Several ->poll() implementations are special in that they use a
waitqueue whose lifetime is the current task, rather than the struct
file as is normally the case. This is okay for blocking polls, since a
blocking poll occurs within one task; however, non-blocking polls
require another solution. This solution is for the queue to be cleared
before it is freed, using 'wake_up_poll(wq, EPOLLHUP | POLLFREE);'.
However, that has a bug: wake_up_poll() calls __wake_up() with
nr_exclusive=1. Therefore, if there are multiple "exclusive" waiters,
and the wakeup function for the first one returns a positive value, only
that one will be called. That's *not* what's needed for POLLFREE;
POLLFREE is special in that it really needs to wake up everyone.
Considering the three non-blocking poll systems:
- io_uring poll doesn't handle POLLFREE at all, so it is broken anyway.
- aio poll is unaffected, since it doesn't support exclusive waits.
However, that's fragile, as someone could add this feature later.
- epoll doesn't appear to be broken by this, since its wakeup function
returns 0 when it sees POLLFREE. But this is fragile.
Although there is a workaround (see epoll), it's better to define a
function which always sends POLLFREE to all waiters. Add such a
function. Also make it verify that the queue really becomes empty after
all waiters have been woken up.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211209010455.42744-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Commit d81ae8aac8 ("sched/uclamp: Fix initialization of struct
uclamp_rq") introduced a bug where uclamp_max of the rq is not reset to
match the woken up task's uclamp_max when the rq is idle.
The code was relying on rq->uclamp_max initialized to zero, so on first
enqueue
static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
enum uclamp_id clamp_id)
{
...
if (uc_se->value > READ_ONCE(uc_rq->value))
WRITE_ONCE(uc_rq->value, uc_se->value);
}
was actually resetting it. But since commit d81ae8aac8 changed the
default to 1024, this no longer works. And since rq->uclamp_flags is
also initialized to 0, neither above code path nor uclamp_idle_reset()
update the rq->uclamp_max on first wake up from idle.
This is only visible from first wake up(s) until the first dequeue to
idle after enabling the static key. And it only matters if the
uclamp_max of this task is < 1024 since only then its uclamp_max will be
effectively ignored.
Fix it by properly initializing rq->uclamp_flags = UCLAMP_FLAG_IDLE to
ensure uclamp_idle_reset() is called which then will update the rq
uclamp_max value as expected.
Fixes: d81ae8aac8 ("sched/uclamp: Fix initialization of struct uclamp_rq")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20211202112033.1705279-1-qais.yousef@arm.com
__setup() callbacks expect 1 for success and 0 for failure. Correct the
usage here to reflect that.
Fixes: 826bfeb37b ("preempt/dynamic: Support dynamic preempt with preempt= boot option")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211203233203.133581-1-ahalaney@redhat.com
getrusage(RUSAGE_THREAD) with nohz_full may return shorter utime/stime
than the actual time.
task_cputime_adjusted() snapshots utime and stime and then adjust their
sum to match the scheduler maintained cputime.sum_exec_runtime.
Unfortunately in nohz_full, sum_exec_runtime is only updated once per
second in the worst case, causing a discrepancy against utime and stime
that can be updated anytime by the reader using vtime.
To fix this situation, perform an update of cputime.sum_exec_runtime
when the cputime snapshot reports the task as actually running while
the tick is disabled. The related overhead is then contained within the
relevant situations.
Reported-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Acked-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20211026141055.57358-3-frederic@kernel.org
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/
Commit c597bfddc9 ("sched: Provide Kconfig support for default dynamic
preempt mode") changed the selectable config names for the preemption
model. This means a config file must now select
CONFIG_PREEMPT_BEHAVIOUR=y
rather than
CONFIG_PREEMPT=y
to get a preemptible kernel. This means all arch config files would need to
be updated - right now they'll all end up with the default
CONFIG_PREEMPT_NONE_BEHAVIOUR.
Rather than touch a good hundred of config files, restore usage of
CONFIG_PREEMPT{_NONE, _VOLUNTARY}. Make them configure:
o The build-time preemption model when !PREEMPT_DYNAMIC
o The default boot-time preemption model when PREEMPT_DYNAMIC
Add siblings of those configs with the _BUILD suffix to unconditionally
designate the build-time preemption model (PREEMPT_DYNAMIC is built with
the "highest" preemption model it supports, aka PREEMPT). Downstream
configs should by now all be depending / selected by CONFIG_PREEMPTION
rather than CONFIG_PREEMPT, so only a few sites need patching up.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20211110202448.4054153-2-valentin.schneider@arm.com
Kevin is reporting crashes which point to a use-after-free of a cfs_rq
in update_blocked_averages(). Initial debugging revealed that we've
live cfs_rq's (on_list=1) in an about to be kfree()'d task group in
free_fair_sched_group(). However, it was unclear how that can happen.
