linux-kernel - Re: [tip:perf/core] perf probe: Clean up probe_point_lazy

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Message-ID: <4D809311.5050806@hitachi.com>
Date:	Wed, 16 Mar 2011 19:38:09 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...hat.com, hpa@...or.com, acme@...hat.com,
	linux-kernel@...r.kernel.org, fweisbec@...il.com,
	tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org,
	"2nddept-manager@....hitachi.co.jp" 
	<2nddept-manager@....hitachi.co.jp>
Subject: Re: [tip:perf/core] perf probe: Clean up probe_point_lazy_walker()
 return value

(2011/03/16 16:59), Peter Zijlstra wrote:
> On Tue, 2011-03-15 at 23:18 +0000, tip-bot for Ingo Molnar wrote:
> 
>> perf probe: Clean up probe_point_lazy_walker() return value
> 
>> --- a/tools/perf/util/probe-finder.c
>> +++ b/tools/perf/util/probe-finder.c
>> @@ -1328,7 +1328,7 @@ static int probe_point_lazy_walker(const char *fname, int lineno,
>>  	 * Continue if no error, because the lazy pattern will match
>>  	 * to other lines
>>  	 */
>> -	return ret < 0 ?: 0;
>> +	return ret < 0 ? ret : 0;
>>  }
> 
> It is a slight change in semantics though, the return value will now be
> negative instead of 1. If its used as a boolean that's fine, but still.
> 
> I'd have changed it to:
> 
>   return ret < 0;
> 
> Which is identical to the previous statement.

Sorry this was my mistake, that statement actually aims to
what Ingo has done.

If probe_point_lazy_walker() returns non-zero value,
die_walk_lines() returns immediately, because a positive return
value means the handler finds line and wanna stop walking on
the lines, and a negative return value means some errors
occurred in the handler and must stop.

However, probe_point_lazy_walker() has to continue to walk,
because given lazy-pattern can match several lines. Thus, this
must return 0 if ret is a positive value, and return an error code
if ret is a negative value.

Thank you,


-- 
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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