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| author |   Vincent Donnefort <vincent.donnefort@arm.com> | 2021-12-01 14:34:50 +0000 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2021-12-04 10:56:20 +0100 |
| commit | 8b4e74ccb582797f6f0b0a50372ebd9fd2372a27 (patch) | |
| tree | 5cab618e8b82885b30fc9d00a42729e8e9a3fb23 /kernel/sched | |
| parent | sched/cpuacct: Make user/system times in cpuacct.stat more precise (diff) | |
| download | linux-dev-8b4e74ccb582797f6f0b0a50372ebd9fd2372a27.tar.xz linux-dev-8b4e74ccb582797f6f0b0a50372ebd9fd2372a27.zip | |
sched/fair: Fix detection of per-CPU kthreads waking a task
select_idle_sibling() has a special case for tasks woken up by a per-CPU
kthread, where the selected CPU is the previous one. However, the current
condition for this exit path is incomplete. A task can wake up from an
interrupt context (e.g. hrtimer), while a per-CPU kthread is running. A
such scenario would spuriously trigger the special case described above.
Also, a recent change made the idle task like a regular per-CPU kthread,
hence making that situation more likely to happen
(is_per_cpu_kthread(swapper) being true now).
Checking for task context makes sure select_idle_sibling() will not
interpret a wake up from any other context as a wake up by a per-CPU
kthread.
Fixes: 52262ee567ad ("sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20211201143450.479472-1-vincent.donnefort@arm.com
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/fair.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 884f29d07963..5cd27986b43e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6398,6 +6398,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target) * pattern is IO completions. */ if (is_per_cpu_kthread(current) && + in_task() && prev == smp_processor_id() && this_rq()->nr_running <= 1) { return prev; |