His kernel config happened to lead to a layout of struct sched_entity
that put the 'my_q' member directly into the middle of the object
which makes it incidentally overlap with SLUB's freelist pointer.
That, in combination with SLAB_FREELIST_HARDENED's freelist pointer
mangling, leads to a reliable access violation in form of a #GP which
made the UAF fail fast.
Michal seems to have run into the same issue[1]. He already correctly
diagnosed that commit a7b359fc6a ("sched/fair: Correctly insert
cfs_rq's to list on unthrottle") is causing the preconditions for the
UAF to happen by re-adding cfs_rq's also to task groups that have no
more running tasks, i.e. also to dead ones. His analysis, however,
misses the real root cause and it cannot be seen from the crash
backtrace only, as the real offender is tg_unthrottle_up() getting
called via sched_cfs_period_timer() via the timer interrupt at an
inconvenient time.
When unregister_fair_sched_group() unlinks all cfs_rq's from the dying
task group, it doesn't protect itself from getting interrupted. If the
timer interrupt triggers while we iterate over all CPUs or after
unregister_fair_sched_group() has finished but prior to unlinking the
task group, sched_cfs_period_timer() will execute and walk the list of
task groups, trying to unthrottle cfs_rq's, i.e. re-add them to the
dying task group. These will later -- in free_fair_sched_group() -- be
kfree()'ed while still being linked, leading to the fireworks Kevin
and Michal are seeing.
To fix this race, ensure the dying task group gets unlinked first.
However, simply switching the order of unregistering and unlinking the
task group isn't sufficient, as concurrent RCU walkers might still see
it, as can be seen below:
CPU1: CPU2:
: timer IRQ:
: do_sched_cfs_period_timer():
: :
: distribute_cfs_runtime():
: rcu_read_lock();
: :
: unthrottle_cfs_rq():
sched_offline_group(): :
: walk_tg_tree_from(…,tg_unthrottle_up,…):
list_del_rcu(&tg->list); :
(1) : list_for_each_entry_rcu(child, &parent->children, siblings)
: :
(2) list_del_rcu(&tg->siblings); :
: tg_unthrottle_up():
unregister_fair_sched_group(): struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
: :
list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); :
: :
: if (!cfs_rq_is_decayed(cfs_rq) || cfs_rq->nr_running)
(3) : list_add_leaf_cfs_rq(cfs_rq);
: :
: :
: :
: :
: :
(4) : rcu_read_unlock();
CPU 2 walks the task group list in parallel to sched_offline_group(),
specifically, it'll read the soon to be unlinked task group entry at
(1). Unlinking it on CPU 1 at (2) therefore won't prevent CPU 2 from
still passing it on to tg_unthrottle_up(). CPU 1 now tries to unlink
all cfs_rq's via list_del_leaf_cfs_rq() in
unregister_fair_sched_group(). Meanwhile CPU 2 will re-add some of
these at (3), which is the cause of the UAF later on.
To prevent this additional race from happening, we need to wait until
walk_tg_tree_from() has finished traversing the task groups, i.e.
after the RCU read critical section ends in (4). Afterwards we're safe
to call unregister_fair_sched_group(), as each new walk won't see the
dying task group any more.
On top of that, we need to wait yet another RCU grace period after
unregister_fair_sched_group() to ensure print_cfs_stats(), which might
run concurrently, always sees valid objects, i.e. not already free'd
ones.
This patch survives Michal's reproducer[2] for 8h+ now, which used to
trigger within minutes before.
[1] https://lore.kernel.org/lkml/20211011172236.11223-1-mkoutny@suse.com/
[2] https://lore.kernel.org/lkml/20211102160228.GA57072@blackbody.suse.cz/
Fixes: a7b359fc6a ("sched/fair: Correctly insert cfs_rq's to list on unthrottle")
[peterz: shuffle code around a bit]
Reported-by: Kevin Tanguy <kevin.tanguy@corp.ovh.com>
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Nothing protects the access to the per_cpu variable sd_llc_id. When testing
the same CPU (i.e. this_cpu == that_cpu), a race condition exists with
update_top_cache_domain(). One scenario being:
CPU1 CPU2
==================================================================
per_cpu(sd_llc_id, CPUX) => 0
partition_sched_domains_locked()
detach_destroy_domains()
cpus_share_cache(CPUX, CPUX) update_top_cache_domain(CPUX)
per_cpu(sd_llc_id, CPUX) => 0
per_cpu(sd_llc_id, CPUX) = CPUX
per_cpu(sd_llc_id, CPUX) => CPUX
return false
ttwu_queue_cond() wouldn't catch smp_processor_id() == cpu and the result
is a warning triggered from ttwu_queue_wakelist().
