From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1767955AbcHROiZ (ORCPT ); Thu, 18 Aug 2016 10:38:25 -0400 Received: from mx2.suse.de ([195.135.220.15]:51670 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1950368AbcHROMp (ORCPT ); Thu, 18 Aug 2016 10:12:45 -0400 Date: Thu, 18 Aug 2016 16:12:42 +0200 From: Petr Mladek To: Chris Metcalf Cc: Peter Zijlstra , "Rafael J. Wysocki" , Russell King , Thomas Gleixner , Aaron Tomlin , Ingo Molnar , Andrew Morton , Daniel Thompson , "Ralf Baechle ralf @ linux-mips . org David S. Miller" , linux-mips@linux-mips.org, sparclinux@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace() methods Message-ID: <20160818141242.GK26194@pathway.suse.cz> References: <1471377024-2244-1-git-send-email-cmetcalf@mellanox.com> <1471377024-2244-2-git-send-email-cmetcalf@mellanox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1471377024-2244-2-git-send-email-cmetcalf@mellanox.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 2016-08-16 15:50:21, 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 the new "cpumask" method instead. > > The mips code ignored the "include_self" boolean but with this change > it will now also dump a local backtrace if requested. > > diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c > index 7429ad09fbe3..fea1fa7726e3 100644 > --- a/arch/mips/kernel/process.c > +++ b/arch/mips/kernel/process.c > @@ -569,9 +569,16 @@ static void arch_dump_stack(void *info) > dump_stack(); > } > > -void arch_trigger_all_cpu_backtrace(bool include_self) > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) > { > - smp_call_function(arch_dump_stack, NULL, 1); > + long this_cpu = get_cpu(); > + > + if (cpumask_test_cpu(this_cpu, mask) && !exclude_self) > + dump_stack(); The bit is not cleared in the mask. Therefore arch_dump_stack will get called for this CPU as well. We could either use similar tricks as in lib/nmi_backtrace(). I mean to copy the mask into a global variable and prevent parallel call with a backtrace_flag. Or we could ignore the exclude_self flag as it was done before. It is a separate problem after all and it need not be solved in this patch(set). > + > + smp_call_function_many(mask, arch_dump_stack, NULL, 1); > + > + put_cpu(); > } Otherwise the patch patch looks good to me. Best Regards, Petr