Merge branch 'next' into for-linus

Prepare first round of input updates for 3.20.

1 files changed, 27 insertions, 8 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 5dbe22aa3efd..6202b08f1933 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1804,8 +1804,8 @@ static void pool_mayday_timeout(unsigned long __pool)
         struct worker_pool *pool = (void *)__pool;
         struct work_struct *work;
 
-        spin_lock_irq(&wq_mayday_lock);         /* for wq->maydays */
-        spin_lock(&pool->lock);
+        spin_lock_irq(&pool->lock);
+        spin_lock(&wq_mayday_lock);             /* for wq->maydays */
 
         if (need_to_create_worker(pool)) {
                 /*
@@ -1818,8 +1818,8 @@ static void pool_mayday_timeout(unsigned long __pool)
                         send_mayday(work);
         }
 
-        spin_unlock(&pool->lock);
-        spin_unlock_irq(&wq_mayday_lock);
+        spin_unlock(&wq_mayday_lock);
+        spin_unlock_irq(&pool->lock);
 
         mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
 }
@@ -2043,9 +2043,10 @@ __acquires(&pool->lock)
          * kernels, where a requeueing work item waiting for something to
          * happen could deadlock with stop_machine as such work item could
          * indefinitely requeue itself while all other CPUs are trapped in
-         * stop_machine.
+         * stop_machine. At the same time, report a quiescent RCU state so
+         * the same condition doesn't freeze RCU.
          */
-        cond_resched();
+        cond_resched_rcu_qs();
 
         spin_lock_irq(&pool->lock);
 
@@ -2247,12 +2248,30 @@ repeat:
                  * Slurp in all works issued via this workqueue and
                  * process'em.
                  */
-                WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
+                WARN_ON_ONCE(!list_empty(scheduled));
                 list_for_each_entry_safe(work, n, &pool->worklist, entry)
                         if (get_work_pwq(work) == pwq)
                                 move_linked_works(work, scheduled, &n);
 
-                process_scheduled_works(rescuer);
+                if (!list_empty(scheduled)) {
+                        process_scheduled_works(rescuer);
+
+                        /*
+                         * The above execution of rescued work items could
+                         * have created more to rescue through
+                         * pwq_activate_first_delayed() or chained
+                         * queueing.  Let's put @pwq back on mayday list so
+                         * that such back-to-back work items, which may be
+                         * being used to relieve memory pressure, don't
+                         * incur MAYDAY_INTERVAL delay inbetween.
+                         */
+                        if (need_to_create_worker(pool)) {
+                                spin_lock(&wq_mayday_lock);
+                                get_pwq(pwq);
+                                list_move_tail(&pwq->mayday_node, &wq->maydays);
+                                spin_unlock(&wq_mayday_lock);
+                        }
+                }
 
                 /*
                  * Put the reference grabbed by send_mayday().  @pool won't