Messages in this thread | | | Subject | Re: crash in 3.12.51 (likely in 3.12.52 as well) in timer code | From | Mike Galbraith <> | Date | Thu, 04 Feb 2016 13:17:44 +0100 |
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On Thu, 2016-02-04 at 13:51 +0200, Nikolay Borisov wrote: > > On 02/04/2016 01:32 PM, Mike Galbraith wrote: > > On Wed, 2016-02-03 at 12:58 +0200, Nikolay Borisov wrote: > > > > > > So in this case the prev/next entries do not look like corrupted, > > > whereas > > > when manipulating the list inside detach_timer they do. This is > > > really > > > odd, any ideas how to further debug this? > > > > Suspiciously similar to https://lkml.org/lkml/2016/2/4/247 > > Right, I've been cursory following this thread but I was left with the > impression this only occurs on machines where the CPU can go offline, > currently the server on which this happened should never offline any of > its CPUs since the power management is disabled (though I will have to > double check this).
AFAIU, hotplug isn't required, only mod_delayed_work() being called from a different CPU than where the timer was born, migrating it at a bad time.
> On a different note - is there a way to safely reproduce this so I can > test the suggested fix by Thomas?
Hm, write a module to beat mod_delayed_work() to pulp with a NR_CPUS horde, and run it in a vm where you don't care about shrapnel?
-Mike
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