[PATCH 07/15] workqueue: fix zero @delay handling of queue_delayed_work_on()

[Tejun Heo <tj@kernel.org>]

If @delay is zero and the dealyed_work is idle, queue_delayed_work()
queues it for immediate execution; however, queue_delayed_work_on()
lacks this logic and always goes through timer regardless of @delay.

This patch moves 0 @delay handling logic from queue_delayed_work() to
queue_delayed_work_on() so that both functions behave the same.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/workqueue.c |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 4beb9bf..e3383e8 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1123,7 +1123,9 @@ EXPORT_SYMBOL_GPL(delayed_work_timer_fn);
  * @dwork: work to queue
  * @delay: number of jiffies to wait before queueing
  *
- * Returns %false if @work was already on a queue, %true otherwise.
+ * Returns %false if @work was already on a queue, %true otherwise.  If
+ * @delay is zero and @dwork is idle, it will be scheduled for immediate
+ * execution.
  */
 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 			   struct delayed_work *dwork, unsigned long delay)
@@ -1132,6 +1134,9 @@ bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 	struct work_struct *work = &dwork->work;
 	bool ret = false;
 
+	if (!delay)
+		return queue_work_on(cpu, wq, &dwork->work);
+
 	/*
 	 * We shouldn't get preempted between claiming PENDING and adding
 	 * timer.  Read the comment in __queue_work() for details.
@@ -1185,14 +1190,11 @@ EXPORT_SYMBOL_GPL(queue_delayed_work_on);
  * @dwork: delayable work to queue
  * @delay: number of jiffies to wait before queueing
  *
- * Returns %false if @work was already on a queue, %true otherwise.
+ * Equivalent to queue_delayed_work_on() but tries to use the local CPU.
  */
 bool queue_delayed_work(struct workqueue_struct *wq,
 			struct delayed_work *dwork, unsigned long delay)
 {
-	if (delay == 0)
-		return queue_work(wq, &dwork->work);
-
 	return queue_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
 }
 EXPORT_SYMBOL_GPL(queue_delayed_work);
-- 
1.7.7.3