Re: [PATCH 2/2] RT: remove "paranoid" limit in push_rt_task

From: Gregory Haskins
Date: Fri Oct 03 2008 - 13:23:29 EST


Chirag Jog wrote:
> * Gilles Carry <Gilles.Carry@xxxxxxxx> [2008-10-03 15:46:59]:
>
>
>> Sorry Greg,
>>
>> Neither PPC64 nor Intel64 make it with this patch.
>> At boot time, it stops at the BUG_ON you added:
>> 0xc00000000004eca4 is in push_rt_task (kernel/sched_rt.c:1102)
>>
> I am also confirming this issue gilles reported.
>
> Although, i have a question:
> When we enable group scheduling (CONFIG_RT_GROUP_SCHED),
> all the problems disappear.
> After skimming through the rt scheduler code, I don't feel group
> scheduling alters the behavior of push/pull strategies in any way.
>
> So I am wonder whether enabling group scheduling
> actually solves the problem or just makes it tough
> to recreate?
>
Hi Chirag,


The issue that Gilles pointed me at is a race condition. I do not
suspect GROUP_SCHED itself has anything to do with the problem other
than it changes the timing. HTH!

-Greg



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