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Subject[PATCH] sched/fair: Fix detection of per-CPU kthreads waking a task
Date
select_idle_sibling() will return prev_cpu for the case where the task is
woken up by a per-CPU kthread. However, the idle task has been recently
modified and is now identified by is_per_cpu_kthread(), breaking the
behaviour described above. Using !is_idle_task() ensures we do not
spuriously trigger that select_idle_sibling() exit path.

Fixes: 00b89fe0197f ("sched: Make the idle task quack like a per-CPU kthread")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 945d987246c5..8bf95b0e368d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6399,6 +6399,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
* pattern is IO completions.
*/
if (is_per_cpu_kthread(current) &&
+ !is_idle_task(current) &&
prev == smp_processor_id() &&
this_rq()->nr_running <= 1) {
return prev;
--
2.25.1
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