From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966957AbcAZRWy (ORCPT ); Tue, 26 Jan 2016 12:22:54 -0500 Received: from mail-am1on0063.outbound.protection.outlook.com ([157.56.112.63]:13126 "EHLO emea01-am1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966830AbcAZRWu (ORCPT ); Tue, 26 Jan 2016 12:22:50 -0500 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=cmetcalf@ezchip.com; Subject: Re: [PATCH v2] Add hard/soft lockup debugger entry points To: Jeff Merkey , References: <20160126170454.GA28216@localhost.localdomain> CC: Andrew Morton , Don Zickus , Ulrich Obergfell , Aaron Tomlin , Michal Hocko , Frederic Weisbecker , Tejun Heo , Hidehiro Kawai From: Chris Metcalf Message-ID: <56A7AB5B.2000000@ezchip.com> Date: Tue, 26 Jan 2016 12:22:35 -0500 User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20160126170454.GA28216@localhost.localdomain> Content-Type: text/plain; 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X-Microsoft-Exchange-Diagnostics: =?Windows-1252?Q?1;DB4PR02MB127;23:OHpuCdVaQFuBKYIAB2Qp/czr20CbUzL2Ja02gS?= =?Windows-1252?Q?KYyDLFC4tDqR0RPK1chVXPNo51IQQLbRKCQaeuZBWw6VldWE0S9cufWA?= =?Windows-1252?Q?Q2+zfQ76fTGcMecGSCxxP2jnTMBpW6Vti9CeQ4sgq3+WF/+uiMxyaYYT?= =?Windows-1252?Q?OqNT3BeJUrcLAl0gR5RY6kNo5WJLLhE1GZuz0CytJZLtASh1pyNx2MVj?= =?Windows-1252?Q?KqeoC5eGu3vSoKoPelwlTWU7OI/MTxyx7HELtS/rW4Scm9i0u5XfnM2k?= =?Windows-1252?Q?7QIAAxoniaakrNCwEiuwuFkW9LZMbN3rUSVs4Fid7pvvMP19es2YpwYn?= =?Windows-1252?Q?/rILLJGInTC9Lj62wn3vOQ1n+wvZ2PaSUqfo3y8iE6ghD8Y6mqVxJiwk?= =?Windows-1252?Q?27u0kR1HrX+sTag2ESGwWnEiuMXzrtSjsbB5/M1ayyaaOZCSNqJvispG?= =?Windows-1252?Q?PKxE39oreDJPdGEgEWswxLaRWdxNPV4WFUQJ/klSwAuTG9NEKrbL3sVR?= =?Windows-1252?Q?6ddafmbaz0YQI8i3If9KmVukT1PKNVZ+cT9It1GGuRc42Q6JdDF7i/Ni?= =?Windows-1252?Q?wVTfgxLB+pCyRS1z1r4TGZRSBTSeoEcobURYhM07HY2s2Bf5xkXAgB9o?= =?Windows-1252?Q?1YTRG+kS3Uk/B0EbltFmT7MkwrhUI7LXjZXlKCQm+Rs62fyM3NMPoWmn?= =?Windows-1252?Q?zLfjaE1ndPMqxCSBOVW+f6prleFDOWSNhkWd3wux/bz7YkN3LtvWBV5I?= =?Windows-1252?Q?mG2jURNoOc/3OL+VTfuzVbJk5TO96bvABtXak5rDu7S7QzeC0aks9YjB?= =?Windows-1252?Q?40Qi64mee+1xHcyMLcllw/IN8z2eV1FugrhvoEtxeagInWMiRfDPsE7K?= =?Windows-1252?Q?T2hybqYpw+F/5gq5GRrxelh25wLGiYTm4gvyusd64L8NdZxIWvR81N4I?= =?Windows-1252?Q?yVBQ8iTQxk8NcMQdwTghQ15r+ZOBPeTHx2EvyBLQdMg6kvVpvOrVgWRR?= =?Windows-1252?Q?u3JiRUuHGecWP5aH21xUbJ6ZPZqLduQZ7G4HgTJfLKd2tUxJ7KD7JixM?= =?Windows-1252?Q?8puS/Y0k4vd8vQzingUTV3fzQTteuu1BcNwbgzUonxnbqQnEsJKbL/fI?= =?Windows-1252?Q?2e9W3l2RODPmMAUrSkShxyfsu0vyDiXiGfB7Dj7UoVAIwB4Vb3CSoyrh?= =?Windows-1252?Q?i1DB1nevIScjecXYxbuPB4vz4n/dW2F7g82fucDlyUnlxsCa7r0SKoCD?= =?Windows-1252?Q?Un8T/hEaY1HBwlBaj1eFAjm6fjByLluGpeFD9CF4RmGZwlxzYl8fLNPX?= =?Windows-1252?Q?dByxCPbtb+/VPIHJElBPt/sjKD5fP25ttM/H13PDXmOGdSDqZHkOEITZ?= =?Windows-1252?Q?4fjK9gWFy7OpCFMaUlg4j2NaFJRatmeLzzk8P5QdQ12QLbsXooGEGKg9?= =?Windows-1252?Q?qcAa0BtxMCGuSMifTicdkD//1+p7wFv8U39J0Z3oAfQ42g5jf/LIRroI?= =?Windows-1252?Q?/whGfivp7Ch295FYGqSy0BTR4R?= X-Microsoft-Exchange-Diagnostics: 1;DB4PR02MB127;5:mwqvwVaE4Qmhyf8XKPfQhZOr9vNJ81SL/F7Xbq4CnUvY+DQSv/NjOwuxcRvKSWiKw+CG7ouMA1dA+0Os+suwCOSJXxIbWP8LO2pxRIKsEYhBf8fXx9RXUTTjoCeHrGHj/IOLgrublVvn2nvjSsFgxA==;24:Jmf5Mbxx/ChJtgPUhkfnrLOObd90tIcLnGTy7iOmxoqY+30mGp1fMIDr+aNFjvFOs0ccrWPdCJt5BuHimOtU4HVMZv3pJX9DhPnFQe5SFQ4= SpamDiagnosticOutput: 1:23 SpamDiagnosticMetadata: NSPM X-OriginatorOrg: ezchip.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Jan 2016 17:22:45.4087 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB4PR02MB127 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/26/2016 12:04 PM, Jeff Merkey wrote: > This patch adds an export which can be set by system debuggers to direct > the hard lockup and soft lockup detector to trigger a breakpoint exception > and enter a debugger if one is active. It is assumed that if someone > sets this variable, then an breakpoint handler of some sort will be actively > loaded or registered via the notify die handler chain. > > This addition is extremely useful for debugging hard and soft lockups > real time and quickly from a console debugger. > > Signed-off-by: Jeff Merkey > --- > kernel/watchdog.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) You probably should reach out to someone who uses this stuff more regularly - I actually wonder if the kgdb_breakpoint() API is the right thing, though, not the internal arch_kgdb_breakpoint(). Of course any of these strategies also assume you are building the kernel with CONFIG_KGDB set, and I'm pretty sure will cause your build to fail if it isn't. You likely need to guard this stuff locally within watchdog.c for !CONFIG_KGDB. -- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com