Avoid a such race in cpus_share_cache() by always returning true when
this_cpu == that_cpu.
Fixes: 518cd62341 ("sched: Only queue remote wakeups when crossing cache boundaries")
Reported-by: Jing-Ting Wu <jing-ting.wu@mediatek.com>
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211104175120.857087-1-vincent.donnefort@arm.com
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Merge tag 'kernel.sys.v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull prctl updates from Christian Brauner:
"This contains the missing prctl uapi pieces for PR_SCHED_CORE.
In order to activate core scheduling the caller is expected to specify
the scope of the new core scheduling domain.
For example, passing 2 in the 4th argument of
prctl(PR_SCHED_CORE, PR_SCHED_CORE_CREATE, <pid>, 2, 0);
would indicate that the new core scheduling domain encompasses all
tasks in the process group of <pid>. Specifying 0 would only create a
core scheduling domain for the thread identified by <pid> and 2 would
encompass the whole thread-group of <pid>.
Note, the values 0, 1, and 2 correspond to PIDTYPE_PID, PIDTYPE_TGID,
and PIDTYPE_PGID. A first version tried to expose those values
directly to which I objected because:
- PIDTYPE_* is an enum that is kernel internal which we should not
expose to userspace directly.
- PIDTYPE_* indicates what a given struct pid is used for it doesn't
express a scope.
But what the 4th argument of PR_SCHED_CORE prctl() expresses is the
scope of the operation, i.e. the scope of the core scheduling domain
at creation time. So Eugene's patch now simply introduces three new
defines PR_SCHED_CORE_SCOPE_THREAD, PR_SCHED_CORE_SCOPE_THREAD_GROUP,
and PR_SCHED_CORE_SCOPE_PROCESS_GROUP. They simply express what
happens.
This has been on the mailing list for quite a while with all relevant
scheduler folks Cced. I announced multiple times that I'd pick this up
if I don't see or her anyone else doing it. None of this touches
proper scheduler code but only concerns uapi so I think this is fine.
With core scheduling being quite common now for vm managers (e.g.
moving individual vcpu threads into their own core scheduling domain)
and container managers (e.g. moving the init process into its own core
scheduling domain and letting all created children inherit it) having
to rely on raw numbers passed as the 4th argument in prctl() is a bit
annoying and everyone is starting to come up with their own defines"
* tag 'kernel.sys.v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
uapi/linux/prctl: provide macro definitions for the PR_SCHED_CORE type argument
Merge misc updates from Andrew Morton:
"257 patches.
Subsystems affected by this patch series: scripts, ocfs2, vfs, and
mm (slab-generic, slab, slub, kconfig, dax, kasan, debug, pagecache,
gup, swap, memcg, pagemap, mprotect, mremap, iomap, tracing, vmalloc,
pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, tools,
memblock, oom-kill, hugetlbfs, migration, thp, readahead, nommu, ksm,
vmstat, madvise, memory-hotplug, rmap, zsmalloc, highmem, zram,
cleanups, kfence, and damon)"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (257 commits)
mm/damon: remove return value from before_terminate callback
mm/damon: fix a few spelling mistakes in comments and a pr_debug message
mm/damon: simplify stop mechanism
Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions
Docs/admin-guide/mm/damon/start: simplify the content
Docs/admin-guide/mm/damon/start: fix a wrong link
Docs/admin-guide/mm/damon/start: fix wrong example commands
mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on
mm/damon: remove unnecessary variable initialization
Documentation/admin-guide/mm/damon: add a document for DAMON_RECLAIM
mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)
selftests/damon: support watermarks
mm/damon/dbgfs: support watermarks
mm/damon/schemes: activate schemes based on a watermarks mechanism
tools/selftests/damon: update for regions prioritization of schemes
mm/damon/dbgfs: support prioritization weights
mm/damon/vaddr,paddr: support pageout prioritization
mm/damon/schemes: prioritize regions within the quotas
mm/damon/selftests: support schemes quotas
mm/damon/dbgfs: support quotas of schemes
...
Patch series "Fix NUMA without SMP".
SuperH is the only architecture which still supports NUMA without SMP,
for good reasons (various memories scattered around the address space,
each with varying latencies).
This series fixes two build errors due to variables and functions used
by the NUMA code being provided by SMP-only source files or sections.
