From patchwork Thu Jul 14 20:50:30 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Metcalf X-Patchwork-Id: 9230651 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 2F3C260574 for ; Thu, 14 Jul 2016 20:53:00 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 20DDC2817F for ; Thu, 14 Jul 2016 20:53:00 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 158C32830A; Thu, 14 Jul 2016 20:53:00 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 9BD5B2817F for ; Thu, 14 Jul 2016 20:52:59 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1bNnbm-0001Jf-4s; Thu, 14 Jul 2016 20:51:46 +0000 Received: from mail-il-dmz.mellanox.com ([193.47.165.129] helo=mellanox.co.il) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1bNnbf-00012b-83 for linux-arm-kernel@lists.infradead.org; Thu, 14 Jul 2016 20:51:42 +0000 Received: from Internal Mail-Server by MTLPINE1 (envelope-from cmetcalf@mellanox.com) with ESMTPS (AES256-SHA encrypted); 14 Jul 2016 23:50:39 +0300 Received: from ld-1.internal.tilera.com (ld-1.internal.tilera.com [10.15.7.41]) by mtbu-labmail01.internal.tilera.com (8.14.4/8.14.4) with ESMTP id u6EKobjG015918; Thu, 14 Jul 2016 16:50:37 -0400 Received: (from cmetcalf@localhost) by ld-1.internal.tilera.com (8.14.4/8.14.4/Submit) id u6EKobxO028080; Thu, 14 Jul 2016 16:50:37 -0400 From: Chris Metcalf To: Peter Zijlstra , "Rafael J. Wysocki" , Petr Mladek , Russell King , Thomas Gleixner , Aaron Tomlin , Ingo Molnar , Andrew Morton , Daniel Thompson , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 2/4] nmi_backtrace: do a local dump_stack() instead of a self-NMI Date: Thu, 14 Jul 2016 16:50:30 -0400 Message-Id: <1468529432-28026-3-git-send-email-cmetcalf@mellanox.com> X-Mailer: git-send-email 2.7.2 In-Reply-To: <1468529432-28026-1-git-send-email-cmetcalf@mellanox.com> References: <1468529432-28026-1-git-send-email-cmetcalf@mellanox.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160714_135139_997329_9C3E3244 X-CRM114-Status: GOOD ( 13.30 ) 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: Chris Metcalf MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Currently on arm there is code that checks whether it should call dump_stack() explicitly, to avoid trying to raise an NMI when the current context is not preemptible by the backtrace IPI. Similarly, the forthcoming arch/tile support uses an IPI mechanism that does not support generating an NMI to self. Accordingly, move the code that guards this case into the generic mechanism, and invoke it unconditionally whenever we want a backtrace of the current cpu. It seems plausible that in all cases, dump_stack() will generate better information than generating a stack from the NMI handler. The register state will be missing, but that state is likely not particularly helpful in any case. Or, if we think it is helpful, we should be capturing and emitting the current register state in all cases when regs == NULL is passed to nmi_cpu_backtrace(). Signed-off-by: Chris Metcalf Acked-by: Aaron Tomlin --- arch/arm/kernel/smp.c | 9 --------- lib/nmi_backtrace.c | 10 ++++++++++ 2 files changed, 10 insertions(+), 9 deletions(-) diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index a3f422022561..0b710ca893aa 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -748,15 +748,6 @@ core_initcall(register_cpufreq_notifier); static void raise_nmi(cpumask_t *mask) { - /* - * Generate the backtrace directly if we are running in a calling - * context that is not preemptible by the backtrace IPI. Note - * that nmi_cpu_backtrace() automatically removes the current cpu - * from mask. - */ - if (cpumask_test_cpu(smp_processor_id(), mask) && irqs_disabled()) - nmi_cpu_backtrace(NULL); - smp_cross_call(mask, IPI_CPU_BACKTRACE); } diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c index 276540f6407e..c990e21acc5a 100644 --- a/lib/nmi_backtrace.c +++ b/lib/nmi_backtrace.c @@ -45,6 +45,16 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, } cpumask_copy(to_cpumask(backtrace_mask), mask); + + /* + * Don't try to send an NMI to this cpu; it may work on some + * architectures, but on others it may not, and we'll get + * information at least as useful just by doing a dump_stack() here. + * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit. + */ + if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask))) + nmi_cpu_backtrace(NULL); + if (!cpumask_empty(to_cpumask(backtrace_mask))) { pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n", this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));