Hello, Nikolay. On Thu, Dec 17, 2015 at 12:46:10PM +0200, Nikolay Borisov wrote: > diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c > index 493c38e08bd2..ccbbf7823cf3 100644 > --- a/drivers/md/dm-thin.c > +++ b/drivers/md/dm-thin.c > @@ -3506,8 +3506,8 @@ static void pool_postsuspend(struct dm_target *ti) > struct pool_c *pt = ti->private; > struct pool *pool = pt->pool; > > - cancel_delayed_work(&pool->waker); > - cancel_delayed_work(&pool->no_space_timeout); > + cancel_delayed_work_sync(&pool->waker); > + cancel_delayed_work_sync(&pool->no_space_timeout); > flush_workqueue(pool->wq); > (void) commit(pool); > } > > And this seems to have resolved the crashes. For the past 24 hours I > haven't seen a single server crash whereas before at least 3-5 servers > would crash. So, that's an obvious bug on dm-thin side. > Given that, it seems like a race condition between destroying the > workqueue from dm-thin and cancelling all the delayed work. > > Tejun, I've looked at cancel_delayed_work/cancel_delayed_work_sync and > they both call try_to_grab_pending and then their function diverges. Is > it possible that there is a latent race condition between canceling the > delayed work and the subsequent re-scheduling of the work item? It's just the wrong variant being used. cancel_delayed_work() doesn't guarantee that the work item isn't running on return. If the work item was running and the workqueue is destroyed afterwards, it may end up trying to requeue itself on a destroyed workqueue. Thanks. -- tejun -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
