From 583aa2e7f9175cdee549bebb150e0625414f6a47 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Tue, 21 Aug 2012 13:18:24 -0700
Subject: [PATCH] --- yaml --- r: 327181 b: refs/heads/master c:
 e0aecdd874d78b7129a64b056c20e529e2c916df h: refs/heads/master i:   327179:
 f4a6e99550f45b2c99d54b4c5e97042864d2fafd v: v3

---
 [refs]                          |  2 +-
 trunk/include/linux/workqueue.h |  8 +++++---
 trunk/kernel/workqueue.c        | 20 +++++++++++---------
 3 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/[refs] b/[refs]
index 7f301717d6fb..057085bd9d86 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: f991b318cc6627a493b0d317a565bb7c3271f36b
+refs/heads/master: e0aecdd874d78b7129a64b056c20e529e2c916df
diff --git a/trunk/include/linux/workqueue.h b/trunk/include/linux/workqueue.h
index e84ebb69607d..d86b320319e0 100644
--- a/trunk/include/linux/workqueue.h
+++ b/trunk/include/linux/workqueue.h
@@ -136,7 +136,8 @@ struct execute_work {
 #define __DELAYED_WORK_INITIALIZER(n, f, tflags) {			\
 	.work = __WORK_INITIALIZER((n).work, (f)),			\
 	.timer = __TIMER_INITIALIZER(delayed_work_timer_fn,		\
-			0, (unsigned long)&(n), (tflags)),		\
+				     0, (unsigned long)&(n),		\
+				     (tflags) | TIMER_IRQSAFE),		\
 	}
 
 #define DECLARE_WORK(n, f)						\
@@ -214,7 +215,8 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
 	do {								\
 		INIT_WORK(&(_work)->work, (_func));			\
 		__setup_timer(&(_work)->timer, delayed_work_timer_fn,	\
-			      (unsigned long)(_work), (_tflags));	\
+			      (unsigned long)(_work),			\
+			      (_tflags) | TIMER_IRQSAFE);		\
 	} while (0)
 
 #define __INIT_DELAYED_WORK_ONSTACK(_work, _func, _tflags)		\
@@ -223,7 +225,7 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
 		__setup_timer_on_stack(&(_work)->timer,			\
 				       delayed_work_timer_fn,		\
 				       (unsigned long)(_work),		\
-				       (_tflags));			\
+				       (_tflags) | TIMER_IRQSAFE);	\
 	} while (0)
 
 #define INIT_DELAYED_WORK(_work, _func)					\
diff --git a/trunk/kernel/workqueue.c b/trunk/kernel/workqueue.c
index 85bd3409b9f5..b394df8beaee 100644
--- a/trunk/kernel/workqueue.c
+++ b/trunk/kernel/workqueue.c
@@ -1048,16 +1048,14 @@ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
  *		for arbitrarily long
  *
  * On >= 0 return, the caller owns @work's PENDING bit.  To avoid getting
- * preempted while holding PENDING and @work off queue, preemption must be
- * disabled on entry.  This ensures that we don't return -EAGAIN while
- * another task is preempted in this function.
+ * interrupted while holding PENDING and @work off queue, irq must be
+ * disabled on entry.  This, combined with delayed_work->timer being
+ * irqsafe, ensures that we return -EAGAIN for finite short period of time.
  *
  * On successful return, >= 0, irq is disabled and the caller is
  * responsible for releasing it using local_irq_restore(*@flags).
  *
- * This function is safe to call from any context other than IRQ handler.
- * An IRQ handler may run on top of delayed_work_timer_fn() which can make
- * this function return -EAGAIN perpetually.
+ * This function is safe to call from any context including IRQ handler.
  */
 static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
 			       unsigned long *flags)
@@ -1072,6 +1070,11 @@ static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
 	if (is_dwork) {
 		struct delayed_work *dwork = to_delayed_work(work);
 
+		/*
+		 * dwork->timer is irqsafe.  If del_timer() fails, it's
+		 * guaranteed that the timer is not queued anywhere and not
+		 * running on the local CPU.
+		 */
 		if (likely(del_timer(&dwork->timer)))
 			return 1;
 	}
@@ -1327,9 +1330,8 @@ void delayed_work_timer_fn(unsigned long __data)
 	struct delayed_work *dwork = (struct delayed_work *)__data;
 	struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
 
-	local_irq_disable();
+	/* should have been called from irqsafe timer with irq already off */
 	__queue_work(dwork->cpu, cwq->wq, &dwork->work);
-	local_irq_enable();
 }
 EXPORT_SYMBOL_GPL(delayed_work_timer_fn);
 
@@ -1444,7 +1446,7 @@ EXPORT_SYMBOL_GPL(queue_delayed_work);
  * Returns %false if @dwork was idle and queued, %true if @dwork was
  * pending and its timer was modified.
  *
- * This function is safe to call from any context other than IRQ handler.
+ * This function is safe to call from any context including IRQ handler.
  * See try_to_grab_pending() for details.
  */
 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,