Messages in this thread | | | Date | Tue, 21 May 2013 16:52:43 +0200 | From | Heiko Carstens <> | Subject | Re: Lost IPIs during CPU Hotplug |
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On Mon, May 20, 2013 at 02:37:43PM +0200, Heiko Carstens wrote: > I just got a dump from a system running a 3.0.something kernel, however I > think the problem exists with current kernels as well. > > Testcase was some I/O intense workload together with cpu hotplug stress. > > When trying to bring a cpu online we got an endless loop on the cpu that > issued the cpu_up and called smp_call_function_single() within its cpu > hotplug notifier:
[...]
> It looks to me like the IPI(s) was lost when cpu 3 was brought down before:
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> So it looks to me like yet another CPU_DYING cpu hotplug notifier is needed > for the generic smp code, which looks for pending IPIs on the to be brought > down cpu and executes them. > > Does that make sense?
Ok, I was able to reproduce it. And the fix should be in the s390 specific arch code within __cpu_disable() just before the cpu gets removed from the cpu online mask. No idea why this never has been seen before.
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