linux-kernel - Re: pidns memory leak

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Message-ID: <4ACD9ECC.90508@fr.ibm.com>
Date:	Thu, 08 Oct 2009 10:11:56 +0200
From:	Daniel Lezcano <dlezcano@...ibm.com>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
CC:	Pavel Emelianov <xemul@...nvz.org>,
	Sukadev Bhattiprolu <sukadev@...ibm.com>,
	Linux Containers <containers@...ts.osdl.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: pidns memory leak

Sukadev Bhattiprolu wrote:
> Still digging through some traces, but below I have some questions that 
> I am still trying to answer.
> 
>> I am not sure what you mean by 'struct pids' but what I observed is:
> 
> Ok, I see that too. If pids leak, then pid-namespace will leak too.
> Do you see any leaks in proc_inode_cache ?

Yes, right. It leaks too.

>> pid_2 and pid_namespace (as they are named in /proc/slabinfo) are never  
>> decremented.
>>
>>> And the pid_namespace does not seem to reproduce for me, with out the
>>> 'ls -al /proc/...' above, or with the simpler 'ns_exec' approach to
>>> creating pid namespace.
>> I tried to write a simpler program but I failed to reproduce it.
>>
>>> I am going through the code for lxc-execute, but does it remount /proc  
>>> in the container ?
>> Right, the parent does a clone(NEWMNT|NEWPID|NEWIPC|NEWUTS), wait for  
>> the child while this one (pid 1) 'execs' the lxc-init process. This  
>> program mounts /proc and fork-exec the command passed as parameter (here  
>> 'sleep 3600').
>>
>> Without this intermediate process, the leak *seems* not happening.
>>
>> If you don't access /proc/<pid>/<file>, the leak is not happening.
> 
> I could not see the code for that.  Does lxc-stop unmount /proc too ?
> Or is the umount expected to happen automatically after all processes
> in the container are killed ?

The umount is expected to happen automatically. I can not access the 
container from the outside to umount /proc.
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