Merge remote branch 'workqueues/for-next'

1 files changed, 26 insertions, 1 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index dee48658805c..b156dd6c87f3 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -482,7 +482,8 @@ static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 	int active = 0;
 	struct wq_barrier barr;
 
-	WARN_ON(cwq->thread == current);
+	if (WARN_ON(cwq->thread == current))
+		return 1;
 
 	spin_lock_irq(&cwq->lock);
 	if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
@@ -845,6 +846,30 @@ int schedule_on_each_cpu(work_func_t func)
 	return 0;
 }
 
+/**
+ * flush_scheduled_work - ensure that any scheduled work has run to completion.
+ *
+ * Forces execution of the kernel-global workqueue and blocks until its
+ * completion.
+ *
+ * Think twice before calling this function!  It's very easy to get into
+ * trouble if you don't take great care.  Either of the following situations
+ * will lead to deadlock:
+ *
+ *	One of the work items currently on the workqueue needs to acquire
+ *	a lock held by your code or its caller.
+ *
+ *	Your code is running in the context of a work routine.
+ *
+ * They will be detected by lockdep when they occur, but the first might not
+ * occur very often.  It depends on what work items are on the workqueue and
+ * what locks they need, which you have no control over.
+ *
+ * In most situations flushing the entire workqueue is overkill; you merely
+ * need to know that a particular work item isn't queued and isn't running.
+ * In such cases you should use cancel_delayed_work_sync() or
+ * cancel_work_sync() instead.
+ */
 void flush_scheduled_work(void)
 {
 	flush_workqueue(keventd_wq);