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Date:   Wed, 1 Apr 2020 18:26:55 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     Daniel Jordan <daniel.m.jordan@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>
Cc:     David Hildenbrand <david@redhat.com>,
        Shile Zhang <shile.zhang@linux.alibaba.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kirill Tkhai <ktkhai@virtuozzo.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] mm: fix tick timer stall during deferred page init
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On Wed 01-04-20 12:18:10, Daniel Jordan wrote:
> On Wed, Apr 01, 2020 at 06:12:43PM +0200, Michal Hocko wrote:
> > On Wed 01-04-20 12:09:29, Daniel Jordan wrote:
> > > On Wed, Apr 01, 2020 at 06:00:48PM +0200, Michal Hocko wrote:
> > > > On Wed 01-04-20 17:50:22, David Hildenbrand wrote:
> > > > > On 01.04.20 17:42, Michal Hocko wrote:
> > > > > > This needs a double checking but I strongly believe that the lock can be
> > > > > > simply dropped in this path.
> > > 
> > > This is what my fix does, it limits the time the resize lock is held.
> > 
> > Just remove it from the deferred intialization and add a comment that we
> > deliberately not taking the lock here because abc
> 
> I think it has to be a little more involved because of the window where
> interrupts might allocate during deferred init, as Vlastimil pointed out a few
> years ago when the change was made.

I do not remember any details but do we have any actual real allocation
failure or was this mostly a theoretical concern. Vlastimil? For your
context we are talking about 3a2d7fa8a3d5 ("mm: disable interrupts while
initializing deferred pages")

> I'll explain myself in the changelog.

OK, I will wait for the patch.
-- 
Michal Hocko
SUSE Labs