From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751330AbZH0R3Z (ORCPT ); Thu, 27 Aug 2009 13:29:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751267AbZH0R3Y (ORCPT ); Thu, 27 Aug 2009 13:29:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20174 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751230AbZH0R3X (ORCPT ); Thu, 27 Aug 2009 13:29:23 -0400 Message-ID: <4A96C345.3060505@redhat.com> Date: Thu, 27 Aug 2009 13:32:53 -0400 From: Masami Hiramatsu User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Thunderbird/3.0b3 MIME-Version: 1.0 To: Frederic Weisbecker CC: Ingo Molnar , LKML , Steven Rostedt Subject: Re: [GIT PULL] tracing/kprobes: Add dynamic tracepoints + instruction decoder References: <1251340337-5640-1-git-send-email-fweisbec@gmail.com> <4A969F96.2020107@redhat.com> <20090827152539.GE6058@nowhere> In-Reply-To: <20090827152539.GE6058@nowhere> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Frederic Weisbecker wrote: > On Thu, Aug 27, 2009 at 11:00:38AM -0400, Masami Hiramatsu wrote: >> Frederic Weisbecker wrote: >>> Ingo, >>> >>> This is the kprobes tracing pile of patches. I've tested it >>> successfully by setting some kprobes through debugfs by hand. >>> >>> It brings no known regressions. >>> >>> However, the stress test provided by Masami have revealed some >>> unstable points. Some symbols are unsafe to probe and raise >>> probing recursion. >>> >>> I've added a tiny patch in the series that helps identifying the >>> kprobe that has raised such situation. >>> For example it has learned me today that it's unsafe to trace >>> ret_from_exception() (obviously: it's on the int 3 handler path). >> >> Thank you, Frederic. >> >> I'm currently fixing those problems on x86-64 (on kvm). >> I'll also check it on x86-32, and fix it. >> >> Thanks > > > > Cool. > Don't hesitate to interate through small patches that fix these > sites. > > So that I can continue to test it over time and report you what I find, > may be I can try to fix some of them too. > > I haven't fixed ret_from_exception because I wasn't sure about the > right thing to do: putting it in the kprobes section or blacklist its > name. It's a bit more delicate to put assembly code into sections so... :) It depends on implementation, but I think blacklist is the last resort. :) AFAIK, some assembly codes are already pushed into kprobes section. Thank you, -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division e-mail: mhiramat@redhat.com