Re: [PATCH v5 08/20] kthread: Allow to cancel kthread work
From: Peter Zijlstra <peterz@infradead.org>
Date: 2016-02-25 12:59:47
Also in:
linux-mm, lkml
On Wed, Feb 24, 2016 at 05:18:05PM +0100, Petr Mladek wrote:
quoted hunk ↗ jump to hunk
@@ -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() ? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>