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Commit 8f42ced9 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Drop rq->lock from sched_exec() 



Since we can now call select_task_rq() and set_task_cpu() with only
p->pi_lock held, and sched_exec() load-balancing has always been
optimistic, drop all rq->lock usage.

Oleg also noted that need_migrate_task() will always be true for
current, so don't bother calling that at all.

Reviewed-by: default avatarFrank Rowand <frank.rowand@am.sony.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20110405152729.314204889@chello.nl


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent ab2515c4

kernel/sched.c

+5 −10
Original line number Diff line number Diff line
@@ -3465,27 +3465,22 @@ void sched_exec(void) 
{

	struct task_struct *p = current;

	unsigned long flags;

	struct rq *rq;

	int dest_cpu;



	rq = task_rq_lock(p, &flags);

	raw_spin_lock_irqsave(&p->pi_lock, flags);

	dest_cpu = p->sched_class->select_task_rq(p, SD_BALANCE_EXEC, 0);

	if (dest_cpu == smp_processor_id())

		goto unlock;



	/*

	 * select_task_rq() can race against ->cpus_allowed

	 */

	if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed) &&

	    likely(cpu_active(dest_cpu)) && need_migrate_task(p)) {

	if (likely(cpu_active(dest_cpu))) {

		struct migration_arg arg = { p, dest_cpu };



		task_rq_unlock(rq, p, &flags);

		stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);

		raw_spin_unlock_irqrestore(&p->pi_lock, flags);

		stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);

		return;

	}

unlock:

	task_rq_unlock(rq, p, &flags);

	raw_spin_unlock_irqrestore(&p->pi_lock, flags);

}



#endif