On Tue 2015-07-28 13:18:22, Tejun Heo wrote: > Hello, > > On Tue, Jul 28, 2015 at 04:39:20PM +0200, Petr Mladek wrote: > > +/* > > + * Test whether @work is being queued from another work > > + * executing on the same kthread. > > + */ > > +static bool is_chained_work(struct kthread_worker *worker) > > +{ > > + struct kthread_worker *current_worker; > > + > > + current_worker = current_kthread_worker(); > > + /* > > + * Return %true if I'm a kthread worker executing a work item on > > + * the given @worker. > > + */ > > + return current_worker && current_worker == worker; > > +} > > I'm not sure full-on chained work detection is necessary here. > kthread worker's usages tend to be significantly simpler and draining > is only gonna be used for destruction. I think that it might be useful to detect bugs when someone depends on the worker when it is being destroyed. For example, I tried to convert "khubd" kthread and there was not easy to double check that this worked as expected. I actually think about replacing WARN_ON_ONCE(!is_chained_work(worker))) with WARN_ON(!is_chained_work(worker))) in queue_kthread_work, so that we get the warning for all misused workers. > > +void drain_kthread_worker(struct kthread_worker *worker) > > +{ > > + int flush_cnt = 0; > > + > > + spin_lock_irq(&worker->lock); > > + worker->nr_drainers++; > > + > > + while (!list_empty(&worker->work_list)) { > > + /* > > + * Unlock, so we could move forward. Note that queuing > > + * is limited by @nr_drainers > 0. > > + */ > > + spin_unlock_irq(&worker->lock); > > + > > + flush_kthread_worker(worker); > > + > > + if (++flush_cnt == 10 || > > + (flush_cnt % 100 == 0 && flush_cnt <= 1000)) > > + pr_warn("kthread worker %s: drain_kthread_worker() isn't complete after %u tries\n", > > + worker->task->comm, flush_cnt); > > + > > + spin_lock_irq(&worker->lock); > > + } > > I'd just do something like WARN_ONCE(flush_cnt++ > 10, "kthread worker: ..."). This would print the warning only for one broken worker. But I do not have strong opinion about it. Best Regards, Petr -- 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>