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

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Date:	Tue, 9 Jul 2013 15:54:50 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	azurIt <azurit@...ox.sk>
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>
Subject: Re: [PATCH for 3.2] memcg: do not trap chargers with full callstack
 on OOM

On Tue 09-07-13 15:19:21, 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)?

Btw. the bellow patch might help us to point to the exit path which
leaves wait_on_memcg without mem_cgroup_oom_synchronize:
---
diff --git a/kernel/exit.c b/kernel/exit.c
index e6e01b9..ad472e0 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -895,6 +895,7 @@ NORET_TYPE void do_exit(long code)
 
 	profile_task_exit(tsk);
 
+	WARN_ON(current->memcg_oom.wait_on_memcg);
 	WARN_ON(blk_needs_flush_plug(tsk));
 
 	if (unlikely(in_interrupt()))
-- 
Michal Hocko
SUSE Labs
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