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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 35B72C4CECD for ; Tue, 17 Sep 2019 17:38:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18ABB2171F for ; Tue, 17 Sep 2019 17:38:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731294AbfIQRic (ORCPT ); Tue, 17 Sep 2019 13:38:32 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:59377 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725976AbfIQRib (ORCPT ); Tue, 17 Sep 2019 13:38:31 -0400 Received: from in01.mta.xmission.com ([166.70.13.51]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1iAHQo-0005xA-Ok; Tue, 17 Sep 2019 11:38:26 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1iAHQn-0001k7-Ob; Tue, 17 Sep 2019 11:38:26 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Linus Torvalds Cc: Peter Zijlstra , Oleg Nesterov , Russell King - ARM Linux admin , Chris Metcalf , Christoph Lameter , Kirill Tkhai , Mike Galbraith , Thomas Gleixner , Ingo Molnar , Linux List Kernel Mailing , Davidlohr Bueso , "Paul E. McKenney" References: <20190830140805.GD13294@shell.armlinux.org.uk> <20190830160957.GC2634@redhat.com> <87o906wimo.fsf@x220.int.ebiederm.org> <20190902134003.GA14770@redhat.com> <87tv9uiq9r.fsf@x220.int.ebiederm.org> <87k1aqt23r.fsf_-_@x220.int.ebiederm.org> <87muf7f4bf.fsf_-_@x220.int.ebiederm.org> Date: Tue, 17 Sep 2019 12:38:04 -0500 In-Reply-To: (Linus Torvalds's message of "Sat, 14 Sep 2019 10:43:59 -0700") Message-ID: <8736gu962r.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1iAHQn-0001k7-Ob;;;mid=<8736gu962r.fsf@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/RFHzV/wcSYCSYXdS/J/heIs1ylgpLA98= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v2 0/4] task: Making tasks on the runqueue rcu protected X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus Torvalds writes: > On Sat, Sep 14, 2019 at 5:30 AM Eric W. Biederman wrote: >> >> I have reworked these patches one more time to make it clear that the >> first 3 patches only fix task_struct so that it experiences a rcu grace >> period after it leaves the runqueue for the last time. > > I remain a fan of these patches, and the added comment on the last one > is I think a sufficient clarification of the issue. > > But it's patch 3 that makes me go "yeah, this is the right approach", > because it just removes subtle code in favor of something that is > understandable. > > Yes, most of the lines removed may be comments, and so it doesn't > actually remove a lot of _code_, but I think the comments are a result > of just how subtle and fragile our current approach is, and the new > model not needing them as much is I think a real issue (rather than > just Eric being less verbose in the new comments and removing lines of > code that way). In fact the comments I add are orthogonal to the comments I removed. My last patch stands on it's own. It can be applied with or without the rest. I just needed to know which of the ordinary rcu guarantees were or were not present in the code. > Can anybody see anything wrong with the series? Because I'd love to > have it for 5.4, Peter, I am more than happy for these to come through your tree. However if this is one thing to many I will be happy to send Linus a pull request myself early next week. Eric