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 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 2F382C83004 for ; Tue, 28 Apr 2020 18:58:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 05F0320730 for ; Tue, 28 Apr 2020 18:58:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730070AbgD1S6F (ORCPT ); Tue, 28 Apr 2020 14:58:05 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:39868 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728934AbgD1S6A (ORCPT ); Tue, 28 Apr 2020 14:58:00 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jTVQc-00065Q-TV; Tue, 28 Apr 2020 12:57:58 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jTVQc-00082d-3W; Tue, 28 Apr 2020 12:57:58 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Oleg Nesterov Cc: Linus Torvalds , LKML , Linux FS Devel , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Alexey Gladkov , Thomas Gleixner , "Paul E. McKenney" References: <20200419141057.621356-1-gladkov.alexey@gmail.com> <87ftcv1nqe.fsf@x220.int.ebiederm.org> <87wo66vvnm.fsf_-_@x220.int.ebiederm.org> <20200424173927.GB26802@redhat.com> <87mu6ymkea.fsf_-_@x220.int.ebiederm.org> <875zdmmj4y.fsf_-_@x220.int.ebiederm.org> <878sihgfzh.fsf@x220.int.ebiederm.org> <87sggnajpv.fsf_-_@x220.int.ebiederm.org> <20200428180540.GB29960@redhat.com> Date: Tue, 28 Apr 2020 13:54:43 -0500 In-Reply-To: <20200428180540.GB29960@redhat.com> (Oleg Nesterov's message of "Tue, 28 Apr 2020 20:05:41 +0200") Message-ID: <875zdj8mq4.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=1jTVQc-00082d-3W;;;mid=<875zdj8mq4.fsf@x220.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18ie873QmSJRuG7xLnHvzMNPbq5XK7pRSI= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v4 0/2] proc: Ensure we see the exit of each process tid exactly X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg Nesterov writes: > On 04/28, Eric W. Biederman wrote: >> >> In short I don't think this change will introduce any regressions. >> >> Eric W. Biederman (2): >> rculist: Add hlists_swap_heads_rcu >> proc: Ensure we see the exit of each process tid exactly once > > Eric, sorry, I got lost. > > Both changes look good to me, feel free to add my ack, but I presume > this is on top of next_tgid/lookup_task changes ? If yes, why did not > you remove has_group_leader_pid? On top of next_tgid. Upon a close examination there are not any current bugs in posix-cpu-timers nor is there anything that exchange_tids will make worse. I am preparing a follow on patchset to kill has_group_leader_pid. I am preparing a further follow on patchset to see if I can get that code to start returning pids, because that is cheaper and clearer. I pushed those changes a little farther out so I could maintain focus on what I am accomplishing. Adding exchange_tids was difficult because I had to audit pretty much all of the pid use in the kernel to see if the small change in behavior would make anything worse. The rest of the changes should be simpler and more localized so I hope they go faster. Eric