linux-kernel - 2.6.32 cgroup regression

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Message-ID: <4C74274D.9060300@akamai.com>
Date:	Tue, 24 Aug 2010 13:10:53 -0700
From:	Josh Hunt <johunt@...mai.com>
To:	efault@....de, a.p.zijlstra@...llo.nl, mingo@...e.hu
CC:	linux-kernel@...r.kernel.org
Subject: 2.6.32 cgroup regression

This commit makes the ltp cpuctl latency test #2 hang indefinitely:

commit b5d9d734a53e0204aab0089079cbde2a1285a38f
Author: Mike Galbraith <efault@....de>
Date:   Tue Sep 8 11:12:28 2009 +0200

    sched: Ensure that a child can't gain time over it's parent after fork()

When I revert this commit the test progresses as it did in 2.6.31. I
have seen this issue on 2.6.32 and 2.6.32.19. The hang goes away in
2.6.33 starting with this commit:

commit 88ec22d3edb72b261f8628226cd543589a6d5e1b
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date:   Wed Dec 16 18:04:41 2009 +0100

    sched: Remove the cfs_rq dependency from set_task_cpu()

Even though this appears to be resolved in 2.6.33, I am reporting it
because 2.6.32 is the "long-term stable release".

My test system is a single socket dual core amd -
model name	: Dual Core AMD Opteron(tm) Processor 180
with 4GB of RAM.
Kernel config file attached.

The issue is easily reproducible for me by downloading and building ltp,
then running
testcases/kernel/controllers/cpuctl/run_cpuctl_latency_test.sh 2

Please let me know if you need any other information to help reproduce
this issue.

Thanks
Josh

View attachment "config" of type "text/plain" (61497 bytes)