sched: Delay task_contributes_to_load()

In prepratation of having to call task_contributes_to_load() without
holding rq->lock, we need to store the result until we do and can
update the rq accounting accordingly.

Reviewed-by: Frank 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: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110405152729.151523907@chello.nl

Author: Peter Zijlstra

include/linux/sched.h

@@ -1273,6 +1273,7 @@ struct task_struct {
 
 	/* Revert to default priority/policy when forking */
 	unsigned sched_reset_on_fork:1;
+	unsigned sched_contributes_to_load:1;
 
 	pid_t pid;
 	pid_t tgid;

kernel/sched.c

@@ -2519,18 +2519,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state,
 	if (unlikely(task_running(rq, p)))
 		goto out_activate;
 
-	/*
-	 * In order to handle concurrent wakeups and release the rq->lock
-	 * we put the task in TASK_WAKING state.
-	 *
-	 * First fix up the nr_uninterruptible count:
-	 */
-	if (task_contributes_to_load(p)) {
-		if (likely(cpu_online(orig_cpu)))
-			rq->nr_uninterruptible--;
-		else
-			this_rq()->nr_uninterruptible--;
-	}
+	p->sched_contributes_to_load = !!task_contributes_to_load(p);
 	p->state = TASK_WAKING;
 
 	if (p->sched_class->task_waking) {
@@ -2555,6 +2544,9 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state,
 	WARN_ON(task_cpu(p) != cpu);
 	WARN_ON(p->state != TASK_WAKING);
 
+	if (p->sched_contributes_to_load)
+		rq->nr_uninterruptible--;
+
 out_activate:
 #endif /* CONFIG_SMP */
 	ttwu_activate(rq, p, en_flags);