This patch (of 2):
If CONFIG_NUMA=y, but CONFIG_SMP=n (e.g. sh/migor_defconfig):
sh4-linux-gnu-ld: mm/page_alloc.o: in function `get_page_from_freelist':
page_alloc.c:(.text+0x2c24): undefined reference to `node_reclaim_distance'
Fix this by moving the declaration of node_reclaim_distance from an
SMP-only to a generic file.
Link: https://lkml.kernel.org/r/cover.1631781495.git.geert+renesas@glider.be
Link: https://lkml.kernel.org/r/6432666a648dde85635341e6c918cee97c97d264.1631781495.git.geert+renesas@glider.be
Fixes: a55c7454a8 ("sched/topology: Improve load balancing on AMD EPYC systems")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Suggested-by: Matt Fleming <matt@codeblueprint.co.uk>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Cc: Rich Felker <dalias@libc.org>
Cc: Gon Solo <gonsolo@gmail.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cross-architecture update to move task_struct::cpu back into thread_info
on arm64, x86, s390, powerpc, and riscv. All Acked by arch maintainers.
Quoting Ard Biesheuvel:
"Move task_struct::cpu back into thread_info
Keeping CPU in task_struct is problematic for architectures that define
raw_smp_processor_id() in terms of this field, as it requires
linux/sched.h to be included, which causes a lot of pain in terms of
circular dependencies (aka 'header soup')
This series moves it back into thread_info (where it came from) for all
architectures that enable THREAD_INFO_IN_TASK, addressing the header
soup issue as well as some pointless differences in the implementations
of task_cpu() and set_task_cpu()."
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Merge tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull thread_info update to move 'cpu' back from task_struct from Kees Cook:
"Cross-architecture update to move task_struct::cpu back into
thread_info on arm64, x86, s390, powerpc, and riscv. All Acked by arch
maintainers.
Quoting Ard Biesheuvel:
'Move task_struct::cpu back into thread_info
Keeping CPU in task_struct is problematic for architectures that
define raw_smp_processor_id() in terms of this field, as it
requires linux/sched.h to be included, which causes a lot of pain
in terms of circular dependencies (aka 'header soup')
This series moves it back into thread_info (where it came from)
for all architectures that enable THREAD_INFO_IN_TASK, addressing
the header soup issue as well as some pointless differences in the
implementations of task_cpu() and set_task_cpu()'"
* tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
riscv: rely on core code to keep thread_info::cpu updated
powerpc: smp: remove hack to obtain offset of task_struct::cpu
sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y
powerpc: add CPU field to struct thread_info
s390: add CPU field to struct thread_info
x86: add CPU field to struct thread_info
arm64: add CPU field to struct thread_info
- Revert the printk format based wchan() symbol resolution as it can leak
the raw value in case that the symbol is not resolvable.
- Make wchan() more robust and work with all kind of unwinders by
enforcing that the task stays blocked while unwinding is in progress.
- Prevent sched_fork() from accessing an invalid sched_task_group
- Improve asymmetric packing logic
- Extend scheduler statistics to RT and DL scheduling classes and add
statistics for bandwith burst to the SCHED_FAIR class.
- Properly account SCHED_IDLE entities
- Prevent a potential deadlock when initial priority is assigned to a
newly created kthread. A recent change to plug a race between cpuset and
__sched_setscheduler() introduced a new lock dependency which is now
triggered. Break the lock dependency chain by moving the priority
assignment to the thread function.
- Fix the idle time reporting in /proc/uptime for NOHZ enabled systems.
- Improve idle balancing in general and especially for NOHZ enabled
systems.
- Provide proper interfaces for live patching so it does not have to
fiddle with scheduler internals.
- Add cluster aware scheduling support.
- A small set of tweaks for RT (irqwork, wait_task_inactive(), various
scheduler options and delaying mmdrop)
- The usual small tweaks and improvements all over the place
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Merge tag 'sched-core-2021-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Thomas Gleixner:
- Revert the printk format based wchan() symbol resolution as it can
leak the raw value in case that the symbol is not resolvable.
- Make wchan() more robust and work with all kind of unwinders by
enforcing that the task stays blocked while unwinding is in progress.
- Prevent sched_fork() from accessing an invalid sched_task_group
- Improve asymmetric packing logic
- Extend scheduler statistics to RT and DL scheduling classes and add
statistics for bandwith burst to the SCHED_FAIR class.
- Properly account SCHED_IDLE entities
- Prevent a potential deadlock when initial priority is assigned to a
newly created kthread. A recent change to plug a race between cpuset
and __sched_setscheduler() introduced a new lock dependency which is
now triggered. Break the lock dependency chain by moving the priority
assignment to the thread function.
