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Date: Wed, 30 Aug 2017 17:43:15 +0200
From: Michal Hocko <mhocko@kernel.org>
Subject: Re: possible circular locking dependency
 mmap_sem/cpu_hotplug_lock.rw_sem
Message-ID: <20170830154315.sa57wasw64rvnuhe@dhcp22.suse.cz>
References: <20170807140947.nhfz2gel6wytl6ia@shodan.usersys.redhat.com>
 <alpine.DEB.2.20.1708161605050.1987@nanos>
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To: Thomas Gleixner <tglx@linutronix.de>
Cc: Artem Savkov <asavkov@redhat.com>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, LKML <linux-kernel@vger.kernel.org>, Johannes Weiner <hannes@cmpxchg.org>, linux-mm@kvack.org

The previous patch is insufficient. drain_all_stock can still race with
the memory offline callback and the underlying memcg disappear. So we
need to be more careful and pin the css on the memcg. This patch
instead...
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