From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79BF4C43441 for ; Wed, 14 Nov 2018 11:32:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 40D342243E for ; Wed, 14 Nov 2018 11:32:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 40D342243E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732208AbeKNVez (ORCPT ); Wed, 14 Nov 2018 16:34:55 -0500 Received: from mx2.suse.de ([195.135.220.15]:56350 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727598AbeKNVez (ORCPT ); Wed, 14 Nov 2018 16:34:55 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 76B1AAF76; Wed, 14 Nov 2018 11:32:01 +0000 (UTC) Date: Wed, 14 Nov 2018 12:31:59 +0100 From: Michal Hocko To: Chanho Min Cc: "Rafael J. Wysocki" , Pavel Machek , Len Brown , Andrew Morton , "Eric W. Biederman" , Christian Brauner , Oleg Nesterov , Anna-Maria Gleixner , Alexander Viro , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Seungho Park , Inkyu Hwang , Donghwan Jung , Jongsung Kim Subject: Re: [PATCH v2] exec: make de_thread() freezable Message-ID: <20181114113159.GR23419@dhcp22.suse.cz> References: <1541994885-20059-1-git-send-email-chanho.min@lge.com> <20181113145339.GD16182@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181113145339.GD16182@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 13-11-18 15:53:39, Michal Hocko wrote: > On Mon 12-11-18 12:54:45, Chanho Min wrote: > > Suspend fails due to the exec family of functions blocking the freezer. > > The casue is that de_thread() sleeps in TASK_UNINTERRUPTIBLE waiting for > > all sub-threads to die, and we have the deadlock if one of them is frozen. > > This also can occur with the schedule() waiting for the group thread leader > > to exit if it is frozen. > > > > In our machine, it causes freeze timeout as bellows. > > > > Freezing of tasks failed after 20.010 seconds (1 tasks refusing to freeze, wq_busy=0): > > setcpushares-ls D ffffffc00008ed70 0 5817 1483 0x0040000d > > Call trace: > > [] __switch_to+0x88/0xa0 > > [] __schedule+0x1bc/0x720 > > [] schedule+0x40/0xa8 > > [] flush_old_exec+0xdc/0x640 > > [] load_elf_binary+0x2a8/0x1090 > > [] search_binary_handler+0x9c/0x240 > > [] load_script+0x20c/0x228 > > [] search_binary_handler+0x9c/0x240 > > [] do_execveat_common.isra.14+0x4f8/0x6e8 > > [] compat_SyS_execve+0x38/0x48 > > [] el0_svc_naked+0x24/0x28 > > > > To fix this, make de_thread() freezable. It looks safe and works fine. > > It's been some time since I have looked into this code so bear with me. > One thing is not really clear to me. Why does it help to exclude this > particular task from the freezer when it is not sleeping in the freezer. > I can see how other threads need to be zapped and TASK_WAKEKILL doesn't > do that but shouldn't we fix that instead? > > Or maybe I am missing something important here. Just to not distract from the quick fix. This will silence the freezer but I believe that we need a better fix to not block exec by freezer long term. It seems much more complicated though so a quick fix makes some sense for now. Acked-by: Michal Hocko -- Michal Hocko SUSE Labs