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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 DDA30C04EB9 for ; Mon, 3 Dec 2018 12:03:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AEE4C2087F for ; Mon, 3 Dec 2018 12:03:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AEE4C2087F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net 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 S1726429AbeLCMEN (ORCPT ); Mon, 3 Dec 2018 07:04:13 -0500 Received: from cloudserver094114.home.pl ([79.96.170.134]:59144 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725883AbeLCMEM (ORCPT ); Mon, 3 Dec 2018 07:04:12 -0500 Received: from 79.184.252.87.ipv4.supernova.orange.pl (79.184.252.87) (HELO aspire.rjw.lan) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.157) id 8a403304dd5b4437; Mon, 3 Dec 2018 13:03:25 +0100 From: "Rafael J. Wysocki" To: Michal Hocko Cc: Ingo Molnar , Linus Torvalds , Linux List Kernel Mailing , "Rafael J. Wysocki" , Chanho Min , Thomas Gleixner , Peter Zijlstra , Oleg Nesterov , Pavel Machek Subject: Re: [PATCH] Revert "exec: make de_thread() freezable (was: Re: Linux 4.20-rc4) Date: Mon, 03 Dec 2018 13:03:16 +0100 Message-ID: <1718869.PGhsHE7EHz@aspire.rjw.lan> In-Reply-To: <20181203083942.GF31738@dhcp22.suse.cz> References: <20181203074700.GA21240@gmail.com> <20181203083942.GF31738@dhcp22.suse.cz> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, December 3, 2018 9:39:42 AM CET Michal Hocko wrote: > On Mon 03-12-18 08:47:00, Ingo Molnar wrote: > [...] > > I reviewed the ->cred_guard_mutex code, and the mutex is held across all > > of exec() - and we always did this. > > Yes, this is something that has been pointed out during the review. Oleg > has argued that making this path freezable is really hard and that we > should be changing de_thread to sleep withtou cred_guard_mutex long term > anyway (http://lkml.kernel.org/r/20181114143705.GB13885@redhat.com). > > Failing suspend seems like a real problem while the lockdep one doesn't > really reflect any real deadlock, right? So while the patch is not > perfect it shouldn't make the situation much worse. Lockdep splat is > certainly annoying but is it any worse than a suspend failing? > > Now, I wouldn't mind to revert this because the code is really old and > we haven't seen many bug reports about failing suspend yet. But what is > the actual plan to make this work properly? Use > freezable_schedule_unsafe instead? Freezer code has some > fundamental design issues which are quite hard to get over. I agree and we just need to look deeper into this. I had hoped that this would work since you and Oleg agreed with it, but since it doesn't, let's do a revert for now and get back to this later. Thanks, Rafael