linux-kernel - Re: possible circular locking dependency mmap_sem/cpu_hotplug_lock.rw

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Message-ID: <20170831121908.kin3mm25ebszhpvn@shodan.usersys.redhat.com>
Date:   Thu, 31 Aug 2017 14:19:37 +0200
From:   Artem Savkov <asavkov@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org
Subject: Re: possible circular locking dependency
 mmap_sem/cpu_hotplug_lock.rw_sem

On Thu, Aug 31, 2017 at 02:09:51PM +0200, Michal Hocko wrote:
> On Thu 31-08-17 13:10:06, Artem Savkov wrote:
> > Hi Michal,
> > 
> > On Wed, Aug 30, 2017 at 05:43:15PM +0200, Michal Hocko wrote:
> > > 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...
> > 
> > Tried this on top of rc7 and it does fix the splat for me.
> 
> Thanks for testing! Can I assume your Tested-by?

Didn't test much more than the case that was causing it, but yes.

Reported-and-tested-by: Artem Savkov <asavkov@...hat.com>

-- 
Regards,
  Artem