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Date: Wed, 31 Oct 2012 11:42:28 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
Subject: Re: zram OOM behavior
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To: Luigi Semenzato <semenzato@google.com>
Cc: Minchan Kim <minchan@kernel.org>, linux-mm@kvack.org, Dan Magenheimer <dan.magenheimer@oracle.com>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Sonny Rao <sonnyrao@google.com>

On Tue, 30 Oct 2012, Luigi Semenzato wrote:

> For completeness, I would like to report that the page fault in
> mm_release looks legitimate.  The fault happens near here:
> 
> if (unlikely(tsk->robust_list)) {
>     exit_robust_list(tsk);
>     tsk->robust_list = NULL;
> }
> 
> and robust_list is a userspace structure.
> 

This is the only place where the hang occurs when there are several 
threads in the exit path with PF_EXITING and it causes the oom killer to 
defer killing a process?  If that's the case, then a simple 
tsk->robust_list check would be sufficient to avoid deferring incorrectly.

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