futex: Unlock hb->lock in futex_wait_requeue_pi() error path

futex: Unlock hb->lock in futex_wait_requeue_pi() error path

futex_wait_requeue_pi() calls futex_wait_setup(). If
futex_wait_setup() succeeds it returns with hb->lock held and
preemption disabled. Now the sanity check after this does:

        if (match_futex(&q.key, &key2)) {
	   	ret = -EINVAL;
		goto out_put_keys;
	}

which releases the keys but does not release hb->lock.

So we happily return to user space with hb->lock held and therefor
preemption disabled.

Unlock hb->lock before taking the exit route.

Reported-by: Dave "Trinity" Jones <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Darren Hart <[email protected]>
Reviewed-by: Davidlohr Bueso <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409112318500.4178@nanos
Signed-off-by: Thomas Gleixner <[email protected]>