Messages in this thread | | | Date | Fri, 24 Oct 2008 12:29:57 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/7] work_on_cpu: helper for doing task on a CPU. |
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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.
Once again, the "cpu_hotplug_begin()" lock is not special. You can't use work_on_cpu() under (say) rtnl_lock() for the same reason, this lock is used by work->func() too.
Perhaps I missed something, and work_on_cpu() is really important for cpu-hotplug path?
Oleg.
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