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Commit c1804d54 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

sched: move_task_off_dead_cpu(): Remove retry logic 



The previous patch preserved the retry logic, but it looks unneeded.

__migrate_task() can only fail if we raced with migration after we dropped
the lock, but in this case the caller of set_cpus_allowed/etc must initiate
migration itself if ->on_rq == T.

We already fixed p->cpus_allowed, the changes in active/online masks must
be visible to racer, it should migrate the task to online cpu correctly.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100315091014.GA9138@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 1445c08d

kernel/sched.c

+6 −7
Original line number Diff line number Diff line
@@ -5456,7 +5456,7 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p) 
	struct rq *rq = cpu_rq(dead_cpu);

	int needs_cpu, uninitialized_var(dest_cpu);

	unsigned long flags;

again:



	local_irq_save(flags);



	raw_spin_lock(&rq->lock);
@@ -5464,14 +5464,13 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p) 
	if (needs_cpu)

		dest_cpu = select_fallback_rq(dead_cpu, p);

	raw_spin_unlock(&rq->lock);



	/* It can have affinity changed while we were choosing. */

	/*

	 * It can only fail if we race with set_cpus_allowed(),

	 * in the racer should migrate the task anyway.

	 */

	if (needs_cpu)

		needs_cpu = !__migrate_task(p, dead_cpu, dest_cpu);

		__migrate_task(p, dead_cpu, dest_cpu);

	local_irq_restore(flags);



	if (unlikely(needs_cpu))

		goto again;

}



/*