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-rw-r--r--kernel/locking/rwsem-spinlock.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/locking/rwsem-spinlock.c b/kernel/locking/rwsem-spinlock.c
index 2555ae15ec14..3a5048572065 100644
--- a/kernel/locking/rwsem-spinlock.c
+++ b/kernel/locking/rwsem-spinlock.c
@@ -85,6 +85,13 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wakewrite)
list_del(&waiter->list);
tsk = waiter->task;
+ /*
+ * Make sure we do not wakeup the next reader before
+ * setting the nil condition to grant the next reader;
+ * otherwise we could miss the wakeup on the other
+ * side and end up sleeping again. See the pairing
+ * in rwsem_down_read_failed().
+ */
smp_mb();
waiter->task = NULL;
wake_up_process(tsk);