From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752377AbcCNQju (ORCPT ); Mon, 14 Mar 2016 12:39:50 -0400 Received: from mail-wm0-f43.google.com ([74.125.82.43]:32921 "EHLO mail-wm0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752302AbcCNQjp (ORCPT ); Mon, 14 Mar 2016 12:39:45 -0400 Date: Mon, 14 Mar 2016 17:39:43 +0100 From: Michal Hocko To: "Michael S. Tsirkin" Cc: Vladimir Davydov , Andrew Morton , Tetsuo Handa , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] exit: clear TIF_MEMDIE after exit_task_work Message-ID: <20160314163943.GE11400@dhcp22.suse.cz> References: <1456765329-14890-1-git-send-email-vdavydov@virtuozzo.com> <20160301155212.GJ9461@dhcp22.suse.cz> <20160301175431-mutt-send-email-mst@redhat.com> <20160301160813.GM9461@dhcp22.suse.cz> <20160301182027-mutt-send-email-mst@redhat.com> <20160301163537.GO9461@dhcp22.suse.cz> <20160301184046-mutt-send-email-mst@redhat.com> <20160301171758.GP9461@dhcp22.suse.cz> <20160301191906-mutt-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160301191906-mutt-send-email-mst@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 01-03-16 19:20:24, Michael S. Tsirkin wrote: > On Tue, Mar 01, 2016 at 06:17:58PM +0100, Michal Hocko wrote: [...] > > Sorry, I could have been more verbose... The code would have to make sure > > that the mm is still alive before calling g-u-p by > > atomic_inc_not_zero(&mm->mm_users) and fail if the user count dropped to > > 0 in the mean time. See how fs/proc/task_mmu.c does that (proc_mem_open > > + m_start + m_stop. > > > > The biggest advanatage would be that the mm address space pin would be > > only for the particular operation. Not sure whether that is possible in > > the driver though. Anyway pinning the mm for a potentially unbounded > > amount of time doesn't sound too nice. > > Hmm that would be another atomic on data path ... > I'd have to explore that. Did you have any chance to look into this? -- Michal Hocko SUSE Labs