From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id C25706B2F90 for ; Fri, 24 Aug 2018 08:03:44 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id x20-v6so3527570eda.22 for ; Fri, 24 Aug 2018 05:03:44 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id w2-v6si604994edj.389.2018.08.24.05.03.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 24 Aug 2018 05:03:43 -0700 (PDT) Date: Fri, 24 Aug 2018 14:03:39 +0200 From: Michal Hocko Subject: Re: [PATCH] mm, oom: distinguish blockable mode for mmu notifiers Message-ID: <20180824120339.GL29735@dhcp22.suse.cz> References: <20180716115058.5559-1-mhocko@kernel.org> <8cbfb09f-0c5a-8d43-1f5e-f3ff7612e289@I-love.SAKURA.ne.jp> <20180824113248.GH29735@dhcp22.suse.cz> <20180824115226.GK29735@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: christian.koenig@amd.com Cc: kvm@vger.kernel.org, Radim =?utf-8?B?S3LEjW3DocWZ?= , Tetsuo Handa , Joonas Lahtinen , Sudeep Dutt , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, Andrea Arcangeli , "David (ChunMing) Zhou" , Dimitri Sivanich , Jason Gunthorpe , linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, David Airlie , Doug Ledford , David Rientjes , xen-devel@lists.xenproject.org, intel-gfx@lists.freedesktop.org, Jani Nikula , Leon Romanovsky , =?iso-8859-1?B?Suly9G1l?= Glisse , Rodrigo Vivi , Boris Ostrovsky , Juergen Gross , Mike Marciniszyn , Dennis Dalessandro , LKML , Ashutosh Dixit , Alex Deucher , Paolo Bonzini , Andrew Morton , Felix Kuehling On Fri 24-08-18 13:57:52, Christian Konig wrote: > Am 24.08.2018 um 13:52 schrieb Michal Hocko: > > On Fri 24-08-18 13:43:16, Christian Konig wrote: [...] > > > That won't work like this there might be multiple > > > invalidate_range_start()/invalidate_range_end() pairs open at the same time. > > > E.g. the lock might be taken recursively and that is illegal for a > > > rw_semaphore. > > I am not sure I follow. Are you saying that one invalidate_range might > > trigger another one from the same path? > > No, but what can happen is: > > invalidate_range_start(A,B); > invalidate_range_start(C,D); > ... > invalidate_range_end(C,D); > invalidate_range_end(A,B); > > Grabbing the read lock twice would be illegal in this case. I am sorry but I still do not follow. What is the context the two are called from? Can you give me an example. I simply do not see it in the code, mostly because I am not familiar with it. -- Michal Hocko SUSE Labs