---

yaml
---
r: 158336
b: refs/heads/master
c: 3f029d3
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c3a2ae3d93c0f10d29c071f599764d00b8de00cb
+refs/heads/master: 3f029d3c6d62068d59301d90c18dbde8ee402107

trunk/include/linux/sched.h

@@ -1047,7 +1047,6 @@ struct sched_class {
 			      struct rq *busiest, struct sched_domain *sd,
 			      enum cpu_idle_type idle);
 	void (*pre_schedule) (struct rq *this_rq, struct task_struct *task);
-	int (*needs_post_schedule) (struct rq *this_rq);
 	void (*post_schedule) (struct rq *this_rq);
 	void (*task_wake_up) (struct rq *this_rq, struct task_struct *task);
 

trunk/kernel/sched.c

@@ -616,6 +616,7 @@ struct rq {
 
 	unsigned char idle_at_tick;
 	/* For active balancing */
+	int post_schedule;
 	int active_balance;
 	int push_cpu;
 	/* cpu of this runqueue: */
@@ -2839,17 +2840,11 @@ prepare_task_switch(struct rq *rq, struct task_struct *prev,
  * with the lock held can cause deadlocks; see schedule() for
  * details.)
  */
-static int finish_task_switch(struct rq *rq, struct task_struct *prev)
+static void finish_task_switch(struct rq *rq, struct task_struct *prev)
 	__releases(rq->lock)
 {
 	struct mm_struct *mm = rq->prev_mm;
 	long prev_state;
-	int post_schedule = 0;
-
-#ifdef CONFIG_SMP
-	if (current->sched_class->needs_post_schedule)
-		post_schedule = current->sched_class->needs_post_schedule(rq);
-#endif
 
 	rq->prev_mm = NULL;
 
@@ -2880,10 +2875,44 @@ static int finish_task_switch(struct rq *rq, struct task_struct *prev)
 		kprobe_flush_task(prev);
 		put_task_struct(prev);
 	}
+}
+
+#ifdef CONFIG_SMP
+
+/* assumes rq->lock is held */
+static inline void pre_schedule(struct rq *rq, struct task_struct *prev)
+{
+	if (prev->sched_class->pre_schedule)
+		prev->sched_class->pre_schedule(rq, prev);
+}
+
+/* rq->lock is NOT held, but preemption is disabled */
+static inline void post_schedule(struct rq *rq)
+{
+	if (rq->post_schedule) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&rq->lock, flags);
+		if (rq->curr->sched_class->post_schedule)
+			rq->curr->sched_class->post_schedule(rq);
+		spin_unlock_irqrestore(&rq->lock, flags);
+
+		rq->post_schedule = 0;
+	}
+}
+
+#else
 
-	return post_schedule;
+static inline void pre_schedule(struct rq *rq, struct task_struct *p)
+{
+}
+
+static inline void post_schedule(struct rq *rq)
+{
 }
 
+#endif
+
 /**
  * schedule_tail - first thing a freshly forked thread must call.
  * @prev: the thread we just switched away from.
@@ -2892,14 +2921,14 @@ asmlinkage void schedule_tail(struct task_struct *prev)
 	__releases(rq->lock)
 {
 	struct rq *rq = this_rq();
-	int post_schedule;
 
-	post_schedule = finish_task_switch(rq, prev);
+	finish_task_switch(rq, prev);
 
-#ifdef CONFIG_SMP
-	if (post_schedule)
-		current->sched_class->post_schedule(rq);
-#endif
+	/*
+	 * FIXME: do we need to worry about rq being invalidated by the
+	 * task_switch?
+	 */
+	post_schedule(rq);
 
 #ifdef __ARCH_WANT_UNLOCKED_CTXSW
 	/* In this case, finish_task_switch does not reenable preemption */
@@ -2913,7 +2942,7 @@ asmlinkage void schedule_tail(struct task_struct *prev)
  * context_switch - switch to the new MM and the new
  * thread's register state.
  */
-static inline int
+static inline void
 context_switch(struct rq *rq, struct task_struct *prev,
 	       struct task_struct *next)
 {
@@ -2960,7 +2989,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
 	 * CPUs since it called schedule(), thus the 'rq' on its stack
 	 * frame will be invalid.
 	 */
-	return finish_task_switch(this_rq(), prev);
+	finish_task_switch(this_rq(), prev);
 }
 
