From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753258AbdLNOF1 (ORCPT ); Thu, 14 Dec 2017 09:05:27 -0500 Received: from mx2.suse.de ([195.135.220.15]:43824 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753222AbdLNOFG (ORCPT ); Thu, 14 Dec 2017 09:05:06 -0500 Date: Thu, 14 Dec 2017 15:05:04 +0100 From: Michal Hocko To: Linus Torvalds Cc: Andrew Morton , Will Deacon , Minchan Kim , Andrea Argangeli , Ingo Molnar , linux-mm , LKML Subject: Re: [PATCH] arch, mm: introduce arch_tlb_gather_mmu_exit Message-ID: <20171214140504.GP16951@dhcp22.suse.cz> References: <20171205145853.26614-1-mhocko@kernel.org> <20171205191410.f2rvaluftnd6dqer@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171205191410.f2rvaluftnd6dqer@dhcp22.suse.cz> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 05-12-17 20:14:37, Michal Hocko wrote: > On Tue 05-12-17 10:31:12, Linus Torvalds wrote: > > On Tue, Dec 5, 2017 at 6:58 AM, Michal Hocko wrote: > > > > > > This all is nice but tlb_gather users are not aware of that and this can > > > actually cause some real problems. E.g. the oom_reaper tries to reap the > > > whole address space but it might race with threads accessing the memory [1]. > > > It is possible that soft-dirty handling might suffer from the same > > > problem [2] as soon as it starts supporting the feature. > > > > So we fixed the oom reaper to just do proper TLB invalidates in commit > > 687cb0884a71 ("mm, oom_reaper: gather each vma to prevent leaking TLB > > entry"). > > > > So now "fullmm" should be the expected "exit" case, and it all should > > be unambiguous. > > > > Do we really have any reason to apply this patch any more? > > Well, the point was the clarity. The bad behavior came as a surprise for > the oom reaper and as Minchan mentioned we would see a similar problem > with soft-dirty bits as soon as they are supported on arm64 or > potentially other architectures which might do special handling for exit > case. I am not going to push this patch if it is considered pointless but I haven't heard back anything to the above argument. -- Michal Hocko SUSE Labs