Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fixes from Thomas Gleixner:
 "A small series of fixes which all address possible missed wakeups:

   - Document and fix the wakeup ordering of wake_q

   - Add the missing barrier in rcuwait_wake_up(), which was documented
     in the comment but missing in the code

   - Fix the possible missed wakeups in the rwsem and futex code"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/rwsem: Fix (possible) missed wakeup
  futex: Fix (possible) missed wakeup
  sched/wake_q: Fix wakeup ordering for wake_q
  sched/wake_q: Document wake_q_add()
  sched/wait: Fix rcuwait_wake_up() ordering

1 files changed, 5 insertions, 1 deletions

diff --git a/include/linux/sched/wake_q.h b/include/linux/sched/wake_q.h
index 10b19a192b2d..545f37138057 100644
--- a/include/linux/sched/wake_q.h
+++ b/include/linux/sched/wake_q.h
@@ -24,9 +24,13 @@
  * called near the end of a function. Otherwise, the list can be
  * re-initialized for later re-use by wake_q_init().
  *
- * Note that this can cause spurious wakeups. schedule() callers
+ * NOTE that this can cause spurious wakeups. schedule() callers
  * must ensure the call is done inside a loop, confirming that the
  * wakeup condition has in fact occurred.
+ *
+ * NOTE that there is no guarantee the wakeup will happen any later than the
+ * wake_q_add() location. Therefore task must be ready to be woken at the
+ * location of the wake_q_add().
  */
 
 #include <linux/sched.h>