- Fix the idle time reporting in /proc/uptime for NOHZ enabled systems.
- Improve idle balancing in general and especially for NOHZ enabled
systems.
- Provide proper interfaces for live patching so it does not have to
fiddle with scheduler internals.
- Add cluster aware scheduling support.
- A small set of tweaks for RT (irqwork, wait_task_inactive(), various
scheduler options and delaying mmdrop)
- The usual small tweaks and improvements all over the place
* tag 'sched-core-2021-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (69 commits)
sched/fair: Cleanup newidle_balance
sched/fair: Remove sysctl_sched_migration_cost condition
sched/fair: Wait before decaying max_newidle_lb_cost
sched/fair: Skip update_blocked_averages if we are defering load balance
sched/fair: Account update_blocked_averages in newidle_balance cost
x86: Fix __get_wchan() for !STACKTRACE
sched,x86: Fix L2 cache mask
sched/core: Remove rq_relock()
sched: Improve wake_up_all_idle_cpus() take #2
irq_work: Also rcuwait for !IRQ_WORK_HARD_IRQ on PREEMPT_RT
irq_work: Handle some irq_work in a per-CPU thread on PREEMPT_RT
irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support.
sched/rt: Annotate the RT balancing logic irqwork as IRQ_WORK_HARD_IRQ
sched: Add cluster scheduler level for x86
sched: Add cluster scheduler level in core and related Kconfig for ARM64
topology: Represent clusters of CPUs within a die
sched: Disable -Wunused-but-set-variable
sched: Add wrapper for get_wchan() to keep task blocked
x86: Fix get_wchan() to support the ORC unwinder
proc: Use task_is_running() for wchan in /proc/$pid/stat
...
- Move futex code into kernel/futex/ and split up the kitchen sink into
seperate files to make integration of sys_futex_waitv() simpler.
- Add a new sys_futex_waitv() syscall which allows to wait on multiple
futexes. The main use case is emulating Windows' WaitForMultipleObjects
which allows Wine to improve the performance of Windows Games. Also
native Linux games can benefit from this interface as this is a common
wait pattern for this kind of applications.
- Add context to ww_mutex_trylock() to provide a path for i915 to rework
their eviction code step by step without making lockdep upset until the
final steps of rework are completed. It's also useful for regulator and
TTM to avoid dropping locks in the non contended path.
- Lockdep and might_sleep() cleanups and improvements
- A few improvements for the RT substitutions.
- The usual small improvements and cleanups.
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Merge tag 'locking-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Thomas Gleixner:
- Move futex code into kernel/futex/ and split up the kitchen sink into
seperate files to make integration of sys_futex_waitv() simpler.
- Add a new sys_futex_waitv() syscall which allows to wait on multiple
futexes.
The main use case is emulating Windows' WaitForMultipleObjects which
allows Wine to improve the performance of Windows Games. Also native
Linux games can benefit from this interface as this is a common wait
pattern for this kind of applications.
- Add context to ww_mutex_trylock() to provide a path for i915 to
rework their eviction code step by step without making lockdep upset
until the final steps of rework are completed. It's also useful for
regulator and TTM to avoid dropping locks in the non contended path.
- Lockdep and might_sleep() cleanups and improvements
- A few improvements for the RT substitutions.
- The usual small improvements and cleanups.
* tag 'locking-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
locking: Remove spin_lock_flags() etc
locking/rwsem: Fix comments about reader optimistic lock stealing conditions
locking: Remove rcu_read_{,un}lock() for preempt_{dis,en}able()
locking/rwsem: Disable preemption for spinning region
docs: futex: Fix kernel-doc references
futex: Fix PREEMPT_RT build
futex2: Documentation: Document sys_futex_waitv() uAPI
selftests: futex: Test sys_futex_waitv() wouldblock
selftests: futex: Test sys_futex_waitv() timeout
selftests: futex: Add sys_futex_waitv() test
futex,arm: Wire up sys_futex_waitv()
futex,x86: Wire up sys_futex_waitv()
futex: Implement sys_futex_waitv()
futex: Simplify double_lock_hb()
futex: Split out wait/wake
futex: Split out requeue
futex: Rename mark_wake_futex()
futex: Rename: match_futex()
futex: Rename: hb_waiter_{inc,dec,pending}()
futex: Split out PI futex
...
