From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754926Ab0CQTP0 (ORCPT ); Wed, 17 Mar 2010 15:15:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59589 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753361Ab0CQTPZ (ORCPT ); Wed, 17 Mar 2010 15:15:25 -0400 Message-ID: <4BA12A23.4030109@redhat.com> Date: Wed, 17 Mar 2010 15:14:43 -0400 From: Masami Hiramatsu User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.8) Gecko/20100301 Fedora/3.0.3-1.fc11 Thunderbird/3.0.3 MIME-Version: 1.0 To: Mark Wielaard CC: Ingo Molnar , lkml , systemtap , DLE , Frederic Weisbecker , Arnaldo Carvalho de Melo , Paul Mackerras , Mike Galbraith , Peter Zijlstra Subject: Re: [PATCH -tip 10/10] perf probe: Accessing members in data structures References: <20100316220515.32050.82185.stgit@localhost6.localdomain6> <20100316220626.32050.57552.stgit@localhost6.localdomain6> <1268821537.6022.12.camel@springer.wildebeest.org> In-Reply-To: <1268821537.6022.12.camel@springer.wildebeest.org> X-Enigmail-Version: 1.0.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mark Wielaard wrote: > On Tue, 2010-03-16 at 18:06 -0400, Masami Hiramatsu wrote: >> Support accessing members in the data structures. With this, >> perf-probe accepts data-structure members(IOW, it now accepts >> dot '.' and arrow '->' operators) as probe arguemnts. >> >> e.g. >> >> ./perf probe --add 'schedule:44 rq->curr' >> >> ./perf probe --add 'vfs_read file->f_op->read file->f_path.dentry' >> >> Note that '>' can be interpreted as redirection in command-line. > > If you find that a problem then you can do like SystemTap does and allow > '.' in place of '->'. In the code you already use the > perf_probe_arg_field ref flag only to check that the DIE gives you the > same information. So you could just drop that and use any separator. > Then you decide based on whether you see a DW_TAG_pointer_type. This > gives the user some extra flexibility by letting them not having to care > about specifying extra type information already available elsewhere. Thanks, when designing this feature, I considered it too. Since perf probe already support displaying source code by --line option, users will read the probed code itself and try to probe it. In that case, I think they naturally use '.' and '->' as they read (they might try to copy & paste it). So, I think that it would be good to support both of '.' and '->' as they are used in the code, because it will not confuse users. Thank you, -- Masami Hiramatsu e-mail: mhiramat@redhat.com