Hello, Petr. On Wed, Oct 07, 2015 at 11:21:30AM +0200, Petr Mladek wrote: > Now, let's have one work: W, two workers: A, B, and try to queue > the same work to the two workers at the same time: It's a debug WARN condition to catch silly mistakes. It can have minor race conditions. ... > Second, we still need the busy waiting for the pending timer callback. Isn't that del_timer_sync()? > Yes, we could set some flag so that the call back does not queue > the work. But cancel_kthread_work_sync() still has to wait. > It could not return if there is still some pending operation > with the struct kthread_work. Otherwise, it never could > be freed a safe way. > > Also note that we still need the WORK_PENDING flag. Otherwise, we > would not be able to detect the race when timer is removed but > the callback has not run yet. Yeah, just use a state field as I wrote before. > Let me to repeat that using per-work and per-worker lock is not an > option either. We would need some crazy hacks to avoid ABBA deadlocks. > > > All in all, I would prefer to keep the original approach that is > heavily inspired by the workqueues. I think that it is actually > an advantage to reuse some working concept that reinventing wheels. At each turn, you come up with non-issues and declare that it needs to be full workqueue-like implementation but the issues you're raising seem all rather irrelevant. Can you please try to take a step back and put some distance from the implementation details of workqueue? Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>