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authorTejun Heo <tj@kernel.org>2012-08-22 00:18:24 +0400
committerTejun Heo <tj@kernel.org>2012-08-22 00:18:24 +0400
commite0aecdd874d78b7129a64b056c20e529e2c916df (patch)
tree0eacde209b1f46beb5293537c85ab8217c7023f4 /kernel/workqueue.c
parentf991b318cc6627a493b0d317a565bb7c3271f36b (diff)
downloadlinux-e0aecdd874d78b7129a64b056c20e529e2c916df.tar.xz
workqueue: use irqsafe timer for delayed_work
Up to now, for delayed_works, try_to_grab_pending() couldn't be used from IRQ handlers because IRQs may happen while delayed_work_timer_fn() is in progress leading to indefinite -EAGAIN. This patch makes delayed_work use the new TIMER_IRQSAFE flag for delayed_work->timer. This makes try_to_grab_pending() and thus mod_delayed_work_on() safe to call from IRQ handlers. Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r--kernel/workqueue.c20
1 files changed, 11 insertions, 9 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 85bd3409b9f5..b394df8beaee 100644
--- a/kernel/workqueue.c
+++ b/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,