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Date: Fri, 12 Aug 2016 11:43:19 +0200
From: Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH 09/10] vhost, mm: make sure that oom_reaper doesn't reap
 memory read by vhost
Message-ID: <20160812094319.GG3639@dhcp22.suse.cz>
References: <1469734954-31247-1-git-send-email-mhocko@kernel.org>
 <1469734954-31247-10-git-send-email-mhocko@kernel.org>
 <20160728233359-mutt-send-email-mst@kernel.org>
 <20160729060422.GA5504@dhcp22.suse.cz>
 <20160729161039-mutt-send-email-mst@kernel.org>
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, Oleg Nesterov <oleg@redhat.com>, David Rientjes <rientjes@google.com>, Vladimir Davydov <vdavydov@parallels.com>

On Fri 29-07-16 16:14:10, Michael S. Tsirkin wrote:
> On Fri, Jul 29, 2016 at 08:04:22AM +0200, Michal Hocko wrote:
> > On Thu 28-07-16 23:41:53, Michael S. Tsirkin wrote:
[...]
> > > 
> > > > +	 */
> > > > +	set_bit(MMF_UNSTABLE, &mm->flags);
> > > > +
> > > 
> > > I would really prefer a callback that vhost would register
> > > and stop all accesses. Tell me if you need help on above idea.
> > 
> > 
> > Well, in order to make callback workable the oom reaper would have to
> > synchronize with the said callback until it declares all currently
> > ongoing accesses done. That means oom reaper would have to block/wait
> > and that is something I would really like to prevent from because it
> > just adds another possibility of the lockup (say the get_user cannot
> > make forward progress because it is stuck in the page fault allocating
> > memory). Or do you see any other way how to implement such a callback
> > mechanism without blocking on the oom_reaper side?
> 
> I'll think it over and respond.

ping?
-- 
Michal Hocko
SUSE Labs

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