linux-kernel - Re: [PATCH for 3.2] memcg: do not trap chargers with full callstack on OOM

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Message-Id: <20130714012641.C2DA4E05@pobox.sk>
Date:	Sun, 14 Jul 2013 01:26:41 +0200
From:	"azurIt" <azurit@...ox.sk>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	cgroups mailinglist <cgroups@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	<righi.andrea@...il.com>
Subject: Re: [PATCH for 3.2] memcg: do not trap chargers with full callstack on OOM

> CC: "Johannes Weiner" <hannes@...xchg.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, "cgroups mailinglist" <cgroups@...r.kernel.org>, "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>, righi.andrea@...il.com
>On Wed 10-07-13 18:25:06, azurIt wrote:
>> >> Now i realized that i forgot to remove UID from that cgroup before
>> >> trying to remove it, so cgroup cannot be removed anyway (we are using
>> >> third party cgroup called cgroup-uid from Andrea Righi, which is able
>> >> to associate all user's processes with target cgroup). Look here for
>> >> cgroup-uid patch:
>> >> https://www.develer.com/~arighi/linux/patches/cgroup-uid/cgroup-uid-v8.patch
>> >> 
>> >> ANYWAY, i'm 101% sure that 'tasks' file was empty and 'under_oom' was
>> >> permanently '1'.
>> >
>> >This is really strange. Could you post the whole diff against stable
>> >tree you are using (except for grsecurity stuff and the above cgroup-uid
>> >patch)?
>> 
>> 
>> Here are all patches which i applied to kernel 3.2.48 in my last test:
>> http://watchdog.sk/lkml/patches3/
>
>The two patches from Johannes seem correct.
>
>>From a quick look even grsecurity patchset shouldn't interfere as it
>doesn't seem to put any code between handle_mm_fault and mm_fault_error
>and there also doesn't seem to be any new handle_mm_fault call sites.
>
>But I cannot tell there aren't other code paths which would lead to a
>memcg charge, thus oom, without proper FAULT_FLAG_KERNEL handling.


Michal,

now i can definitely confirm that problem with unremovable cgroups persists. What info do you need from me? I applied also your little 'WARN_ON' patch.

azur
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