workqueue: wake up a worker when a rescuer is leaving a gcwq

After executing the matching works, a rescuer leaves the gcwq whether
there are more pending works or not.  This may decrease the
concurrency level to zero and stall execution until a new work item is
queued on the gcwq.

Make rescuer wake up a regular worker when it leaves a gcwq if there
are more works to execute, so that execution isn't stalled.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Ray Jui <rjui@broadcom.com>
Cc: stable@kernel.org

1 files changed, 9 insertions, 0 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 11869faa6819..90a17ca2ad0b 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2047,6 +2047,15 @@ repeat:
                                 move_linked_works(work, scheduled, &n);
 
                 process_scheduled_works(rescuer);
+
+                /*
+                 * Leave this gcwq.  If keep_working() is %true, notify a
+                 * regular worker; otherwise, we end up with 0 concurrency
+                 * and stalling the execution.
+                 */
+                if (keep_working(gcwq))
+                        wake_up_worker(gcwq);
+
                 spin_unlock_irq(&gcwq->lock);
         }