Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH 1/7] work_on_cpu: helper for doing task on a CPU. | Date | Fri, 24 Oct 2008 22:18:50 +1100 |
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On Friday 24 October 2008 21:29:57 Oleg Nesterov wrote: > On 10/24, Gautham R Shenoy wrote: > > On Fri, Oct 24, 2008 at 02:04:35PM +1100, Rusty Russell wrote: > > > I think we should BUG_ON(per_cpu(cpu_state, cpuid) != CPU_DEAD) to > > > ensure we never use work_on_cpu in the hotplug cpu path. Then we use > > > smp_call_function() for that hard intel_cacheinfo case. Finally, we > > > fix the cpu hotplug path to use schedule_work_on() itself rather than > > > playing games with cpumask. > > > > > > If you agree, I'll spin the patches... > > > > How about the following? > > > > We go with this method, but instead of piggybacking on > > the generic kevents workqueue, we create our own on_each_cpu_wq, for this > > purpose. > > Gautham, Rusty, I am a bit lost on this discussion... > > Why should we care about this deadlock? Just do not use work_on_cpu() from > the hotplug cpu path, that is all.
No, I agree with you (Oleg). Gautham's proposal would work, but at the cost of yet another thread per CPU :(
Since we know how to handle the one problematic case Oleg spotted, *and* we know how to BUG_ON to make sure noone introduces new ones, I think this is clearest.
Thanks, Rusty.
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