Messages in this thread | | | Date | Thu, 17 Apr 2014 12:08:28 -0400 | From | Tejun Heo <> | Subject | Re: [PATCH 1/2] workqueue: rescuer_thread() processes all pwqs before exit |
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Hello, Lai.
On Fri, Apr 18, 2014 at 12:04:29AM +0800, Lai Jiangshan wrote: > > I don't think this is reliable. What if mayday requests take place > > between wq_mayday_lock and kthread_should_stop() check? We'll > > probably need to run through mayday list after checking should_stop. > > It is destroy_workqueue()'s responsibility to avoid this. > destroy_workqueue() should drain all works and refuse any new work queued > on the wq before destroy the wq. > > So since there is no works, there is no new mayday request, > and there is no mayday request take place between wq_mayday_lock > and kthread_should_stop() check.
Hmmm? Isn't this the same race condition that you tried to remove by relocating the test? It doesn't matter what destroy_workqueue() does, the rescuer may get preempted inbetween and anything can happen inbetween including someone maydaying and initiation of destroy_workqueue(). Your patch doesn't change the situation at all. It can still return with non-empty mayday list.
Thanks.
-- tejun
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