linux-kernel - Re: cgroup: rmdir() does not complete

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Date:	Thu, 9 Sep 2010 12:36:51 +0100 (BST)
From:	Mark Hills <mark@...o.org.uk>
To:	Balbir Singh <balbir@...ux.vnet.ibm.com>
cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	linux-kernel@...r.kernel.org
Subject: Re: cgroup: rmdir() does not complete

On Thu, 9 Sep 2010, Balbir Singh wrote:

> * Mark Hills <mark@...o.org.uk> [2010-09-09 11:01:45]:
> 
> > On Thu, 2 Sep 2010, KAMEZAWA Hiroyuki wrote:
> > 
> > [...]
> > > But hmm...it's curious who holds mutex and what happens.
> > 
> > I have a system showing the failure case (but still do not have a way to 
> > reliably repeat it)
> > 
> > Here are the two processes:
> > 
> > 23586 pts/0    RL+  5059:18 /net/homes/mhills/tmp/soaked-cgroup
> > 23685 pts/6    DL+    0:00 /net/homes/mhills/tmp/soaked-cgroup
> > 
> > 23586 spends almost all of its time in 'RL+' status, occasionally it is 
> > seen in 'DL+' status.
> > 
> > From my analysis before, both are blocked on rmdir(), but one is spinning, 
> > holding the lock on the /cgroup, and the other is waiting for the lock. If 
> > I strace 23586 then the rmdir() fails with EINTR.
> >
> 
> Any chance you can compile with debug cgroup subsystem and get
> information from there? 

I can, I'd like to experiment with a custom kernel next.

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.

Thanks

-- 
Mark
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