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Commit c05fbafb authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Restructure ttwu() some more 



Factor our helper functions to make the inner workings of try_to_wake_up()
more obvious, this also allows for adding remote queues.

Reviewed-by: default avatarFrank Rowand <frank.rowand@am.sony.com>
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>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110405152729.475848012@chello.nl
parent 23f41eeb

kernel/sched.c

+58 −33
Original line number Diff line number Diff line
@@ -2483,6 +2483,48 @@ ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) 
#endif

}



static void

ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags)

{

#ifdef CONFIG_SMP

	if (p->sched_contributes_to_load)

		rq->nr_uninterruptible--;

#endif



	ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING);

	ttwu_do_wakeup(rq, p, wake_flags);

}



/*

 * Called in case the task @p isn't fully descheduled from its runqueue,

 * in this case we must do a remote wakeup. Its a 'light' wakeup though,

 * since all we need to do is flip p->state to TASK_RUNNING, since

 * the task is still ->on_rq.

 */

static int ttwu_remote(struct task_struct *p, int wake_flags)

{

	struct rq *rq;

	int ret = 0;



	rq = __task_rq_lock(p);

	if (p->on_rq) {

		ttwu_do_wakeup(rq, p, wake_flags);

		ret = 1;

	}

	__task_rq_unlock(rq);



	return ret;

}



static void ttwu_queue(struct task_struct *p, int cpu)

{

	struct rq *rq = cpu_rq(cpu);



	raw_spin_lock(&rq->lock);

	ttwu_do_activate(rq, p, 0);

	raw_spin_unlock(&rq->lock);

}



/**

 * try_to_wake_up - wake up a thread

 * @p: the thread to be awakened
@@ -2501,27 +2543,25 @@ ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) 
static int

try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)

{

	int cpu, this_cpu, success = 0;

	unsigned long flags;

	struct rq *rq;



	this_cpu = get_cpu();

	int cpu, success = 0;



	smp_wmb();

	raw_spin_lock_irqsave(&p->pi_lock, flags);

	if (!(p->state & state))

		goto out;



	success = 1; /* we're going to change ->state */

	cpu = task_cpu(p);



	if (p->on_rq) {

		rq = __task_rq_lock(p);

		if (p->on_rq)

			goto out_running;

		__task_rq_unlock(rq);

	}

	if (p->on_rq && ttwu_remote(p, wake_flags))

		goto stat;



#ifdef CONFIG_SMP

	/*

	 * If the owning (remote) cpu is still in the middle of schedule() with

	 * this task as prev, wait until its done referencing the task.

	 */

	while (p->on_cpu) {

#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW

		/*
@@ -2530,8 +2570,10 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) 
		 * to spin on ->on_cpu if p is current, since that would

		 * deadlock.

		 */

		if (p == current)

			goto out_activate;

		if (p == current) {

			ttwu_queue(p, cpu);

			goto stat;

		}

#endif

		cpu_relax();

	}
@@ -2547,32 +2589,15 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) 
		p->sched_class->task_waking(p);



	cpu = select_task_rq(p, SD_BALANCE_WAKE, wake_flags);

#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW

out_activate:

#endif

#endif /* CONFIG_SMP */



	rq = cpu_rq(cpu);

	raw_spin_lock(&rq->lock);



#ifdef CONFIG_SMP

	if (cpu != task_cpu(p))

	if (task_cpu(p) != cpu)

		set_task_cpu(p, cpu);

#endif /* CONFIG_SMP */



	if (p->sched_contributes_to_load)

		rq->nr_uninterruptible--;

#endif



	ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING);

out_running:

	ttwu_do_wakeup(rq, p, wake_flags);

	success = 1;

	__task_rq_unlock(rq);



	ttwu_queue(p, cpu);

stat:

	ttwu_stat(p, cpu, wake_flags);

out:

	raw_spin_unlock_irqrestore(&p->pi_lock, flags);

	put_cpu();



	return success;

}