On Fri, Apr 18, 2014 at 12:08 AM, Tejun Heo <t...@kernel.org> wrote: > 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.
You are right. We need a additional atomic check. Thanks, Lai > > Thanks. > > -- > tejun > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
