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[37.188.180.223]) by smtp.gmail.com with ESMTPSA id a82sm6434836wmh.0.2020.04.01.09.26.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2020 09:26:57 -0700 (PDT) Date: Wed, 1 Apr 2020 18:26:55 +0200 From: Michal Hocko To: Daniel Jordan , Vlastimil Babka Cc: David Hildenbrand , Shile Zhang , Andrew Morton , Kirill Tkhai , Pavel Tatashin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm: fix tick timer stall during deferred page init Message-ID: <20200401162655.GX22681@dhcp22.suse.cz> References: <20200311123848.118638-1-shile.zhang@linux.alibaba.com> <20200401154217.GQ22681@dhcp22.suse.cz> <20200401160048.GU22681@dhcp22.suse.cz> <20200401160929.jwekhr24tb44odea@ca-dmjordan1.us.oracle.com> <20200401161243.GW22681@dhcp22.suse.cz> <20200401161810.xvqikca2x46yqrlx@ca-dmjordan1.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200401161810.xvqikca2x46yqrlx@ca-dmjordan1.us.oracle.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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