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Thu, 17 Mar 2016 22:41:55 +0000 Subject: Re: [PATCH v2 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace() methods To: Peter Zijlstra References: <1458147733-29338-1-git-send-email-cmetcalf@mellanox.com> <1458147733-29338-2-git-send-email-cmetcalf@mellanox.com> <20160317193600.GY6344@twins.programming.kicks-ass.net> <56EB3050.3060607@mellanox.com> <20160317223821.GZ6344@twins.programming.kicks-ass.net> From: Chris Metcalf Message-ID: <56EB32A6.5090203@mellanox.com> Date: Thu, 17 Mar 2016 18:41:42 -0400 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: <20160317223821.GZ6344@twins.programming.kicks-ass.net> X-Originating-IP: [173.76.23.146] X-ClientProxiedBy: BL2PR01CA0035.prod.exchangelabs.com (10.141.66.35) To AM4PR05MB1682.eurprd05.prod.outlook.com (25.165.245.153) X-MS-Office365-Filtering-Correlation-Id: d0c83209-e8d4-4b33-7fc5-08d34eb558a0 X-Microsoft-Exchange-Diagnostics: 1; AM4PR05MB1682; 2:v60GfONX0u7wq7YblIoT01/RvFwplmHCR5kJSG8CVstgz5rMdPxb4WOyQz4B70QCM/JTlmFdLczee+TIn5cZh6UZjHVoENyssi60indg3YM5B0ClRE0aCbLaAIILi6BrQqbDxIreZKCehaOQj7TcVEAg5MzeOiWPczEEMMp4ysGaBALcSiPsAFNC0t+c6Uma; 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AM4PR05MB1682; 5:t3Az0Mal1HPY+bPQWHUU9KR9HQPrAqYSWwpm/88KBivM0l2ktqVTIP+XvrIh4xjPhwk01SWaLK822XjO5K0RVe9Nwejzz8VUzt1V/F+tgzB9VfRGV9jH/1buHG6QsJlp//Pmnxt+PgY6mGgieENiWA==; 24:JfvFU0quO3b2pAPDuW9eyn7q1WmLHP1MrUt773pDqTiz/81JTN6rdbS7kLZBZUzytUgur6Lu5BrLii+I+Hr9W97fYGm2JZtICurvLRT7psw= SpamDiagnosticOutput: 1:23 SpamDiagnosticMetadata: NSPM X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Mar 2016 22:41:55.5925 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM4PR05MB1682 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160317_154221_137746_22386CFD X-CRM114-Status: GOOD ( 10.03 ) X-Spam-Score: -2.0 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrew Morton , Daniel Thompson , Russell King , x86@kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , Aaron Tomlin , Thomas Gleixner , Paul McKenney , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-3.3 required=5.0 tests=BAD_ENC_HEADER,BAYES_00, DKIM_SIGNED, RCVD_IN_DNSWL_MED, RDNS_NONE, T_DKIM_INVALID, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On 3/17/2016 6:38 PM, Peter Zijlstra wrote: > On Thu, Mar 17, 2016 at 06:31:44PM -0400, Chris Metcalf wrote: >> On 3/17/2016 3:36 PM, Peter Zijlstra wrote: >>> On Wed, Mar 16, 2016 at 01:02:10PM -0400, Chris Metcalf wrote: >>>> Currently you can only request a backtrace of either all cpus, or >>>> all cpus but yourself. It can also be helpful to request a remote >>>> backtrace of a single cpu, and since we want that, the logical >>>> extension is to support a cpumask as the underlying primitive. >>>> >>>> This change modifies the existing lib/nmi_backtrace.c code to take >>>> a cpumask as its basic primitive, and modifies the linux/nmi.h code >>>> to use either the old "all/all_but_self" arch methods, or the new >>>> "cpumask" method, depending on which is available. >>>> >>>> The existing clients of nmi_backtrace (arm and x86) are converted >>>> to using the new cpumask approach in this change. >>> So the past days I've been staring at RCU stall warns, and they can use >>> a little of this. Their remote stack unwinds are less than useful. >> Were you suggesting this as an improvement for a possible v3, or just a >> kind of implicit ack of the patch series? Thanks! > A suggestion more like. I've not actually looked at the 4th patch. > > I'll try and fold the patches into the runs I do tomorrow, I'm sure to > trigger lots of fail. Maybe I'll even do that RCU patch. The build bot caught the fact that I missed arch/xtensa since it doesn't use LOCK_TEXT, so if you're testing on that (ok maybe unlikely) you can add this: diff --git a/arch/xtensa/kernel/vmlinux.lds.S b/arch/xtensa/kernel/vmlinux.lds.S index c417cbe4ec87..18a174c7fb87 100644 --- a/arch/xtensa/kernel/vmlinux.lds.S +++ b/arch/xtensa/kernel/vmlinux.lds.S @@ -93,6 +93,9 @@ SECTIONS VMLINUX_SYMBOL(__sched_text_start) = .; *(.sched.literal .sched.text) VMLINUX_SYMBOL(__sched_text_end) = .; + VMLINUX_SYMBOL(__cpuidle_text_start) = .; + *(.cpuidle.literal .cpuidle.text) + VMLINUX_SYMBOL(__cpuidle_text_end) = .; VMLINUX_SYMBOL(__lock_text_start) = .; *(.spinlock.literal .spinlock.text) VMLINUX_SYMBOL(__lock_text_end) = .;