1 files changed, 59 insertions, 1 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e785b0f2aea5..8ee6ec82f88a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -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.