sched/eevdf: Delayed dequeue task can't preempt

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Load balancing can migrate delayed dequeue tasks to even the load between
CPUs.

sched_balance_rq()
  -> detach_task()
    -> deactivate_task(DEQUEUE_NOCLOCK)
    -> set_task_cpu(dst_cpu)

  -> attach_task()
    -> activate_task(ENQUEUE_NOCLOCK)
    -> wakeup_preempt()

A delayed task with shorter slice can be dequeued during pick_next_entity()
but then jump to preempt because eligible.

Always jump to update for delayed dequeue task even with shorter slice.

Fixes: ba0d3bf5f9 ("sched/eevdf: Cancel slice protection if short slice task is eligible")
Reported-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20260701164920.1571352-1-vincent.guittot@linaro.org

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Vincent Guittot 2026-07-01 18:49:20 +02:00 • committed by Peter Zijlstra

parent 19b7bdc3a1

commit 04998aa548

1 changed files with 9 additions and 4 deletions

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kernel/sched/fair.c

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