Merge branches 'pm-core', 'pm-qos', 'pm-domains' and 'pm-opp'

[linux.git] / kernel / rcu / srcu.c

diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index 665bc9951523d46b972545e7672599be7322b1f1..e773129c8b08d29d0ce81cbdbc195bed905b2562 100644 (file)
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -320,7 +320,16 @@ static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount)
  */
 static void srcu_flip(struct srcu_struct *sp)
 {
-       sp->completed++;
+       WRITE_ONCE(sp->completed, sp->completed + 1);
+
+       /*
+        * Ensure that if the updater misses an __srcu_read_unlock()
+        * increment, that task's next __srcu_read_lock() will see the
+        * above counter update.  Note that both this memory barrier
+        * and the one in srcu_readers_active_idx_check() provide the
+        * guarantee for __srcu_read_lock().
+        */
+       smp_mb(); /* D */  /* Pairs with C. */
 }
 
 /*