Hello, On Tue, Jun 24, 2014 at 08:05:07PM -0700, Austin Schuh wrote: > > I can see no reason why manual completion would behave differently > > from flush_work() in this case. > > I went looking for a short trace in my original log to show the problem, > and instead found evidence of the second problem. I still like the shorter > flush_work call, but that's not my call. So, are you saying that the original issue you reported isn't actually a problem? But didn't you imply that changing the waiting mechanism fixed a deadlock or was that a false positive? > I did find this comment in the process_one_work function. Sounds like this > could be better documented. Yeah, we prolly should beef up Documentation/workqueue.txt with information on general usage. > I spent some more time debugging, and I am seeing that tsk_is_pi_blocked is > returning 1 in sched_submit_work (kernel/sched/core.c). It looks > like sched_submit_work is not detecting that the worker task is blocked on > a mutex. The function unplugs the block layer and doesn't have much to do with workqueue although it has "_work" in its name. > This looks very RT related right now. I see 2 problems from my reading > (and experimentation). The first is that the second worker isn't getting > started because tsk_is_pi_blocked is reporting that the task isn't blocked > on a mutex. The second is that even if another worker needs to be > scheduled because the original worker is blocked on a mutex, we need the > pool lock to schedule another worker. The pool lock can be acquired by any > CPU, and is a spin_lock. If we end up on the slow path for the pool lock, > we hit BUG_ON(rt_mutex_real_waiter(task->pi_blocked_on)) > in task_blocks_on_rt_mutex in rtmutex.c. I'm not sure how to deal with > either problem. > > Hopefully I've got all my facts right... Debugging kernel code is a whole > new world from userspace code. I don't have much idea how RT kernel works either. Can you reproduce the issues that you see on mainline? Thanks. -- tejun _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
