linux-kernel - Re: [PATCH for-4.6-fixes] memcg: remove lru_add_drain_all() invocation from mem_cgroup_move

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Message-ID: <20160421150024.GB2749@pathway.suse.cz>
Date:	Thu, 21 Apr 2016 17:00:24 +0200
From:	Petr Mladek <pmladek@...e.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
	cgroups@...r.kernel.org, Cyril Hrubis <chrubis@...e.cz>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH for-4.6-fixes] memcg: remove lru_add_drain_all()
 invocation from mem_cgroup_move_charge()

On Wed 2016-04-20 23:27:05, Michal Hocko wrote:
> On Wed 20-04-16 17:29:22, Tejun Heo wrote:
> > Hello, Michal.
> > 
> > On Sun, Apr 17, 2016 at 08:07:48AM -0400, Michal Hocko wrote:
> [...]
> > > I liked your proposal when mem_cgroup_move_charge would be called from a
> > > context which doesn't hold the problematic rwsem much more. Would that
> > > be too intrusive for the stable backport?
> > 
> > Yeah, I'm working on the fix but let's plug this one first as it seems
> > really easy to trigger.  I got a couple off-list reports (in and
> > outside fb) of this triggering.
> 
> Sure, I think we can use this for an immediate workaround. Nevertheless
> we want to have a full fix and do not rely on this being the only
> problem. I would eventually like to reintroduce the draining later when
> we have a better fix because even though this is not a correctness
> problem I think we should try hard to not leave anything behind.
> 
> That being said:
> Acked-by: Michal Hocko <mhocko@...e.com>

Just for completeness. The problematic LTP test is running for hours
with this patch. Feel free to add:

Tested-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr