From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f177.google.com (mail-ob0-f177.google.com [209.85.214.177]) by kanga.kvack.org (Postfix) with ESMTP id C00346B0005 for ; Thu, 17 Mar 2016 11:20:49 -0400 (EDT) Received: by mail-ob0-f177.google.com with SMTP id m7so86746622obh.3 for ; Thu, 17 Mar 2016 08:20:49 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id k194si4995567oib.149.2016.03.17.08.20.47 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 17 Mar 2016 08:20:47 -0700 (PDT) Subject: Re: [PATCH 6/5] oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task From: Tetsuo Handa References: <20160317121751.GE26017@dhcp22.suse.cz> <201603172200.CIE52148.QOVSOHJFMLOFtF@I-love.SAKURA.ne.jp> <20160317132335.GF26017@dhcp22.suse.cz> <201603172334.EGD54504.OLFQVJFOtMHFOS@I-love.SAKURA.ne.jp> <20160317145433.GG26017@dhcp22.suse.cz> In-Reply-To: <20160317145433.GG26017@dhcp22.suse.cz> Message-Id: <201603180020.IGB30229.LOSFJQHtFVMOOF@I-love.SAKURA.ne.jp> Date: Fri, 18 Mar 2016 00:20:41 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@kernel.org Cc: linux-mm@kvack.org Michal Hocko wrote: > > Strictly speaking, neither debug_show_all_locks() nor debug_show_held_locks() > > are safe enough to guarantee that the system won't crash. > > > > commit 856848737bd944c1 "lockdep: fix debug_show_all_locks()" > > commit 82a1fcb90287052a "softlockup: automatically detect hung TASK_UNINTERRUPTIBLE tasks" > > > > They are convenient but we should avoid using them if we care about > > possibility of crash. > > I really fail to see your point. debug_show_all_locks doesn't mention > any restriction of the risk nor it is restricted to a particular > context. Were there some bugs in that area? Probably yes, so what? commit 856848737bd944c1 changed that locks held by TASK_RUNNING tasks are not reported. We might fail to report the task which is holding mmap_sem for write when we call debug_show_all_locks() in order to find such task. Therefore, I think guessing from sched_show_task() output can be used. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org