tree 4f20b106f92b74f80d3b033512ef58ffad252ffe
parent 9c7d9017a49fb8516c13b7bff59b7da2abed23e1
author Valentin Schneider <valentin.schneider@arm.com> 1610562701 +0000
committer Peter Zijlstra <peterz@infradead.org> 1611324581 +0100

sched/core: Print out straggler tasks in sched_cpu_dying()

Since commit

  1cf12e08bc4d ("sched/hotplug: Consolidate task migration on CPU unplug")

tasks are expected to move themselves out of a out-going CPU. For most
tasks this will be done automagically via BALANCE_PUSH, but percpu kthreads
will have to cooperate and move themselves away one way or another.

Currently, some percpu kthreads (workqueues being a notable exemple) do not
cooperate nicely and can end up on an out-going CPU at the time
sched_cpu_dying() is invoked.

Print the dying rq's tasks to shed some light on the stragglers.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210113183141.11974-1-valentin.schneider@arm.com