019-05-06 14:44:49 -07:00