[RFC][PATCH 09/18] sched: Delay task_contributes_to_load()

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

[-- Attachment #1: sched-ttwu-contribute-to-load.patch --]
[-- Type: text/plain, Size: 1771 bytes --]

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.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/sched.h |    1 +
 kernel/sched.c        |   16 ++++------------
 2 files changed, 5 insertions(+), 12 deletions(-)

Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -1264,6 +1264,7 @@ 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;
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -2467,18 +2467,7 @@ static int try_to_wake_up(struct task_st
 	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) {
@@ -2503,6 +2492,9 @@ static int try_to_wake_up(struct task_st
 	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 */
 	activate_task(rq, p, en_flags);