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Commit 7608dec2 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Drop the rq argument to sched_class::select_task_rq() 



In preparation of calling select_task_rq() without rq->lock held, drop
the dependency on the rq argument.

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/20110405152729.031077745@chello.nl


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 013fdb80

include/linux/sched.h

+1 −2
Original line number Diff line number Diff line
@@ -1067,8 +1067,7 @@ struct sched_class { 
	void (*put_prev_task) (struct rq *rq, struct task_struct *p);



#ifdef CONFIG_SMP

	int  (*select_task_rq)(struct rq *rq, struct task_struct *p,

			       int sd_flag, int flags);

	int  (*select_task_rq)(struct task_struct *p, int sd_flag, int flags);



	void (*pre_schedule) (struct rq *this_rq, struct task_struct *task);

	void (*post_schedule) (struct rq *this_rq);

kernel/sched.c

+11 −9
Original line number Diff line number Diff line
@@ -2195,13 +2195,15 @@ static int migration_cpu_stop(void *data); 
 * The task's runqueue lock must be held.

 * Returns true if you have to wait for migration thread.

 */

static bool migrate_task(struct task_struct *p, struct rq *rq)

static bool need_migrate_task(struct task_struct *p)

{

	/*

	 * If the task is not on a runqueue (and not running), then

	 * the next wake-up will properly place the task.

	 */

	return p->on_rq || task_running(rq, p);

	bool running = p->on_rq || p->on_cpu;

	smp_rmb(); /* finish_lock_switch() */

	return running;

}



/*
@@ -2376,9 +2378,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p) 
 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.

 */

static inline

int select_task_rq(struct rq *rq, struct task_struct *p, int sd_flags, int wake_flags)

int select_task_rq(struct task_struct *p, int sd_flags, int wake_flags)

{

	int cpu = p->sched_class->select_task_rq(rq, p, sd_flags, wake_flags);

	int cpu = p->sched_class->select_task_rq(p, sd_flags, wake_flags);



	/*

	 * In order not to call set_task_cpu() on a blocking task we need
@@ -2533,7 +2535,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, 
		en_flags |= ENQUEUE_WAKING;

	}



	cpu = select_task_rq(rq, p, SD_BALANCE_WAKE, wake_flags);

	cpu = select_task_rq(p, SD_BALANCE_WAKE, wake_flags);

	if (cpu != orig_cpu)

		set_task_cpu(p, cpu);

	__task_rq_unlock(rq);
@@ -2744,7 +2746,7 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags) 
	 * We set TASK_WAKING so that select_task_rq() can drop rq->lock

	 * without people poking at ->cpus_allowed.

	 */

	cpu = select_task_rq(rq, p, SD_BALANCE_FORK, 0);

	cpu = select_task_rq(p, SD_BALANCE_FORK, 0);

	set_task_cpu(p, cpu);



	p->state = TASK_RUNNING;
@@ -3474,7 +3476,7 @@ void sched_exec(void) 
	int dest_cpu;



	rq = task_rq_lock(p, &flags);

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

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

	if (dest_cpu == smp_processor_id())

		goto unlock;
@@ -3482,7 +3484,7 @@ void sched_exec(void) 
	 * select_task_rq() can race against ->cpus_allowed

	 */

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

	    likely(cpu_active(dest_cpu)) && migrate_task(p, rq)) {

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

		struct migration_arg arg = { p, dest_cpu };



		task_rq_unlock(rq, &flags);
@@ -5911,7 +5913,7 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) 
		goto out;



	dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);

	if (migrate_task(p, rq)) {

	if (need_migrate_task(p)) {

		struct migration_arg arg = { p, dest_cpu };

		/* Need help from migration thread: drop lock and wait. */

		__task_rq_unlock(rq);

kernel/sched_fair.c

+1 −1
Original line number Diff line number Diff line
@@ -1657,7 +1657,7 @@ static int select_idle_sibling(struct task_struct *p, int target) 
 * preempt must be disabled.

 */

static int

select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_flags)

select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)

{

	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;

	int cpu = smp_processor_id();

kernel/sched_idletask.c

+1 −1
Original line number Diff line number Diff line
@@ -7,7 +7,7 @@ 


#ifdef CONFIG_SMP

static int

select_task_rq_idle(struct rq *rq, struct task_struct *p, int sd_flag, int flags)

select_task_rq_idle(struct task_struct *p, int sd_flag, int flags)

{

	return task_cpu(p); /* IDLE tasks as never migrated */

}

kernel/sched_rt.c

+26 −12
Original line number Diff line number Diff line
@@ -977,13 +977,23 @@ static void yield_task_rt(struct rq *rq) 
static int find_lowest_rq(struct task_struct *task);



static int

select_task_rq_rt(struct rq *rq, struct task_struct *p, int sd_flag, int flags)

select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)

{

	struct task_struct *curr;

	struct rq *rq;

	int cpu;



	if (sd_flag != SD_BALANCE_WAKE)

		return smp_processor_id();



	cpu = task_cpu(p);

	rq = cpu_rq(cpu);



	rcu_read_lock();

	curr = ACCESS_ONCE(rq->curr); /* unlocked access */



	/*

	 * If the current task is an RT task, then

	 * If the current task on @p's runqueue is an RT task, then

	 * try to see if we can wake this RT task up on another

	 * runqueue. Otherwise simply start this RT task

	 * on its current runqueue.
@@ -997,21 +1007,25 @@ select_task_rq_rt(struct rq *rq, struct task_struct *p, int sd_flag, int flags) 
	 * lock?

	 *

	 * For equal prio tasks, we just let the scheduler sort it out.

	 *

	 * Otherwise, just let it ride on the affined RQ and the

	 * post-schedule router will push the preempted task away

	 *

	 * This test is optimistic, if we get it wrong the load-balancer

	 * will have to sort it out.

	 */

	if (unlikely(rt_task(rq->curr)) &&

	    (rq->curr->rt.nr_cpus_allowed < 2 ||

	     rq->curr->prio < p->prio) &&

	if (curr && unlikely(rt_task(curr)) &&

	    (curr->rt.nr_cpus_allowed < 2 ||

	     curr->prio < p->prio) &&

	    (p->rt.nr_cpus_allowed > 1)) {

		int cpu = find_lowest_rq(p);

		int target = find_lowest_rq(p);



		return (cpu == -1) ? task_cpu(p) : cpu;

		if (target != -1)

			cpu = target;

	}

	rcu_read_unlock();



	/*

	 * Otherwise, just let it ride on the affined RQ and the

	 * post-schedule router will push the preempted task away

	 */

	return task_cpu(p);

	return cpu;

}



static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)