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| author | Vincent Donnefort <vincent.donnefort@arm.com> | 2021-12-01 14:34:50 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-01-27 10:53:53 +0100 |
| commit | d7d5b3bc5263cb82c5673e5972aba543f96199fa (patch) | |
| tree | 7f5126aba2270416808913641fb347b873e36a6e /kernel | |
| parent | ec121517ac8d95a67a1b6ee6dc3102d64a4aa87b (diff) | |
sched/fair: Fix detection of per-CPU kthreads waking a task
[ Upstream commit 8b4e74ccb582797f6f0b0a50372ebd9fd2372a27 ]
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
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel')
| -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 c004e3b89c32..a7589552be5f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6284,6 +6284,7 @@ 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; |