From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967737AbcA1P4G (ORCPT ); Thu, 28 Jan 2016 10:56:06 -0500 Received: from smtprelay0167.hostedemail.com ([216.40.44.167]:34047 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965872AbcA1P4D (ORCPT ); Thu, 28 Jan 2016 10:56:03 -0500 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1539:1593:1594:1711:1730:1747:1777:1792:2393:2553:2559:2562:3138:3139:3140:3141:3142:3352:3622:3865:3867:3868:3871:3872:4250:4470:5007:6261:7875:7903:9707:10004:10400:10848:10967:11232:11658:11914:12517:12519:12740:13069:13311:13357:14659:21080:30054:30070:30090:30091,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0,LFtime:2,LUA_SUMMARY:none X-HE-Tag: step91_51486344ca61e X-Filterd-Recvd-Size: 2037 Date: Thu, 28 Jan 2016 10:55:57 -0500 From: Steven Rostedt To: Peter Zijlstra Cc: Mathieu Desnoyers , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, "Paul E. McKenney" Subject: Re: [RFC][BUG] tracer: Fails to work Message-ID: <20160128105557.2971f8b9@gandalf.local.home> In-Reply-To: <20160128152957.GU6356@twins.programming.kicks-ass.net> References: <20160128080859.GB6357@twins.programming.kicks-ass.net> <1069612139.6639.1453988280286.JavaMail.zimbra@efficios.com> <20160128135733.GQ6356@twins.programming.kicks-ass.net> <1616014588.6697.1453991896740.JavaMail.zimbra@efficios.com> <20160128144705.GS6356@twins.programming.kicks-ass.net> <1504204180.6731.1453992833257.JavaMail.zimbra@efficios.com> <20160128152957.GU6356@twins.programming.kicks-ass.net> X-Mailer: Claws Mail 3.13.1 (GTK+ 2.24.29; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 28 Jan 2016 16:29:57 +0100 Peter Zijlstra wrote: > On Thu, Jan 28, 2016 at 02:53:53PM +0000, Mathieu Desnoyers wrote: > > On x86, many BIOS wipe the memory content even after a warm reset :( > > The most reliable solution I found on x86 is to use kexec() to > > boot into a new kernel, mount the DAX filesystem again and read the > > buffers from there. > > kexec() is tricky when the kernel is still prefectly fine, I doubt it'll > work when I've hosed it properly :/ I use it all the time when a kernel crashes. Well, kexec and kdump. Which by the way, the crash utility has a way to read the ftrace ring buffer from a kexec kdump core file. -- Steve