linux-kernel - Re: [PATCH v3] mm: fix tick timer stall during deferred page init

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Message-ID: <20200401161810.xvqikca2x46yqrlx@ca-dmjordan1.us.oracle.com>
Date:   Wed, 1 Apr 2020 12:18:10 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Daniel Jordan <daniel.m.jordan@...cle.com>,
        David Hildenbrand <david@...hat.com>,
        Shile Zhang <shile.zhang@...ux.alibaba.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm: fix tick timer stall during deferred page init

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'll explain myself in the changelog.