1 files changed, 63 insertions, 4 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 90db1bd1a97..8ee6ec82f88 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -661,7 +661,7 @@ void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
 {
 	struct worker *worker = kthread_data(task);
 
-	if (likely(!(worker->flags & WORKER_NOT_RUNNING)))
+	if (!(worker->flags & WORKER_NOT_RUNNING))
 		atomic_inc(get_gcwq_nr_running(cpu));
 }
 
@@ -687,7 +687,7 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task,
 	struct global_cwq *gcwq = get_gcwq(cpu);
 	atomic_t *nr_running = get_gcwq_nr_running(cpu);
 
-	if (unlikely(worker->flags & WORKER_NOT_RUNNING))
+	if (worker->flags & WORKER_NOT_RUNNING)
 		return NULL;
 
 	/* this can only happen on the local cpu */
@@ -932,6 +932,38 @@ static void insert_work(struct cpu_workqueue_struct *cwq,
 		wake_up_worker(gcwq);
 }
 
+/*
+ * Test whether @work is being queued from another work executing on the
+ * same workqueue.  This is rather expensive and should only be used from
+ * cold paths.
+ */
+static bool is_chained_work(struct workqueue_struct *wq)
+{
+	unsigned long flags;
+	unsigned int cpu;
+
+	for_each_gcwq_cpu(cpu) {
+		struct global_cwq *gcwq = get_gcwq(cpu);
+		struct worker *worker;
+		struct hlist_node *pos;
+		int i;
+
+		spin_lock_irqsave(&gcwq->lock, flags);
+		for_each_busy_worker(worker, i, pos, gcwq) {
+			if (worker->task != current)
+				continue;
+			spin_unlock_irqrestore(&gcwq->lock, flags);
+			/*
+			 * I'm @worker, no locking necessary.  See if @work
+			 * is headed to the same workqueue.
+			 */
+			return worker->current_cwq->wq == wq;
+		}
+		spin_unlock_irqrestore(&gcwq->lock, flags);
+	}
+	return false;
+}
+
 static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 			 struct work_struct *work)
 {
@@ -943,7 +975,9 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 
 	debug_work_activate(work);
 
-	if (WARN_ON_ONCE(wq->flags & WQ_DYING))
+	/* if dying, only works from the same workqueue are allowed */
+	if (unlikely(wq->flags & WQ_DYING) &&
+	    WARN_ON_ONCE(!is_chained_work(wq)))
 		return;
 
 	/* determine gcwq to use */
@@ -2936,11 +2970,35 @@ EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
  */
 void destroy_workqueue(struct workqueue_struct *wq)
 {
+	unsigned int flush_cnt = 0;
 	unsigned int cpu;
 
+	/*
+	 * Mark @wq dying and drain all pending works.  Once WQ_DYING is
+	 * set, only chain queueing is allowed.  IOW, only currently
+	 * pending or running work items on @wq can queue further work
+	 * items on it.  @wq is flushed repeatedly until it becomes empty.
+	 * The number of flushing is detemined by the depth of chaining and
+	 * should be relatively short.  Whine if it takes too long.
+	 */
 	wq->flags |= WQ_DYING;
+reflush:
 	flush_workqueue(wq);
 
+	for_each_cwq_cpu(cpu, wq) {
+		struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+
+		if (!cwq->nr_active && list_empty(&cwq->delayed_works))
+			continue;
+
+		if (++flush_cnt == 10 ||
+		    (flush_cnt % 100 == 0 && flush_cnt <= 1000))
+			printk(KERN_WARNING "workqueue %s: flush on "
+			       "destruction isn't complete after %u tries\n",
+			       wq->name, flush_cnt);
+		goto reflush;
+	}
+
 	/*
 	 * wq list is used to freeze wq, remove from list after
 	 * flushing is complete in case freeze races us.
@@ -3692,7 +3750,8 @@ static int __init init_workqueues(void)
 	system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
 	system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
 					    WQ_UNBOUND_MAX_ACTIVE);
-	BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq);
+	BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
+	       !system_unbound_wq);
 	return 0;
 }
 early_initcall(init_workqueues);