[RFC][PATCH 17/17] sched: Sort hotplug vs ttwu queueing

[Peter Zijlstra]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 kernel/sched.c |   20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -2470,15 +2470,15 @@ static int ttwu_remote(struct task_struc
 	return ret;
 }
 
-void sched_ttwu_pending(void)
+static void __sched_ttwu_pending(struct rq *rq)
 {
 #ifdef CONFIG_SMP
-	struct rq *rq = this_rq();
 	struct task_struct *list = xchg(&rq->wake_list, NULL);
 
 	if (!list)
 		return;
 
+	rq = this_rq(); /* always enqueue locally */
 	raw_spin_lock(&rq->lock);
 
 	while (list) {
@@ -2491,6 +2491,11 @@ void sched_ttwu_pending(void)
 #endif
 }
 
+void sched_ttwu_pending(void)
+{
+	__sched_ttwu_pending(this_rq());
+}
+
 #ifdef CONFIG_SMP
 static void ttwu_queue_remote(struct task_struct *p, int cpu)
 {
@@ -6162,6 +6167,17 @@ migration_call(struct notifier_block *nf
 		migrate_nr_uninterruptible(rq);
 		calc_global_load_remove(rq);
 		break;
+
+	case CPU_DEAD:
+		/*
+		 * Queue any possible remaining pending wakeups on this cpu.
+		 * Load-balancing will sort it out eventually.
+		 */
+		local_irq_save(flags);
+		__sched_ttwu_pending(cpu_rq(cpu));
+		local_irq_restore(flags);
+		break;
+
 #endif
 	}
 	return NOTIFY_OK;


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