workqueue: Add pool_workqueue to pending_pwqs list when unplugging multiple inactive...

In unplug_oldest_pwq(), the first inactive work item on the
pool_workqueue is activated correctly. However, if multiple inactive
works exist on the same pool_workqueue, subsequent works fail to
activate because wq_node_nr_active.pending_pwqs is empty — the list
insertion is skipped when the pool_workqueue is plugged.

Fix this by checking for additional inactive works in
unplug_oldest_pwq() and updating wq_node_nr_active.pending_pwqs
accordingly.

Fixes: 4c065dbce1e8 ("workqueue: Enable unbound cpumask update on ordered workqueues")
Cc: stable@vger.kernel.org
Cc: Carlos Santa <carlos.santa@intel.com>
Cc: Ryan Neph <ryanneph@google.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Waiman Long <longman@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index eda7565..c6ea96d 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1849,8 +1849,20 @@ static void unplug_oldest_pwq(struct workqueue_struct *wq)
        raw_spin_lock_irq(&pwq->pool->lock);
        if (pwq->plugged) {
                pwq->plugged = false;
-               if (pwq_activate_first_inactive(pwq, true))
+               if (pwq_activate_first_inactive(pwq, true)) {
+                       /*
+                        * While plugged, queueing skips activation which
+                        * includes bumping the nr_active count and adding the
+                        * pwq to nna->pending_pwqs if the count can't be
+                        * obtained. We need to restore both for the pwq being
+                        * unplugged. The first call activates the first
+                        * inactive work item and the second, if there are more
+                        * inactive, puts the pwq on pending_pwqs.
+                        */
+                       pwq_activate_first_inactive(pwq, false);
+
                        kick_pool(pwq->pool);
+               }
        }
        raw_spin_unlock_irq(&pwq->pool->lock);
 }