linux-kernel - Re: [RFC][PATCH 4/5] tracing/filters: Provide basic regex support

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Date:	Thu, 06 Aug 2009 09:14:27 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Tom Zanussi <tzanussi@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC][PATCH 4/5] tracing/filters: Provide basic regex support

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.

One alternative is to use '"' to prevent '*' to be translated, but seems
using "filter_regex" is more convenient, so I agree with this patch.

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