On Wed, Feb 24, 2016 at 05:18:05PM +0100, Petr Mladek wrote:
> @@ -770,7 +782,22 @@ void delayed_kthread_work_timer_fn(unsigned long __data)
> if (WARN_ON_ONCE(!worker))
> return;
>
> - spin_lock(&worker->lock);
> + /*
> + * We might be unable to take the lock if someone is trying to
> + * cancel this work and calls del_timer_sync() when this callback
> + * has already been removed from the timer list.
> + */
> + while (!spin_trylock(&worker->lock)) {
> + /*
> + * Busy wait with spin_is_locked() to avoid cache bouncing.
> + * Break when canceling is set to avoid a deadlock.
> + */
> + do {
> + if (work->canceling)
> + return;
> + cpu_relax();
> + } while (spin_is_locked(&worker->lock));
> + }
> /* Work must not be used with more workers, see queue_kthread_work(). */
> WARN_ON_ONCE(work->worker != worker);
>
This is pretty vile; why can't you drop the lock over del_timer_sync() ?
