diff options
| -rw-r--r-- | kernel/futex/requeue.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/kernel/futex/requeue.c b/kernel/futex/requeue.c index 79823ad13..b3f4a4bcc 100644 --- a/kernel/futex/requeue.c +++ b/kernel/futex/requeue.c @@ -154,8 +154,16 @@ static inline void futex_requeue_pi_complete(struct futex_q *q, int locked) } while (!atomic_try_cmpxchg(&q->requeue_state, &old, new)); #ifdef CONFIG_PREEMPT_RT - /* If the waiter interleaved with the requeue let it know */ - if (unlikely(old == Q_REQUEUE_PI_WAIT)) + /* + * The waiter in futex_requeue_pi_wakeup_sync() can interleave with the + * wake below: It will assign Q_REQUEUE_PI_IN_PROGRESS and here it will + * be updated to Q_REQUEUE_PI_LOCKED (locked = 1). The rcuwait_wait_event() + * will already read Q_REQUEUE_PI_LOCKED and skip the schedule() invocation, + * leading to an access of futex_q::requeue_wait after the waiter returned. + * In this case only we skip the wake here and rely on following wake in + * requeue_pi_wake_futex() to perform the wake if needed. + */ + if (unlikely(old == Q_REQUEUE_PI_WAIT) && new != Q_REQUEUE_PI_LOCKED) rcuwait_wake_up(&q->requeue_wait); #endif } |