locking/rwsem: Reinit wake_q after use

In __rwsem_down_write_failed_common(), the same wake_q variable name
is defined twice, with the inner wake_q hiding the one in outer scope.
We can either use different names for the two wake_q's.

Even better, we can use the same wake_q twice, if necessary.

To enable the latter change, we need to define a new helper function
wake_q_init() to enable reinitalization of wake_q after use.

Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1485052415-9611-1-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index a3a381aee24b..2ad8d8dc3bb1 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -502,8 +502,6 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
                  * wake any read locks that were queued ahead of us.
                  */
                 if (count > RWSEM_WAITING_BIAS) {
-                        DEFINE_WAKE_Q(wake_q);
-
                         __rwsem_mark_wake(sem, RWSEM_WAKE_READERS, &wake_q);
                         /*
                          * The wakeup is normally called _after_ the wait_lock
@@ -513,6 +511,11 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
                          * for attempting rwsem_try_write_lock().
                          */
                         wake_up_q(&wake_q);
+
+                        /*
+                         * Reinitialize wake_q after use.
+                         */
+                        wake_q_init(&wake_q);
                 }
 
         } else