Upgrade to 4.4.50-rt62

[kvmfornfv.git] / kernel / kernel / futex.c

diff --git a/kernel/kernel/futex.c b/kernel/kernel/futex.c
index 02bb869..0596234 100644 (file)
--- a/kernel/kernel/futex.c
+++ b/kernel/kernel/futex.c
@@ -1247,10 +1247,20 @@ 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;
@@ -1278,7 +1288,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this,
         * deboost first (and lose our higher priority), then the task might get
         * scheduled away before the wake up can take place.
         */
-       spin_unlock(&hb->lock);
+       deboost |= spin_unlock_no_deboost(&hb->lock);
        wake_up_q(&wake_q);
        wake_up_q_sleeper(&wake_sleeper_q);
        if (deboost)
@@ -1479,8 +1489,8 @@ 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);
@@ -2552,6 +2562,15 @@ 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.