 /*
@@ -5371,7 +5400,6 @@ asmlinkage void __sched schedule(void)
 {
 	struct task_struct *prev, *next;
 	unsigned long *switch_count;
-	int post_schedule = 0;
 	struct rq *rq;
 	int cpu;
 
@@ -5403,10 +5431,7 @@ asmlinkage void __sched schedule(void)
 		switch_count = &prev->nvcsw;
 	}
 
-#ifdef CONFIG_SMP
-	if (prev->sched_class->pre_schedule)
-		prev->sched_class->pre_schedule(rq, prev);
-#endif
+	pre_schedule(rq, prev);
 
 	if (unlikely(!rq->nr_running))
 		idle_balance(cpu, rq);
@@ -5422,25 +5447,17 @@ asmlinkage void __sched schedule(void)
 		rq->curr = next;
 		++*switch_count;
 
-		post_schedule = context_switch(rq, prev, next); /* unlocks the rq */
+		context_switch(rq, prev, next); /* unlocks the rq */
 		/*
 		 * the context switch might have flipped the stack from under
 		 * us, hence refresh the local variables.
 		 */
 		cpu = smp_processor_id();
 		rq = cpu_rq(cpu);
-	} else {
-#ifdef CONFIG_SMP
-		if (current->sched_class->needs_post_schedule)
-			post_schedule = current->sched_class->needs_post_schedule(rq);
-#endif
+	} else
 		spin_unlock_irq(&rq->lock);
-	}
 
-#ifdef CONFIG_SMP
-	if (post_schedule)
-		current->sched_class->post_schedule(rq);
-#endif
+	post_schedule(rq);
 
 	if (unlikely(reacquire_kernel_lock(current) < 0))
 		goto need_resched_nonpreemptible;
@@ -9403,6 +9420,7 @@ void __init sched_init(void)
 #ifdef CONFIG_SMP
 		rq->sd = NULL;
 		rq->rd = NULL;
+		rq->post_schedule = 0;
 		rq->active_balance = 0;
 		rq->next_balance = jiffies;
 		rq->push_cpu = 0;

trunk/kernel/sched_rt.c

@@ -1056,6 +1056,11 @@ static struct task_struct *_pick_next_task_rt(struct rq *rq)
 	return p;
 }
 
+static inline int has_pushable_tasks(struct rq *rq)
+{
+	return !plist_head_empty(&rq->rt.pushable_tasks);
+}
+
 static struct task_struct *pick_next_task_rt(struct rq *rq)
 {
 	struct task_struct *p = _pick_next_task_rt(rq);
@@ -1064,6 +1069,12 @@ static struct task_struct *pick_next_task_rt(struct rq *rq)
 	if (p)
 		dequeue_pushable_task(rq, p);
 
+	/*
+	 * We detect this state here so that we can avoid taking the RQ
+	 * lock again later if there is no need to push
+	 */
+	rq->post_schedule = has_pushable_tasks(rq);
+
 	return p;
 }
 
@@ -1262,11 +1273,6 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
 	return lowest_rq;
 }
 
-static inline int has_pushable_tasks(struct rq *rq)
-{
-	return !plist_head_empty(&rq->rt.pushable_tasks);
-}
-
 static struct task_struct *pick_next_pushable_task(struct rq *rq)
 {
 	struct task_struct *p;
@@ -1466,23 +1472,9 @@ static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
 		pull_rt_task(rq);
 }
 
-/*
- * assumes rq->lock is held
- */
-static int needs_post_schedule_rt(struct rq *rq)
-{
-	return has_pushable_tasks(rq);
-}
-
 static void post_schedule_rt(struct rq *rq)
 {
-	/*
-	 * This is only called if needs_post_schedule_rt() indicates that
-	 * we need to push tasks away
-	 */
-	spin_lock_irq(&rq->lock);
 	push_rt_tasks(rq);
-	spin_unlock_irq(&rq->lock);
 }
 
 /*
@@ -1758,7 +1750,6 @@ static const struct sched_class rt_sched_class = {
 	.rq_online              = rq_online_rt,
 	.rq_offline             = rq_offline_rt,
 	.pre_schedule		= pre_schedule_rt,
-	.needs_post_schedule	= needs_post_schedule_rt,
 	.post_schedule		= post_schedule_rt,
 	.task_wake_up		= task_wake_up_rt,
 	.switched_from		= switched_from_rt,