Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753128AbZIHAwR (ORCPT ); Mon, 7 Sep 2009 20:52:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752911AbZIHAwQ (ORCPT ); Mon, 7 Sep 2009 20:52:16 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:59297 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752872AbZIHAwQ (ORCPT ); Mon, 7 Sep 2009 20:52:16 -0400 Message-ID: <4AA5AA0F.4060104@cn.fujitsu.com> Date: Tue, 08 Sep 2009 08:49:19 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1b3pre) Gecko/20090513 Fedora/3.0-2.3.beta2.fc11 Thunderbird/3.0b2 MIME-Version: 1.0 To: Peter Zijlstra CC: Ingo Molnar , Steven Rostedt , Frederic Weisbecker , Tom Zanussi , Jason Baron , LKML Subject: Re: [PATCH 4/6] perf_counter: Add PERF_COUNTER_IOC_SET_FILTER ioctl References: <4AA4C04D.1050201@cn.fujitsu.com> <4AA4C0B3.3070300@cn.fujitsu.com> <1252341871.7959.37.camel@laptop> <20090907164852.GA6485@elte.hu> <1252342545.7959.42.camel@laptop> In-Reply-To: <1252342545.7959.42.camel@laptop> 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 Content-Length: 1650 Lines: 40 Peter Zijlstra wrote: > On Mon, 2009-09-07 at 18:48 +0200, Ingo Molnar wrote: >> * Peter Zijlstra wrote: >> >>> On Mon, 2009-09-07 at 16:13 +0800, Li Zefan wrote: >>>> Allow to set profile filter via ioctl. >>> Hrm,.. not at all sure about this.. what are the ABI implications? >> I think the ABI should be fine if it's always a sub-set of C syntax. >> That would be C expressions initially. Hm? > > Right, so I've no clue what filter expressions look like, and the > changelog doesn't help us at all. It doesn't mention its a well > considered decision to henceforth freeze the expression syntax. > > Of course, since filters so far only work with tracepoint things, and > since you can only come by tracepoint things through debugfs, and since > anything debugfs is basically a free-for-all ABI-less world, we might be > good, but then this is a very ill-defined ioctl() indeed. > > So please, consider this well -- there might not be a second chance. > Ok, the expressions are: 1. S = opr1 op opr2 (op: ==, !=, <, <=, >, >=. opr1 should be a field in the format file) 2. E = S1 op S2 (op: ||, &&) 3. E = E1 op E2 (op: ||, &&) 4. () can be used I don't the syntax will be changed, but we may extend it, like adding not ! operator. Like, for a func ptr, besides "func==0xccee4400", we may want to allow "func==foo". Those extentions are ok for the ABI, right? -- 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/