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b=Lyk7My1y+11V5b1piWTM6hzh51rsYiRoOXe5U2bTgD3Nfb1rxh6uqc0COSLfoEMkj3tT8n ra65v9iCoQtVkfsDsyBL9+FEwTK6Ky6IaabQOJVEvDALvwrH/7vz8H6mm++orXhg+5jOoY /mGAabSUdlRNqITfMmRFhr5+lLmv48I= Received: from suse.cz (unknown [10.100.208.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 2DAA62C146; Wed, 5 Apr 2023 08:53:12 +0000 (UTC) Date: Wed, 5 Apr 2023 10:53:11 +0200 From: Petr Mladek To: Michal Hocko Cc: Andrew Morton , Tetsuo Handa , Patrick Daly , Mel Gorman , David Hildenbrand , Sergey Senozhatsky , Steven Rostedt , John Ogness , syzkaller-bugs@googlegroups.com, Ilpo =?iso-8859-1?Q?J=E4rvinen?= , syzbot , linux-mm Subject: Re: [PATCH v2] mm/page_alloc: fix potential deadlock on zonelist_update_seq seqlock Message-ID: References: <6266b161-e4c3-7d65-6590-da6cc04d93ec@I-love.SAKURA.ne.jp> <0585ddb9-5de8-8cdd-202e-53887bbb6b5f@I-love.SAKURA.ne.jp> <8796b95c-3da3-5885-fddd-6ef55f30e4d3@I-love.SAKURA.ne.jp> <20230404142528.d232bcdc59ac9cf11de10580@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: q7eashsqkh83h3fn6st74so9intzp14z X-Rspamd-Queue-Id: 73902160008 X-HE-Tag: 1680684795-687557 X-HE-Meta: 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 yrdhbY39 g9QW3fuqKxjhbB6pAu3Uw1HkvBUXDKJScPsznRY2rDWct2pS5lW5vNxLkoIFuqQfBYCR2aAPBNZlsLFBzha9KNGPM/WwP9JtxRKNYA96bfA54+H+vGrPvPs1sO2PAVZlabP7X9fu6vmlDOt7ol6TpPwssM5vPvXFzrVeenjv2zCxlvElZBbZDXVyeEqKiNiO2m8gyrMo1C48bZQBrdYQ63lyTFl2YTaer/Fmun+fgFoGIeDazjbN5jkSr2Y+8RAuvJUOyAkaIZfo8bgG3LCrctc9uYxFpQq/9ZHf2WhQjiG/IoUPXkOkF2HoSpA== 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 2023-04-05 10:28:07, Michal Hocko wrote: > On Tue 04-04-23 14:25:28, Andrew Morton wrote: > > On Tue, 4 Apr 2023 23:31:58 +0900 Tetsuo Handa wrote: > > > > > syzbot is reporting circular locking dependency which involves > > > zonelist_update_seq seqlock [1], for this lock is checked by memory > > > allocation requests which do not need to be retried. > > > > I queued this, along with a note that an updated changelog is likely. > > > > Do we feel that a -stable backport is warranted? I think so, from your > > earlier comments. Please add the cc:stable to the changelog in this > > situation. > > Memory hotplug is pretty rare event so the deadlock is quite unlikely. > On the other hand the fix is pretty easy so it shouldn't hurt to have it > in stable kernels. Note that printk_deferred_enter()/exit() has been added in v5.15-rc1 by the commit 85e3e7fbbb720b9897 ("printk: remove NMI tracking"). The commit has non-trivial dependencies. Any backport for older stable kernel would need a custom patch just adding these two wrappers. Best Regards, Petr