Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965879AbaFSXDd (ORCPT ); Thu, 19 Jun 2014 19:03:33 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46673 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964958AbaFSXDc (ORCPT ); Thu, 19 Jun 2014 19:03:32 -0400 Date: Fri, 20 Jun 2014 01:03:28 +0200 (CEST) From: Jiri Kosina To: Steven Rostedt cc: linux-kernel@vger.kernel.org, Linus Torvalds , Ingo Molnar , Andrew Morton , Michal Hocko , Jan Kara , Frederic Weisbecker , Dave Anderson , Petr Mladek Subject: Re: [RFC][PATCH 0/3] x86/nmi: Print all cpu stacks from NMI safely In-Reply-To: <20140619185810.4137e14b@gandalf.local.home> Message-ID: References: <20140619213329.478113470@goodmis.org> <20140619185810.4137e14b@gandalf.local.home> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 19 Jun 2014, Steven Rostedt wrote: > > The idea basically is to *switch* what arch_trigger_all_cpu_backtrace() > > and arch_trigger_all_cpu_backtrace_handler() are doing; i.e. use the NMI > > as a way to stop all the CPUs (one by one), and let the CPU that is > > sending the NMIs around to actually walk and dump the stacks of the CPUs > > receiving the NMI IPI. > > And this is cleaner? Stopping a CPU via NMI and then what happens if > something else goes wrong and that CPU never starts back up? This > sounds like something that can cause more problems than it was > reporting on. It's going to get NMI in exactly the same situations it does with the current arch_trigger_all_cpu_backtrace(), the only difference being that it doesn't try to invoke printk() from inside NMI. The IPI-NMI is used solely as a point of synchronization for the stack dumping. > Then you also need to print out the data while the NMIs still spin. Exactly, that's actually the whole point. Thanks, -- Jiri Kosina SUSE Labs -- 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/