Messages in this thread |  | | | Subject | Re: [PATCH 1/4] cpu_stop: implement stop_cpu[s]() | | From | Peter Zijlstra <> | | Date | Tue, 04 May 2010 10:43:40 +0200 |
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On Tue, 2010-05-04 at 09:03 +0200, Tejun Heo wrote: > On 05/04/2010 08:36 AM, Tejun Heo wrote: > > On 05/03/2010 03:26 PM, Peter Zijlstra wrote: > >> On Thu, 2010-04-22 at 18:09 +0200, Tejun Heo wrote: > >>> +static int cpu_stopper_thread(void *data) > >>> +{ > >>> + struct cpu_stopper *stopper = data; > >> > >> BUG_ON(stopper != __get_cpu_var(cpu_stopper)); ? > > > > Added. > > Now that I think more about it, there's a subtle race condition with > the above BUG_ON(). Stoppers are prepared by CPU_UP_PREPARE and > started by CPU_ONLINE but brought down by CPU_DEAD. IOW, they're > allowed to run detached from their designated CPUs between CPU_DYING > and CPU_DEAD (the reponsibility of guaranteeing target cpus's onliness > is on the callers). So, the above BUG_ON() might trigger spuriously > if a cpu goes down after brought online before its cpu_stopper had a > chance to pass through the BUG_ON() test.
Ah indeed. A well, drop it then, its not worth making a more complicated test.
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