From 7b5dbaed29e5414133560e678df26c954221f5a4 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 13 Aug 2012 17:08:19 -0700
Subject: [PATCH] --- yaml --- r: 327164 b: refs/heads/master c:
 23657bb192f14b789e4c478def8f11ecc95b4f6c h: refs/heads/master v: v3

---
 [refs]                   |  2 +-
 trunk/kernel/workqueue.c | 19 ++++++++++++-------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/[refs] b/[refs]
index 1cb020abe06a..dae9315e663e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 1265057fa02c7bed3b6d9ddc8a2048065a370364
+refs/heads/master: 23657bb192f14b789e4c478def8f11ecc95b4f6c
diff --git a/trunk/kernel/workqueue.c b/trunk/kernel/workqueue.c
index 11723c5b2b20..4fef9527a620 100644
--- a/trunk/kernel/workqueue.c
+++ b/trunk/kernel/workqueue.c
@@ -570,11 +570,19 @@ static void set_work_cwq(struct work_struct *work,
 static void set_work_cpu_and_clear_pending(struct work_struct *work,
 					   unsigned int cpu)
 {
+	/*
+	 * The following wmb is paired with the implied mb in
+	 * test_and_set_bit(PENDING) and ensures all updates to @work made
+	 * here are visible to and precede any updates by the next PENDING
+	 * owner.
+	 */
+	smp_wmb();
 	set_work_data(work, (unsigned long)cpu << WORK_OFFQ_CPU_SHIFT, 0);
 }
 
 static void clear_work_data(struct work_struct *work)
 {
+	smp_wmb();	/* see set_work_cpu_and_clear_pending() */
 	set_work_data(work, WORK_STRUCT_NO_CPU, 0);
 }
 
@@ -2182,14 +2190,11 @@ __acquires(&gcwq->lock)
 		wake_up_worker(pool);
 
 	/*
-	 * Record the last CPU and clear PENDING.  The following wmb is
-	 * paired with the implied mb in test_and_set_bit(PENDING) and
-	 * ensures all updates to @work made here are visible to and
-	 * precede any updates by the next PENDING owner.  Also, clear
-	 * PENDING inside @gcwq->lock so that PENDING and queued state
-	 * changes happen together while IRQ is disabled.
+	 * Record the last CPU and clear PENDING which should be the last
+	 * update to @work.  Also, do this inside @gcwq->lock so that
+	 * PENDING and queued state changes happen together while IRQ is
+	 * disabled.
 	 */
-	smp_wmb();
 	set_work_cpu_and_clear_pending(work, gcwq->cpu);
 
 	spin_unlock_irq(&gcwq->lock);