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Merge tag 'for-5.16/block-2021-10-29' of git://git.kernel.dk/linux-block
Pull block updates from Jens Axboe:
- mq-deadline accounting improvements (Bart)
- blk-wbt timer fix (Andrea)
- Untangle the block layer includes (Christoph)
- Rework the poll support to be bio based, which will enable adding
support for polling for bio based drivers (Christoph)
- Block layer core support for multi-actuator drives (Damien)
- blk-crypto improvements (Eric)
- Batched tag allocation support (me)
- Request completion batching support (me)
- Plugging improvements (me)
- Shared tag set improvements (John)
- Concurrent queue quiesce support (Ming)
- Cache bdev in ->private_data for block devices (Pavel)
- bdev dio improvements (Pavel)
- Block device invalidation and block size improvements (Xie)
- Various cleanups, fixes, and improvements (Christoph, Jackie,
Masahira, Tejun, Yu, Pavel, Zheng, me)
* tag 'for-5.16/block-2021-10-29' of git://git.kernel.dk/linux-block: (174 commits)
blk-mq-debugfs: Show active requests per queue for shared tags
block: improve readability of blk_mq_end_request_batch()
virtio-blk: Use blk_validate_block_size() to validate block size
loop: Use blk_validate_block_size() to validate block size
nbd: Use blk_validate_block_size() to validate block size
block: Add a helper to validate the block size
block: re-flow blk_mq_rq_ctx_init()
block: prefetch request to be initialized
block: pass in blk_mq_tags to blk_mq_rq_ctx_init()
block: add rq_flags to struct blk_mq_alloc_data
block: add async version of bio_set_polled
block: kill DIO_MULTI_BIO
block: kill unused polling bits in __blkdev_direct_IO()
block: avoid extra iter advance with async iocb
block: Add independent access ranges support
blk-mq: don't issue request directly in case that current is to be blocked
sbitmap: silence data race warning
blk-cgroup: synchronize blkg creation against policy deactivation
block: refactor bio_iov_bvec_set()
block: add single bio async direct IO helper
...
update_next_balance() uses sd->last_balance which is not modified by
load_balance() so we can merge the 2 calls in one place.
No functional change
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-6-vincent.guittot@linaro.org
With a default value of 500us, sysctl_sched_migration_cost is
significanlty higher than the cost of load_balance. Remove the
condition and rely on the sd->max_newidle_lb_cost to abort
newidle_balance.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-5-vincent.guittot@linaro.org
Decay max_newidle_lb_cost only when it has not been updated for a while
and ensure to not decay a recently changed value.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-4-vincent.guittot@linaro.org
In newidle_balance(), the scheduler skips load balance to the new idle cpu
when the 1st sd of this_rq is:
this_rq->avg_idle < sd->max_newidle_lb_cost
Doing a costly call to update_blocked_averages() will not be useful and
simply adds overhead when this condition is true.
Check the condition early in newidle_balance() to skip
update_blocked_averages() when possible.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-3-vincent.guittot@linaro.org
The time spent to update the blocked load can be significant depending of
the complexity fo the cgroup hierarchy. Take this time into account in
the cost of the 1st load balance of a newly idle cpu.
Also reduce the number of call to sched_clock_cpu() and track more actual
work.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-2-vincent.guittot@linaro.org
Consolidate the various helpers into a single blk_flush_plug helper that
takes a plk_plug and the from_scheduler bool and switch all callsites to
call it directly. Checks that the plug is non-NULL must be performed by
the caller, something that most already do anyway.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211020144119.142582-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit f1a0a376ca ("sched/core: Initialize the idle task with
preemption disabled") removed the init_idle() call from
idle_thread_get(). This was the sole call-path on hotplug that resets
the Shadow Call Stack (scs) Stack Pointer (sp).
Not resetting the scs-sp leads to scs overflow after enough hotplug
cycles. Therefore add an explicit scs_task_reset() to the hotplug code
to make sure the scs-sp does get reset on hotplug.
Fixes: f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")
Signed-off-by: Woody Lin <woodylin@google.com>
[peterz: Changelog]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20211012083521.973587-1-woodylin@google.com
Only core.c needs blkdev.h, so move the #include statement there.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210920123328.1399408-8-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The push-IPI logic for RT tasks expects to be invoked from hardirq
context. One reason is that a RT task on the remote CPU would block the
softirq processing on PREEMPT_RT and so avoid pulling / balancing the RT
tasks as intended.
Annotate root_domain::rto_push_work as IRQ_WORK_HARD_IRQ.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211006111852.1514359-2-bigeasy@linutronix.de
The compilers can't deal with obvious DCE vs that warning, resulting
in code like:
if (0) {
sched sched_statistics *stats;
stats = __schedstats_from_se(se);
...
