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Subject: Re: cgroup: rmdir() does not complete
From: Peter Zijlstra <peterz@infradead.org>
To: Mark Hills <mark@pogo.org.uk>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
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Date: Thu, 09 Sep 2010 13:50:17 +0200
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On Thu, 2010-09-09 at 12:36 +0100, Mark Hills wrote:

> I am still finding the problem incredibly hard to reproduce, so I'd like 
> to observe as much data as possible from the current case before 
> rebooting. If I could capture some kind of stack trace in the kernel for 
> the running process that would be great, any suggestions appreciated.

echo l > /proc/sysrq-trigger

another thing you can do is run something like: perf record -gp $pid
which will give you a profile of that task.