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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 7369FC3A59F for ; Mon, 26 Aug 2019 16:19:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4209C2173E for ; Mon, 26 Aug 2019 16:19:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732662AbfHZQTd (ORCPT ); Mon, 26 Aug 2019 12:19:33 -0400 Received: from mga09.intel.com ([134.134.136.24]:53657 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731762AbfHZQTd (ORCPT ); Mon, 26 Aug 2019 12:19:33 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Aug 2019 09:19:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,433,1559545200"; d="scan'208";a="355476615" Received: from mgross-mobl.amr.corp.intel.com (HELO localhost) ([10.7.198.58]) by orsmga005.jf.intel.com with ESMTP; 26 Aug 2019 09:19:31 -0700 Date: Mon, 26 Aug 2019 09:19:31 -0700 From: mark gross To: Vineeth Remanan Pillai Cc: Nishanth Aravamudan , Julien Desfossez , Peter Zijlstra , Tim Chen , mingo@kernel.org, tglx@linutronix.de, pjt@google.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, subhra.mazumdar@oracle.com, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Aaron Lu , Aubrey Li , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini Subject: Re: [RFC PATCH v3 01/16] stop_machine: Fix stop_cpus_in_progress ordering Message-ID: <20190826161929.GB2680@u1904> Reply-To: mgross@linux.intel.com References: <0fd8fd4b99b9b9aa88d8b2dff897f7fd0d88f72c.1559129225.git.vpillai@digitalocean.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0fd8fd4b99b9b9aa88d8b2dff897f7fd0d88f72c.1559129225.git.vpillai@digitalocean.com> 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 Wed, May 29, 2019 at 08:36:37PM +0000, Vineeth Remanan Pillai wrote: > From: Peter Zijlstra > > Make sure the entire for loop has stop_cpus_in_progress set. It is not clear how this commit comment matches the change. Please explain how adding 2 barrier's makes sure stop_cpus_in_progress is set for the entier for loop. --mark > > Signed-off-by: Peter Zijlstra (Intel) > --- > kernel/stop_machine.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c > index 067cb83f37ea..583119e0c51c 100644 > --- a/kernel/stop_machine.c > +++ b/kernel/stop_machine.c > @@ -375,6 +375,7 @@ static bool queue_stop_cpus_work(const struct cpumask *cpumask, > */ > preempt_disable(); > stop_cpus_in_progress = true; > + barrier(); > for_each_cpu(cpu, cpumask) { > work = &per_cpu(cpu_stopper.stop_work, cpu); > work->fn = fn; > @@ -383,6 +384,7 @@ static bool queue_stop_cpus_work(const struct cpumask *cpumask, > if (cpu_stop_queue_work(cpu, work)) > queued = true; > } > + barrier(); > stop_cpus_in_progress = false; > preempt_enable(); > > -- > 2.17.1 >