Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752135AbaKDXlK (ORCPT ); Tue, 4 Nov 2014 18:41:10 -0500 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.231]:24818 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751229AbaKDXlJ (ORCPT ); Tue, 4 Nov 2014 18:41:09 -0500 Date: Tue, 4 Nov 2014 18:41:02 -0500 From: Steven Rostedt To: Jiri Kosina Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Petr Mladek , "H. Peter Anvin" , Thomas Gleixner , "Paul E. McKenney" Subject: Re: [RFC][PATCH 12/12 v3] x86/nmi: Perform a safe NMI stack trace on all CPUs Message-ID: <20141104184102.4ecb3533@gandalf.local.home> In-Reply-To: References: <20141104155237.228431433@goodmis.org> <20141104160223.310714394@goodmis.org> X-Mailer: Claws Mail 3.10.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.130:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 5 Nov 2014 00:05:12 +0100 (CET) Jiri Kosina wrote: > On Tue, 4 Nov 2014, Steven Rostedt wrote: > > > From: "Steven Rostedt (Red Hat)" > > > > When trigger_all_cpu_backtrace() is called on x86, it will trigger an > > NMI on each CPU and call show_regs(). But this can lead to a hard lock > > up if the NMI comes in on another printk(). > > > > In order to avoid this, when the NMI triggers, it switches the printk > > routine for that CPU to call a NMI safe printk function that records the > > printk in a per_cpu seq_buf descriptor. After all NMIs have finished > > recording its data, the trace_seqs are printed in a safe context. Hmm, I need to update the change log to say seq_bufs instead of trace_seqs. > > > > Link: http://lkml.kernel.org/p/20140619213952.360076309@goodmis.org > > > > Acked-by: Paul E. McKenney > > Signed-off-by: Steven Rostedt > > I've been running the whole machinery that used to trigger very quickly > the complete hardlock of the machine (*) for the whole evening/night, and > it's still running flawlessly. > > Plus, as I said previously, I agree with the whole idea (given the > general nastiness of the problem and given the fact this simply has to be > fixed without pointless delays). > > I.e FWIW > > Tested-by: Jiri Kosina > Acked-by: Jiri Kosina > > for the whole series. Thanks! I'll update the commits. -- Steve > > (*) heavy printk() workload (**) + sysrq-l in parallel > (**) iptables logging every incoming packet + flood ping from another > machine > > Thanks, > -- 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/