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Diffstat (limited to 'kernel/futex.c')
-rw-r--r--kernel/futex.c27
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.
*/