[PATCH] Add smp_mb__after_clear_bit() to unlock_kiocb()

Add smp_mb__after_clear_bit() to unlock_kiocb()

AIO's use of wait_on_bit_lock()/wake_up_bit() forgot to add a barrier
between clearing its lock bit and calling wake_up_bit() so wake_up_bit()'s
unlocked waitqueue_active() can race.  This puts AIO's use in line with the
others and the comment above wake_up_bit().

Signed-off-by: Zach Brown <zach.brown@oracle.com>
Acked-by: Benjamin LaHaise <bcrl@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/aio.c

@@ -562,6 +562,7 @@ static inline void lock_kiocb(struct kiocb *iocb)
 static inline void unlock_kiocb(struct kiocb *iocb)
 {
 	kiocbClearLocked(iocb);
+	smp_mb__after_clear_bit();
 	wake_up_bit(&iocb->ki_flags, KIF_LOCKED);
 }