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Date: Fri, 21 Dec 2018 14:02:10 -0500
From: Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: OOM notification for cgroupsv1 broken in 4.19
Message-ID: <20181221190210.GB5395@cmpxchg.org>
References: <5ba5ba06-554c-d1ec-0967-b1d3486d0699@fnal.gov>
 <20181221153302.GB6410@dhcp22.suse.cz>
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To: Michal Hocko <mhocko@kernel.org>
Cc: Burt Holzman <burt@fnal.gov>, "vdavydov.dev@gmail.com" <vdavydov.dev@gmail.com>, "cgroups@vger.kernel.org" <cgroups@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>

On Fri, Dec 21, 2018 at 04:33:02PM +0100, Michal Hocko wrote:
> From 51633f683173013741f4d0ab3e31bae575341c55 Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@suse.com>
> Date: Fri, 21 Dec 2018 16:28:29 +0100
> Subject: [PATCH] memcg, oom: notify on oom killer invocation from the charge
>  path
> 
> Burt Holzman has noticed that memcg v1 doesn't notify about OOM events
> via eventfd anymore. The reason is that 29ef680ae7c2 ("memcg, oom: move
> out_of_memory back to the charge path") has moved the oom handling back
> to the charge path. While doing so the notification was left behind in
> mem_cgroup_oom_synchronize.
> 
> Fix the issue by replicating the oom hierarchy locking and the
> notification.
> 
> Reported-by: Burt Holzman <burt@fnal.gov>
> Fixes: 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the charge path")
> Cc: stable # 4.19+
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Looks good to me. The async side really does too much other stuff to
cleanly share code between them, so I don't mind separate code even if
it means they both have to do the mark, lock, notify dance.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>