Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030512AbcCQWil (ORCPT ); Thu, 17 Mar 2016 18:38:41 -0400 Received: from casper.infradead.org ([85.118.1.10]:46357 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754674AbcCQWic (ORCPT ); Thu, 17 Mar 2016 18:38:32 -0400 Date: Thu, 17 Mar 2016 23:38:21 +0100 From: Peter Zijlstra To: Chris Metcalf Cc: Russell King , Thomas Gleixner , Aaron Tomlin , Ingo Molnar , Andrew Morton , Daniel Thompson , x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Paul McKenney Subject: Re: [PATCH v2 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace() methods Message-ID: <20160317223821.GZ6344@twins.programming.kicks-ass.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56EB3050.3060607@mellanox.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1324 Lines: 25 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.