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

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 11869faa6819767fba57f1e45789da7b56f15e74..90a17ca2ad0bf732d16137dc674f9488daaec647 100644 (file)
--- 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);
        }