linux-kernel - Re: [patch -mm 4/9 v2] oom: remove compulsory panic_on

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Date:	Mon, 22 Feb 2010 12:59:15 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Lubos Lunak <l.lunak@...e.cz>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch -mm 4/9 v2] oom: remove compulsory panic_on_oom mode

On Mon, 22 Feb 2010, Daisuke Nishimura wrote:

> hmm, I can agree with you. But I think we need some trick to distinguish normal VM_FAULT_OOM
> and memcg's VM_FAULT_OOM(the current itself was killed by memcg's oom, so exited the retry)
> at mem_cgroup_oom_called() to avoid the system from panic when panic_on_oom is enabled.
> (Mark the task which is being killed by memcg's oom ?).
> 

pagefault_out_of_memory() should use mem_cgroup_from_task(current) and 
then call mem_cgroup_out_of_memory() when it's non-NULL.  
select_bad_process() will return ERR_PTR(-1UL) if there is an already oom 
killed task attached to the memcg, so we can use that to avoid the 
panic_on_oom.  The setting of that sysctl doesn't imply that we can't scan 
the tasklist, it simply means we can't kill anything as a result of an 
oom.
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