Re: [stable] Regression in segfault on halt

From: Holger HoffstÃtte
Date: Sun Dec 20 2009 - 10:24:52 EST

(sorry for the dupes)

Mike Galbraith wrote:
> On Sun, 2009-12-20 at 14:27 +0100, Holger HoffstÃtte wrote:
>> Took me some time (still learning git - I usually use hg) but I just
>> managed to fix it by reverting not the bisected revision (won't compile
>> any longer), but the follow-up "cleanup & fix":
>> >From 35c1ee3e78766d5666f418af638def9c67e63ecb Mon Sep 17 00:00:00 2001
>> From: Mike Galbraith <efault@xxxxxx>
>> Date: Tue, 10 Nov 2009 03:50:02 +0100
>> Subject: [PATCH] sched: Fix and clean up rate-limit newidle code
>> commit eae0c9dfb534cb3449888b9601228efa6480fdb5 upstream.
>> Commit 1b9508f, "Rate-limit newidle" has been confirmed to fix
>> the netperf UDP loopback regression reported by Alex Shi.
>> This is a cleanup and a fix:
>> - moved to a more out of the way spot
>> - fix to ensure that balancing doesn't try to balance
>> runqueues which haven't gone online yet, which can
>> mess up CPU enumeration during boot.
>> Reported-by: Alex Shi <alex.shi@xxxxxxxxx>
>> Reported-by: Zhang, Yanmin <yanmin_zhang@xxxxxxxxxxxxxxx>
>> Signed-off-by: Mike Galbraith <efault@xxxxxx>
>> Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
>> LKML-Reference: <1257821402.5648.17.camel@xxxxxxxxxxxxxxxx>
>> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
>> aka:
>> Reverting this from a clean 32.2 tree results in a kernel with newidle
>> fix, but still working halt/reboot. The only difference between this and
>> the bisected one is the additional change in cpumask handling.
>> That was more fun than expected :)
> Egad. Reverting the cpumask bit alone cures the problem?

Yup. I manually changed both cpumask_copy(..) lines back to
cpumask_setall(..) in a clean .32.2 tree and can halt the resulting kernel
without problems.

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