diff options
Diffstat (limited to 'kernel/futex.c')
| -rw-r--r-- | kernel/futex.c | 27 |
1 files changed, 23 insertions, 4 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index a5d2e74c89e0..c20f06f38ef3 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1295,10 +1295,20 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this, if (unlikely(should_fail_futex(true))) ret = -EFAULT; - if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) + if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) { ret = -EFAULT; - else if (curval != uval) - ret = -EINVAL; + } else if (curval != uval) { + /* + * If a unconditional UNLOCK_PI operation (user space did not + * try the TID->0 transition) raced with a waiter setting the + * FUTEX_WAITERS flag between get_user() and locking the hash + * bucket lock, retry the operation. + */ + if ((FUTEX_TID_MASK & curval) == uval) + ret = -EAGAIN; + else + ret = -EINVAL; + } if (ret) { raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock); return ret; @@ -1525,8 +1535,8 @@ void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, if (likely(&hb1->chain != &hb2->chain)) { plist_del(&q->list, &hb1->chain); hb_waiters_dec(hb1); - plist_add(&q->list, &hb2->chain); hb_waiters_inc(hb2); + plist_add(&q->list, &hb2->chain); q->lock_ptr = &hb2->lock; } get_futex_key_refs(key2); @@ -2623,6 +2633,15 @@ retry: if (ret == -EFAULT) goto pi_faulted; /* + * A unconditional UNLOCK_PI op raced against a waiter + * setting the FUTEX_WAITERS bit. Try again. + */ + if (ret == -EAGAIN) { + spin_unlock(&hb->lock); + put_futex_key(&key); + goto retry; + } + /* * wake_futex_pi has detected invalid state. Tell user * space. */ |