Messages in this thread | | | Subject | Re: 2.6.32 cgroup regression | From | Mike Galbraith <> | Date | Wed, 25 Aug 2010 07:56:01 +0200 |
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On Tue, 2010-08-24 at 13:10 -0700, Josh Hunt wrote: > This commit makes the ltp cpuctl latency test #2 hang indefinitely: > > commit b5d9d734a53e0204aab0089079cbde2a1285a38f > Author: Mike Galbraith <efault@gmx.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()
Ouch. Yeah, that commit is buggy, and never got fixed up in stable. Reverting it will restore a slightly less buggy, but not very good situation. Getting the fork problems all fixed up took a while. (quick fix vs revert didn't help your testcase)
> 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@chello.nl> > Date: Wed Dec 16 18:04:41 2009 +0100 > > sched: Remove the cfs_rq dependency from set_task_cpu()
Excellent timing you have. I have a tree of backports, but I wasn't counting this commit as a must have, merely highly desirable. This testcase showed that it's a needed fix.
> 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".
Yeah, there are a _lot_ of fixes that should wander back to 32-stable.
> 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.
No, the testcase works well. Thanks.
-Mike
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