}
triggering the warning. Kill the warning to make the robots stop
reporting this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lkml.kernel.org/r/YWWPLnaZGybHsTkv@hirez.programming.kicks-ass.net
Having a stable wchan means the process must be blocked and for it to
stay that way while performing stack unwinding.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> [arm]
Tested-by: Mark Rutland <mark.rutland@arm.com> [arm64]
Link: https://lkml.kernel.org/r/20211008111626.332092234@infradead.org
There is a small race between copy_process() and sched_fork()
where child->sched_task_group point to an already freed pointer.
parent doing fork() | someone moving the parent
| to another cgroup
-------------------------------+-------------------------------
copy_process()
+ dup_task_struct()<1>
parent move to another cgroup,
and free the old cgroup. <2>
+ sched_fork()
+ __set_task_cpu()<3>
+ task_fork_fair()
+ sched_slice()<4>
In the worst case, this bug can lead to "use-after-free" and
cause panic as shown above:
(1) parent copy its sched_task_group to child at <1>;
(2) someone move the parent to another cgroup and free the old
cgroup at <2>;
(3) the sched_task_group and cfs_rq that belong to the old cgroup
will be accessed at <3> and <4>, which cause a panic:
[] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
[] PGD 8000001fa0a86067 P4D 8000001fa0a86067 PUD 2029955067 PMD 0
[] Oops: 0000 [#1] SMP PTI
[] CPU: 7 PID: 648398 Comm: ebizzy Kdump: loaded Tainted: G OE --------- - - 4.18.0.x86_64+ #1
[] RIP: 0010:sched_slice+0x84/0xc0
[] Call Trace:
[] task_fork_fair+0x81/0x120
[] sched_fork+0x132/0x240
[] copy_process.part.5+0x675/0x20e0
[] ? __handle_mm_fault+0x63f/0x690
[] _do_fork+0xcd/0x3b0
[] do_syscall_64+0x5d/0x1d0
[] entry_SYSCALL_64_after_hwframe+0x65/0xca
[] RIP: 0033:0x7f04418cd7e1
Between cgroup_can_fork() and cgroup_post_fork(), the cgroup
membership and thus sched_task_group can't change. So update child's
sched_task_group at sched_post_fork() and move task_fork() and
__set_task_cpu() (where accees the sched_task_group) from sched_fork()
to sched_post_fork().
Fixes: 8323f26ce3 ("sched: Fix race in task_group")
Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lkml.kernel.org/r/20210915064030.2231-1-zhangqiao22@huawei.com
numa_distance in cpu_attach_domain() is introduced in
commit b5b217346d ("sched/topology: Warn when NUMA diameter > 2")
to warn user when NUMA diameter > 2 as we'll misrepresent
the scheduler topology structures at that time. This is
fixed by Barry in commit 585b6d2723 ("sched/topology: fix the issue
groups don't span domain->span for NUMA diameter > 2") and
numa_distance is unused now. So remove it.
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20210915063158.80639-1-yangyicong@hisilicon.com
Fix a few comments to help understand them better.
Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20211004105706.3669-4-bharata@amd.com
numa_group::fault_cpus is actually a pointer to the region
in numa_group::faults[] where NUMA_CPU stats are located.
Remove this redundant member and use numa_group::faults[NUMA_CPU]
directly like it is done for similar per-process numa fault stats.
There is no functionality change due to this commit.
Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20211004105706.3669-3-bharata@amd.com
While allocating group fault stats, task_numa_group()
is using a hard coded number 4. Replace this by
NR_NUMA_HINT_FAULT_STATS.
No functionality change in this commit.
Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20211004105706.3669-2-bharata@amd.com
Simplify and make wake_up_if_idle() more robust, also don't iterate
the whole machine with preempt_disable() in it's caller:
wake_up_all_idle_cpus().
This prepares for another wake_up_if_idle() user that needs a full
do_idle() cycle.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.769328779@infradead.org
Give try_invoke_on_locked_down_task() a saner name and have it return
an int so that the caller might distinguish between different reasons
of failure.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.649944917@infradead.org
Clarify and tighten try_invoke_on_locked_down_task().
Basically the function calls @func under task_rq_lock(), except it
avoids taking rq->lock when possible.
This makes calling @func unconditional (the function will get renamed
in a later patch to remove the try).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.589323576@infradead.org
When !SCHEDSTATS schedstat_enabled() is an unconditional 0 and the
whole block doesn't exist, however GCC figures the scoped variable
'stats' is unused and complains about it.
Upgrade the warning from -Wunused-variable to -Wunused-but-set-variable
by writing it in two statements. This fixes the build because the new
warning is in W=1.
