From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030672AbbD1Rwt (ORCPT ); Tue, 28 Apr 2015 13:52:49 -0400 Received: from mail-db3on0098.outbound.protection.outlook.com ([157.55.234.98]:19232 "EHLO emea01-db3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1030339AbbD1Rwr (ORCPT ); Tue, 28 Apr 2015 13:52:47 -0400 Authentication-Results: infradead.org; dkim=none (message not signed) header.d=none; Message-ID: <553FC8DF.7030101@ezchip.com> Date: Tue, 28 Apr 2015 13:52:31 -0400 From: Chris Metcalf User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Ulrich Obergfell CC: Frederic Weisbecker , Don Zickus , Ingo Molnar , Andrew Morton , Andrew Jones , chai wen , Fabian Frederick , Aaron Tomlin , Ben Zhang , Christoph Lameter , Gilad Ben-Yossef , Steven Rostedt , , Jonathan Corbet , , Thomas Gleixner , Peter Zijlstra Subject: Re: [PATCH v8 2/3] watchdog: add watchdog_cpumask sysctl to assist nohz References: <20150413215423.GA6121@lerouge> <1429040253-7054-1-git-send-email-cmetcalf@ezchip.com> <1429040253-7054-2-git-send-email-cmetcalf@ezchip.com> <755157528.1109591.1429181212104.JavaMail.zimbra@redhat.com> <5531299C.60600@ezchip.com> <2132240307.4651379.1429690855807.JavaMail.zimbra@redhat.com> In-Reply-To: <2132240307.4651379.1429690855807.JavaMail.zimbra@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [12.216.194.146] X-ClientProxiedBy: BN1PR12CA0038.namprd12.prod.outlook.com (25.160.77.48) To DB5PR02MB0776.eurprd02.prod.outlook.com (25.161.243.147) X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:DB5PR02MB0776; X-Forefront-Antispam-Report: BMV:1;SFV:NSPM;SFS:(10009020)(979002)(6049001)(6009001)(377454003)(51704005)(76104003)(24454002)(479174004)(52604005)(33656002)(83506001)(4001350100001)(46102003)(42186005)(80316001)(92566002)(87976001)(36756003)(86362001)(40100003)(93886004)(62966003)(65806001)(50986999)(47776003)(77156002)(110136001)(81156007)(59896002)(77096005)(2950100001)(54356999)(122386002)(76176999)(65956001)(23676002)(50466002)(15975445007)(65816999)(87266999)(19580395003)(66066001)(64126003)(18886065003)(969003)(989001)(999001)(1009001)(1019001);DIR:OUT;SFP:1101;SCL:1;SRVR:DB5PR02MB0776;H:[10.7.0.41];FPR:;SPF:None;MLV:ovrnspm;PTR:InfoNoRecords;LANG:en; X-Microsoft-Antispam-PRVS: X-Exchange-Antispam-Report-Test: UriScan:; X-Exchange-Antispam-Report-CFA-Test: BCL:0;PCL:0;RULEID:(601004)(5002010)(5005006)(3002001);SRVR:DB5PR02MB0776;BCL:0;PCL:0;RULEID:;SRVR:DB5PR02MB0776; X-Forefront-PRVS: 0560A2214D X-OriginatorOrg: ezchip.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Apr 2015 17:52:42.1323 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB5PR02MB0776 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/22/2015 04:20 AM, Ulrich Obergfell wrote: > Chris, > > in principle the change looks o.k. to me, even though I'm not really familiar > with the watchdog_nmi_disable_all() and watchdog_nmi_enable_all() functions. > It is my understanding that those functions are only called once via 'initcall' > early during kernel startup as shown in the following flow of execution: > > [...] > It seems crucial that lockup_detector_init() is executed before fixup_ht_bug(). Uli, thanks for doing the follow-up analysis. I didn't know about the fixup_ht_bug() path, but as you show, it seems to be OK. We could think about doing some kind of additional paranoia here, like a wrapper around &watchdog_cpumask that checks some additional boolean that says whether it's been properly initialized or not. But I think it's probably OK to leave it as-is; we already had the potential of issues if any watchdog code was invoked prior to init_watchdog(), for example due to the sample period being unset. What do you think? -- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com