Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756626AbcLRQGN (ORCPT ); Sun, 18 Dec 2016 11:06:13 -0500 Received: from mail-wj0-f194.google.com ([209.85.210.194]:33383 "EHLO mail-wj0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754247AbcLRQGM (ORCPT ); Sun, 18 Dec 2016 11:06:12 -0500 Date: Sun, 18 Dec 2016 17:06:08 +0100 From: Michal Hocko To: Tetsuo Handa Cc: "Kirill A. Shutemov" , Vegard Nossum , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rik van Riel , Matthew Wilcox , Peter Zijlstra , Andrew Morton , Al Viro , Ingo Molnar , Linus Torvalds Subject: Re: crash during oom reaper Message-ID: <20161218160608.GA8440@dhcp22.suse.cz> References: <20161216090157.GA13940@dhcp22.suse.cz> <20161216101113.GE13940@dhcp22.suse.cz> <20161216104438.GD27758@node> <20161216114243.GG13940@dhcp22.suse.cz> <20161216123555.GE27758@node> <20161216125650.GJ13940@dhcp22.suse.cz> <20161216130730.GF27758@node> <20161216131427.GM13940@dhcp22.suse.cz> <7918aa6b-8517-956b-5258-616ef1df6338@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7918aa6b-8517-956b-5258-616ef1df6338@I-love.SAKURA.ne.jp> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1428 Lines: 35 On Sun 18-12-16 22:47:07, Tetsuo Handa wrote: > On 2016/12/16 22:14, Michal Hocko wrote: [...] > > I would have to rememeber all the details. This is mostly off-topic for > > this particular thread so I think it would be better if you could send a > > full patch separatelly and we can discuss it there? > > > > zap_page_range() calls mmu_notifier_invalidate_range_start(). > mmu_notifier_invalidate_range_start() calls __mmu_notifier_invalidate_range_start(). > __mmu_notifier_invalidate_range_start() calls srcu_read_lock()/srcu_read_unlock(). > This means that zap_page_range() might sleep. > > I don't know what individual notifier will do, but for example > > static const struct mmu_notifier_ops i915_gem_userptr_notifier = { > .invalidate_range_start = i915_gem_userptr_mn_invalidate_range_start, > }; > > i915_gem_userptr_mn_invalidate_range_start() calls flush_workqueue() > which means that we can OOM livelock if work item involves memory allocation. > Some of other notifiers call mutex_lock()/mutex_unlock(). > > Even if none of currently in-tree notifier users are blocked on memory > allocation, I think it is not guaranteed that future changes/users won't be > blocked on memory allocation. Kirill has sent this as a separate patchset [1]. Could you follow up on that there please? http://lkml.kernel.org/r/20161216141556.75130-4-kirill.shutemov@linux.intel.com -- Michal Hocko SUSE Labs