On Fri, Nov 03, 2017 at 05:30:28PM -0500, Julia Cartwright wrote: > This check was an attempt to protect against a race with put_pi_state() > by ensuring that the pi_state_list was consistent across the > unlock/lock of pi_lock. > > However, as of commit 153fbd1226fb3 ("futex: Fix more put_pi_state() vs. > exit_pi_state_list() races"), this check is no longer necessary because > we now hold a reference to the pi_state object across the unlock/lock of > pi_lock. This reference guarantees that a put_pi_state() on another CPU > won't rip the pi_state object from the list when we drop pi_lock.
> @@ -929,17 +928,6 @@ void exit_pi_state_list(struct task_struct *curr) > spin_lock(&hb->lock); > raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock); > raw_spin_lock(&curr->pi_lock); > - /* > - * We dropped the pi-lock, so re-check whether this > - * task still owns the PI-state: > - */ > - if (head->next != next) { Quite possibly you're right, but I would sleep a whole lot better if that were to remain a WARN. You never know with this futex stuff :-)