linux-kernel - Re: pidns memory leak

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Date:	Wed, 7 Oct 2009 20:08:28 -0700
From:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:	Daniel Lezcano <dlezcano@...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

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 ?

>
> 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 ?

Sukadev
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