From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752610AbZHGEO7 (ORCPT ); Fri, 7 Aug 2009 00:14:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752273AbZHGEO6 (ORCPT ); Fri, 7 Aug 2009 00:14:58 -0400 Received: from mail-yw0-f177.google.com ([209.85.211.177]:65102 "EHLO mail-yw0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752132AbZHGEO5 (ORCPT ); Fri, 7 Aug 2009 00:14:57 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=KwFiFe2VqyX7vQj3LpHosWDl+d7BJz2A2PhK7DeIXsLtqEwD0IUvjSsBWfu6nhCkGJ WgjlZGRIy06q+HFRNEkydXXC/wKxeFDUgzyPbwhQTU5RNBbfNrngwZxOFSr06Z5froS5 JppYrkPkjEiDu/0o8P2C3rOd64/5BelHLG17Q= Subject: Re: [RFC][PATCH 4/5] tracing/filters: Provide basic regex support From: Tom Zanussi To: Frederic Weisbecker Cc: Li Zefan , Ingo Molnar , LKML , Steven Rostedt , Lai Jiangshan , Thomas Gleixner , Peter Zijlstra In-Reply-To: <20090806014941.GA24609@nowhere> References: <1249111408-8657-1-git-send-email-fweisbec@gmail.com> <1249111408-8657-5-git-send-email-fweisbec@gmail.com> <4A76782E.4030803@cn.fujitsu.com> <20090805224709.GH5025@nowhere> <4A7A2E73.7030403@cn.fujitsu.com> <20090806014941.GA24609@nowhere> Content-Type: text/plain Date: Thu, 06 Aug 2009 23:14:57 -0500 Message-Id: <1249618497.30024.36.camel@tropicana> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Frederic, On Thu, 2009-08-06 at 03:49 +0200, Frederic Weisbecker wrote: > On Thu, Aug 06, 2009 at 09:14:27AM +0800, Li Zefan wrote: > > Frederic Weisbecker wrote: > > > On Mon, Aug 03, 2009 at 01:39:58PM +0800, Li Zefan wrote: > > >> Frederic Weisbecker wrote: > > >>> This patch provides basic support for regular expressions in filters. > > >>> The common filter file doesn't support any regex but a new > > >>> filter_regex file is created for each subsystem/event. > > >>> > > >>> It supports the following types of regexp: > > >>> > > >>> - *match_beginning > > >>> - *match_middle* > > >>> - match_end* > > >>> - !don't match > > >>> > > >> I don't see why adding "filter_regex" is necessary, why not just make > > >> "filter" support regex? > > > > > > I did that because I feared about people beeing unable to filter using > > > * as a real character inside a filter string. > > > If we are using only one file, we are forced to get the '*' interpreted. > > > That would also break the ABI. > > > > > > > I think we don't maintain stable ABI for debugfs and we've been changing > > the "ABI" in debugfs/tracing/, but of course we shouldn't change it > > without good reasons. > > > Yeah. May be I'm too much careful there but i prefer not to take the risk. > > > > One alternative is to use '"' to prevent '*' to be translated, but seems > > using "filter_regex" is more convenient, so I agree with this patch. > > > The problem is that most of the time, the '"' is about mandatory to delimit > a string. > Say you want to filter the lock name &REISERFS_SB(sb)->lock, you can't do that > by just typing: > > echo name == &REISERFS_SB(sb)->lock > events/lockdep/filter > > because the '&' character is considered as an operator and that will trigger > an error. > Instead you must type: > > echo 'name == "&REISERFS_SB(sb)->lock"' > events/lockdep/filter > > The '' are there to delimit the string for echo, and the "" are interpreted > by the filter api which take it as a whole string and not strings interleaved > with operators. I even fear - and > may be considered as operators if we omit > the "". > > I also thought about using an antislash for those who don't want the * to > be interpreted. But although it seems intuitive, it's not as much as two > distinct and visible files. > > Also, we can think about the fact the regexp support could be extended one > day if someone needs to. And we could then encounter even more ambiguous > characters such as $, ^, [, {, etc... > This a nice new feature - I considered doing it (not complete regexp support, just * in strings) for the original patch, but ran out of time - glad you added it. I still think it makes sense to have some basic support for * in the regular filter file, so I'd vote for getting rid of the filter_regex file for now and just adding * support with the antislash escape to the regular filter file. If you later wanted to add more full-fledged regexp support and it didn't make sense to do it in the regular filter file, then you could go crazy and add the filter_regex later... Thanks, Tom