Messages in this thread | | | Date | Thu, 23 Jan 2014 18:02:42 +0100 | From | Oleg Nesterov <> | Subject | Re: Deadlock between cpu_hotplug_begin and cpu_add_remove_lock |
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On 01/23, Srivatsa S. Bhat wrote: > > On 01/23/2014 12:48 AM, Oleg Nesterov wrote: > > On 01/22, Srivatsa S. Bhat wrote: > >> > >> Wait a min, that _will_ actually work for all cases because I have provided > >> an option to invoke _any_ arbitrary function as the "setup" routine. > > > > And probably the generic solution makes sense. I am not sure I actually > > understand the semantics of register_allcpu_notifier(), but the problem > > it tries to solve looks clear/valid. > > > > Thank you. But I was wondering whether its usage is a bit unintuitive/ > convoluted. So I was contemplating between going with that solution or the > below one, where the call-sites are expected to do: > > cpu_maps_update_begin(); > for_each_online_cpu(cpu) { > ... > } > __register_cpu_notifier(); //use the __reg() variant, which doesn't take locks > cpu_maps_update_done(); > > Of course, that requires exporting the functions cpu_maps_update_begin/done(), > but this latter form of callback registration might look more natural.
Yes, I thought about this too ;)
> But for some of the other call-sites, we might have to use one > of the solutions mentioned above.
Yes, yes, sure, I agree.
I suggested this change only for discussion, for the case we need an "urgent" fix without changes outside of drivers/md/. The generic solution is better.
Oleg.
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