1 files changed, 12 insertions, 0 deletions

diff --git a/kernel/padata.c b/kernel/padata.c
index 2d2fddbb7a4c..15a8ad63f4ff 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -267,7 +267,12 @@ static void padata_reorder(struct parallel_data *pd)
          * The next object that needs serialization might have arrived to
          * the reorder queues in the meantime, we will be called again
          * from the timer function if no one else cares for it.
+         *
+         * Ensure reorder_objects is read after pd->lock is dropped so we see
+         * an increment from another task in padata_do_serial.  Pairs with
+         * smp_mb__after_atomic in padata_do_serial.
          */
+        smp_mb();
         if (atomic_read(&pd->reorder_objects)
                         && !(pinst->flags & PADATA_RESET))
                 mod_timer(&pd->timer, jiffies + HZ);
@@ -387,6 +392,13 @@ void padata_do_serial(struct padata_priv *padata)
         list_add_tail(&padata->list, &pqueue->reorder.list);
         spin_unlock(&pqueue->reorder.lock);
 
+        /*
+         * Ensure the atomic_inc of reorder_objects above is ordered correctly
+         * with the trylock of pd->lock in padata_reorder.  Pairs with smp_mb
+         * in padata_reorder.
+         */
+        smp_mb__after_atomic();
+
         put_cpu();
 
         /* If we're running on the wrong CPU, call padata_reorder() via a