[PATCH 05/27] sched: add wakeup/sleep sched_notifiers and allow NULL notifier ops

[Tejun Heo <tj@kernel.org>]

Add wakeup and sleep notifiers to sched_notifiers and allow omitting
some of the notifiers in the ops table.  These will be used by
concurrency managed workqueue.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@elte.hu>
---
 include/linux/sched.h |    6 ++++++
 kernel/sched.c        |   11 ++++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f327ac7..b3c1666 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1215,6 +1215,10 @@ struct sched_notifier;
 
 /**
  * sched_notifier_ops - notifiers called for scheduling events
+ * @wakeup: we're waking up
+ *    notifier: struct sched_notifier for the task being woken up
+ * @sleep: we're going to bed
+ *    notifier: struct sched_notifier for the task sleeping
  * @in: we're about to be rescheduled:
  *    notifier: struct sched_notifier for the task being scheduled
  *    cpu:  cpu we're scheduled on
@@ -1228,6 +1232,8 @@ struct sched_notifier;
  * and depended upon by its users.
  */
 struct sched_notifier_ops {
+	void (*wakeup)(struct sched_notifier *notifier);
+	void (*sleep)(struct sched_notifier *notifier);
 	void (*in)(struct sched_notifier *notifier, int cpu);
 	void (*out)(struct sched_notifier *notifier, struct task_struct *next);
 };
diff --git a/kernel/sched.c b/kernel/sched.c
index f44db0b..35af985 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1439,7 +1439,8 @@ static inline void cpuacct_update_stats(struct task_struct *tsk,
 	struct hlist_node *__pos;					\
 									\
 	hlist_for_each_entry(__sn, __pos, &(p)->sched_notifiers, link)	\
-		__sn->ops->callback(__sn , ##args);			\
+		if (__sn->ops->callback)				\
+			__sn->ops->callback(__sn , ##args);		\
 } while (0)
 
 /**
@@ -2410,6 +2411,8 @@ static inline void ttwu_post_activation(struct task_struct *p, struct rq *rq,
 		rq->idle_stamp = 0;
 	}
 #endif
+	if (success)
+		fire_sched_notifiers(p, wakeup);
 }
 
 /**
@@ -5448,10 +5451,12 @@ need_resched_nonpreemptible:
 	clear_tsk_need_resched(prev);
 
 	if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
-		if (unlikely(signal_pending_state(prev->state, prev)))
+		if (unlikely(signal_pending_state(prev->state, prev))) {
 			prev->state = TASK_RUNNING;
-		else
+		} else {
+			fire_sched_notifiers(prev, sleep);
 			deactivate_task(rq, prev, 1);
+		}
 		switch_count = &prev->nvcsw;
 	}
 
-- 
1.6.4.2