Given that whole if(0) {} thing, I don't feel motivated to change
things overly much and quite strongly feel this is the compiler being
daft.
Fixes: cb3e971c435d ("sched: Make struct sched_statistics independent of fair sched class")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Since commit 89aafd67f2 ("sched/fair: Use prev instead of new target as recent_used_cpu"),
p->recent_used_cpu is unconditionnaly set with prev.
Fixes: 89aafd67f2 ("sched/fair: Use prev instead of new target as recent_used_cpu")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20210928103544.27489-1-vincent.guittot@linaro.org
Neither wq_worker_sleeping() nor io_wq_worker_sleeping() require to be invoked
with preemption disabled:
- The worker flag checks operations only need to be serialized against
the worker thread itself.
- The accounting and worker pool operations are serialized with locks.
which means that disabling preemption has neither a reason nor a
value. Remove it and update the stale comment.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lkml.kernel.org/r/8735pnafj7.ffs@tglx
Doing cleanups in the tail of schedule() is a latency punishment for the
incoming task. The point of invoking kprobes_task_flush() for a dead task
is that the instances are returned and cannot leak when __schedule() is
kprobed.
Move it into the delayed cleanup.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.537994026@linutronix.de
The queued remote wakeup mechanism has turned out to be suboptimal for RT
enabled kernels. The maximum latencies go up by a factor of > 5x in certain
scenarious.
This is caused by either long wake lists or by a large number of TTWU IPIs
which are processed back to back.
Disable it for RT.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.482262764@linutronix.de
Batched task migrations are a source for large latencies as they keep the
scheduler from running while processing the migrations.
Limit the batch size to 8 instead of 32 when running on a RT enabled
kernel.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.425097596@linutronix.de
mmdrop() is invoked from finish_task_switch() by the incoming task to drop
the mm which was handed over by the previous task. mmdrop() can be quite
expensive which prevents an incoming real-time task from getting useful
work done.
Provide mmdrop_sched() which maps to mmdrop() on !RT kernels. On RT kernels
it delagates the eventually required invocation of __mmdrop() to RCU.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.648582026@linutronix.de
Make cookie functions static as these are no longer invoked directly
by other code.
No functional change intended.
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210922085735.52812-1-zhangshaokun@hisilicon.com
When deciding to pull tasks in ASYM_PACKING, it is necessary not only to
check for the idle state of the destination CPU, dst_cpu, but also of
its SMT siblings.
If dst_cpu is idle but its SMT siblings are busy, performance suffers
if it pulls tasks from a medium priority CPU that does not have SMT
siblings.
Implement asym_smt_can_pull_tasks() to inspect the state of the SMT
siblings of both dst_cpu and the CPUs in the candidate busiest group.
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-7-ricardo.neri-calderon@linux.intel.com
Create a separate function, sched_asym(). A subsequent changeset will
introduce logic to deal with SMT in conjunction with asmymmetric
packing. Such logic will need the statistics of the scheduling
group provided as argument. Update them before calling sched_asym().
Co-developed-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-6-ricardo.neri-calderon@linux.intel.com
Before deciding to pull tasks when using asymmetric packing of tasks,
on some architectures (e.g., x86) it is necessary to know not only the
state of dst_cpu but also of its SMT siblings. The decision to classify
a candidate busiest group as group_asym_packing is done in
update_sg_lb_stats(). Give this function access to the scheduling domain
statistics, which contains the statistics of the local group.
Originally-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-5-ricardo.neri-calderon@linux.intel.com
sched_asmy_prefer() always returns false when called on the local group. By
checking local_group, we can avoid additional checks and invoking
sched_asmy_prefer() when it is not needed. No functional changes are
introduced.
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-4-ricardo.neri-calderon@linux.intel.com
There exist situations in which the load balance needs to know the
properties of the CPUs in a scheduling group. When using asymmetric
packing, for instance, the load balancer needs to know not only the
state of dst_cpu but also of its SMT siblings, if any.
Use the flags of the child scheduling domains to initialize scheduling
group flags. This will reflect the properties of the CPUs in the
group.
A subsequent changeset will make use of these new flags. No functional
changes are introduced.
Originally-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Len Brown <len.brown@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210911011819.12184-3-ricardo.neri-calderon@linux.intel.com
Currently the boot defined preempt behaviour (aka dynamic preempt)
selects full preemption by default when the "preempt=" boot parameter
is omitted. However distros may rather want to default to either
no preemption or voluntary preemption.
To provide with this flexibility, make dynamic preemption a visible
Kconfig option and adapt the preemption behaviour selected by the user
to either static or dynamic preemption.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210914103134.11309-1-frederic@kernel.org
Eric Biggers