From a15b997362e501da1b29c203752d8e1c5e4ec1ee Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Thu, 26 May 2011 14:21:33 +0200
Subject: [PATCH] --- yaml --- r: 252683 b: refs/heads/master c:
 d6aa8f85f16379d42c147b22b59e33b67f9ff466 h: refs/heads/master i:   252681:
 c8bf90b0bb4cb3211886ed43cba69a61636edb54   252679:
 2e16037c3da85be94ea00901dfc621598be8eb67 v: v3

---
 [refs]               |  2 +-
 trunk/kernel/sched.c | 37 ++++++++++++++++++++++++++++---------
 2 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/[refs] b/[refs]
index 4cabe62bd987..f80385247b76 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: cd4ae6adf8b1c21d88e83ed56afeeef97b28f356
+refs/heads/master: d6aa8f85f16379d42c147b22b59e33b67f9ff466
diff --git a/trunk/kernel/sched.c b/trunk/kernel/sched.c
index 5e43e9dc65d1..a80ee911900e 100644
--- a/trunk/kernel/sched.c
+++ b/trunk/kernel/sched.c
@@ -2573,7 +2573,26 @@ static void ttwu_queue_remote(struct task_struct *p, int cpu)
 	if (!next)
 		smp_send_reschedule(cpu);
 }
-#endif
+
+#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
+static int ttwu_activate_remote(struct task_struct *p, int wake_flags)
+{
+	struct rq *rq;
+	int ret = 0;
+
+	rq = __task_rq_lock(p);
+	if (p->on_cpu) {
+		ttwu_activate(rq, p, ENQUEUE_WAKEUP);
+		ttwu_do_wakeup(rq, p, wake_flags);
+		ret = 1;
+	}
+	__task_rq_unlock(rq);
+
+	return ret;
+
+}
+#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
+#endif /* CONFIG_SMP */
 
 static void ttwu_queue(struct task_struct *p, int cpu)
 {
@@ -2631,17 +2650,17 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 	while (p->on_cpu) {
 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
 		/*
-		 * If called from interrupt context we could have landed in the
-		 * middle of schedule(), in this case we should take care not
-		 * to spin on ->on_cpu if p is current, since that would
-		 * deadlock.
+		 * In case the architecture enables interrupts in
+		 * context_switch(), we cannot busy wait, since that
+		 * would lead to deadlocks when an interrupt hits and
+		 * tries to wake up @prev. So bail and do a complete
+		 * remote wakeup.
 		 */
-		if (p == current) {
-			ttwu_queue(p, cpu);
+		if (ttwu_activate_remote(p, wake_flags))
 			goto stat;
-		}
-#endif
+#else
 		cpu_relax();
+#endif
 	}
 	/*
 	 * Pairs with the smp_wmb() in finish_lock_switch().