Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752282AbaDYQpg (ORCPT ); Fri, 25 Apr 2014 12:45:36 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.228]:51173 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751231AbaDYQpe (ORCPT ); Fri, 25 Apr 2014 12:45:34 -0400 Date: Fri, 25 Apr 2014 12:45:30 -0400 From: Steven Rostedt To: Daniel Thompson Cc: kgdb-bugreport@lists.sourceforge.net, Jason Wessel , patches@linaro.org, linaro-kernel@lists.linaro.org, linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Jiri Slaby , Frederic Weisbecker , Ingo Molnar , John Stultz , Anton Vorontsov , Colin Cross , kernel-team@android.com Subject: Re: [RFC v3 1/9] sysrq: Implement __handle_sysrq_nolock to avoid recursive locking in kdb Message-ID: <20140425124530.52fd696c@gandalf.local.home> In-Reply-To: <1398443370-12668-2-git-send-email-daniel.thompson@linaro.org> References: <1396453440-16445-1-git-send-email-daniel.thompson@linaro.org> <1398443370-12668-1-git-send-email-daniel.thompson@linaro.org> <1398443370-12668-2-git-send-email-daniel.thompson@linaro.org> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.130:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 25 Apr 2014 17:29:22 +0100 Daniel Thompson wrote: > If kdb is triggered using SysRq-g then any use of the sr command results > in the SysRq key table lock being recursively acquired, killing the debug > session. That patch resolves the problem by introducing a _nolock > alternative for __handle_sysrq. > > Strictly speaking this approach risks racing on the key table when kdb is > triggered by something other than SysRq-g however in that case any other > CPU involved should release the spin lock before kgdb parks the slave > CPUs. Is that case documented somewhere in the code comments? -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/