sched: Fix delayed_dequeue vs switched_from_fair()

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Commit 2e0199df25 ("sched/fair: Prepare exit/cleanup paths for delayed_dequeue")
and its follow up fixes try to deal with a rather unfortunate
situation where is task is enqueued in a new class, even though it
shouldn't have been. Mostly because the existing ->switched_to/from()
hooks are in the wrong place for this case.

This all led to Paul being able to trigger failures at something like
once per 10k CPU hours of RCU torture.

For now, do the ugly thing and move the code to the right place by
ignoring the switch hooks.

Note: Clean up the whole sched_class::switch*_{to,from}() thing.

Fixes: 2e0199df25 ("sched/fair: Prepare exit/cleanup paths for delayed_dequeue")
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20241003185037.GA5594@noisy.programming.kicks-ass.net

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This commit is contained in:

Peter Zijlstra 2024-10-10 11:54:38 +02:00

parent 73ab05aa46

commit 98442f0ccd

5 changed files with 30 additions and 34 deletions

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33

kernel/sched/core.c

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4

kernel/sched/ext.c

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16

kernel/sched/fair.c

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2

kernel/sched/sched.h

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13

kernel/sched/syscalls.c

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