From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754623Ab2APMx5 (ORCPT ); Mon, 16 Jan 2012 07:53:57 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:41246 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750827Ab2APMx4 (ORCPT ); Mon, 16 Jan 2012 07:53:56 -0500 Date: Mon, 16 Jan 2012 13:53:30 +0100 From: Ingo Molnar To: Steven Rostedt Cc: Oleg Nesterov , Linus Torvalds , Ingo Molnar , Masami Hiramatsu , Seiji Aguchi , linux-kernel@vger.kernel.org, Masami Hiramatsu Subject: Re: [GIT PULL] tracing: make signal tracepoints more useful Message-ID: <20120116125329.GB31667@elte.hu> References: <20120110174509.GA30802@redhat.com> <20120113182015.GA3902@redhat.com> <20120115182441.GA24694@redhat.com> <20120116074540.GE15641@elte.hu> <1326717070.7642.144.camel@gandalf.stny.rr.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1326717070.7642.144.camel@gandalf.stny.rr.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=AWL,BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] 0.0 AWL AWL: From: address is in the auto white-list Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Steven Rostedt wrote: > On Mon, 2012-01-16 at 08:45 +0100, Ingo Molnar wrote: > > > Looks good to me at a first (quick) sight, except this bit > > which changes the ABI: > > > > > > - TP_printk("sig=%d errno=%d code=%d comm=%s pid=%d", > > > > + TP_printk("sig=%d errno=%d code=%d comm=%s pid=%d grp=%d res=%d", > > > > That's not how we change tracepoints generally - we add a new > > one and eventually phase out the old one. Which apps/tools rely > > on the old tracepoint? If it's exactly zero apps then we might > > be able to change it, but this needs to be investigated. > > But this tracepoint wasn't changed, it was added on to. > There's a difference. Any tool that uses this (including > something like powertop) should be able to handle it. [...] That's mostly true in theory - the question is, is it true in practice? Say if an app relies on the smaller data structure, it sure might get surprised by the kernel writing a wider record ... Thanks, Ingo