Messages in this thread | | | Date | Sun, 7 Jan 2007 16:13:28 +0530 | From | Srivatsa Vaddagiri <> | Subject | Re: [PATCH] fix-flush_workqueue-vs-cpu_dead-race-update |
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On Sat, Jan 06, 2007 at 08:34:16PM +0300, Oleg Nesterov wrote: > I suspect this can't help either. > > The problem is that flush_workqueue() may be called while cpu hotplug event > in progress and CPU_DEAD waits for kthread_stop(), so we have the same dead > lock if work->func() does flush_workqueue(). This means that Andrew's change > to use preempt_disable() is good and anyway needed.
Well ..a lock_cpu_hotplug() in run_workqueue() and support for recursive calls to lock_cpu_hotplug() by the same thread will avoid the problem you mention. This will need changes to task_struct to track the recursion depth. Alternately this can be supported w/o changes to task_struct by 'biasing' readers over writers as I believe Gautham's patches [1] do.
1. http://lkml.org/lkml/2006/10/26/65
-- Regards, vatsa
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