From d98a33903f1037b87d113b8c5b12df0ccbf58bbb Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Fri, 3 Aug 2012 10:30:46 -0700
Subject: [PATCH] --- yaml --- r: 327159 b: refs/heads/master c:
 36e227d242f9ec7cb4a8e968561b3b26e3d8b5d1 h: refs/heads/master i:   327157:
 f2e89e181d71e35e621d40ec185689347efe5dd9   327155:
 d0602743780c046562d8ca19280c52f4e59f0906   327151:
 72b80f803e60520950ef786d5053467cdc676a3b v: v3

---
 [refs]                   |  2 +-
 trunk/kernel/workqueue.c | 47 +++++++++++++++++++++++++++-------------
 2 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/[refs] b/[refs]
index 12e062d10ca5..e8a443840a4f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7beb2edf44b4dea820c733046ad7666d092bb4b6
+refs/heads/master: 36e227d242f9ec7cb4a8e968561b3b26e3d8b5d1
diff --git a/trunk/kernel/workqueue.c b/trunk/kernel/workqueue.c
index d7f1b7e2bbaa..4b3663b1c677 100644
--- a/trunk/kernel/workqueue.c
+++ b/trunk/kernel/workqueue.c
@@ -1004,15 +1004,33 @@ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
 		complete(&cwq->wq->first_flusher->done);
 }
 
-/*
- * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
- * so this work can't be re-armed in any way.
+/**
+ * try_to_grab_pending - steal work item from worklist
+ * @work: work item to steal
+ * @is_dwork: @work is a delayed_work
+ *
+ * Try to grab PENDING bit of @work.  This function can handle @work in any
+ * stable state - idle, on timer or on worklist.  Return values are
+ *
+ *  1		if @work was pending and we successfully stole PENDING
+ *  0		if @work was idle and we claimed PENDING
+ *  -EAGAIN	if PENDING couldn't be grabbed at the moment, safe to busy-retry
+ *
+ * On >= 0 return, the caller owns @work's PENDING bit.
  */
-static int try_to_grab_pending(struct work_struct *work)
+static int try_to_grab_pending(struct work_struct *work, bool is_dwork)
 {
 	struct global_cwq *gcwq;
-	int ret = -1;
 
+	/* try to steal the timer if it exists */
+	if (is_dwork) {
+		struct delayed_work *dwork = to_delayed_work(work);
+
+		if (likely(del_timer(&dwork->timer)))
+			return 1;
+	}
+
+	/* try to claim PENDING the normal way */
 	if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
 		return 0;
 
@@ -1022,7 +1040,7 @@ static int try_to_grab_pending(struct work_struct *work)
 	 */
 	gcwq = get_work_gcwq(work);
 	if (!gcwq)
-		return ret;
+		return -EAGAIN;
 
 	spin_lock_irq(&gcwq->lock);
 	if (!list_empty(&work->entry)) {
@@ -1038,12 +1056,14 @@ static int try_to_grab_pending(struct work_struct *work)
 			cwq_dec_nr_in_flight(get_work_cwq(work),
 				get_work_color(work),
 				*work_data_bits(work) & WORK_STRUCT_DELAYED);
-			ret = 1;
+
+			spin_unlock_irq(&gcwq->lock);
+			return 1;
 		}
 	}
 	spin_unlock_irq(&gcwq->lock);
 
-	return ret;
+	return -EAGAIN;
 }
 
 /**
@@ -2817,15 +2837,12 @@ bool flush_work_sync(struct work_struct *work)
 }
 EXPORT_SYMBOL_GPL(flush_work_sync);
 
-static bool __cancel_work_timer(struct work_struct *work,
-				struct timer_list* timer)
+static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
 {
 	int ret;
 
 	do {
-		ret = (timer && likely(del_timer(timer)));
-		if (!ret)
-			ret = try_to_grab_pending(work);
+		ret = try_to_grab_pending(work, is_dwork);
 		wait_on_work(work);
 	} while (unlikely(ret < 0));
 
@@ -2853,7 +2870,7 @@ static bool __cancel_work_timer(struct work_struct *work,
  */
 bool cancel_work_sync(struct work_struct *work)
 {
-	return __cancel_work_timer(work, NULL);
+	return __cancel_work_timer(work, false);
 }
 EXPORT_SYMBOL_GPL(cancel_work_sync);
 
@@ -2914,7 +2931,7 @@ EXPORT_SYMBOL(flush_delayed_work_sync);
  */
 bool cancel_delayed_work_sync(struct delayed_work *dwork)
 {
-	return __cancel_work_timer(&dwork->work, &dwork->timer);
+	return __cancel_work_timer(&dwork->work, true);
 }
 EXPORT_SYMBOL(cancel_delayed_work_sync);