linux-kernel - Re: [PATCH] tracing: Add a way to filter function addresses to function names

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Message-ID: <ed4ea9ae-78bf-b323-9380-47b1fd58c72b@huawei.com>
Date:   Tue, 20 Dec 2022 09:40:05 +0800
From:   Zheng Yejian <zhengyejian1@...wei.com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ross Zwisler <zwisler@...gle.com>,
        Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH] tracing: Add a way to filter function addresses to
 function names


On 2022/12/20 02:21, Steven Rostedt wrote:
> On Mon, 19 Dec 2022 10:38:50 +0800
> Zheng Yejian <zhengyejian1@...wei.com> wrote:
> 
>>> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
>>> index 33e0b4f8ebe6..db6e2f399440 100644
>>> --- a/kernel/trace/trace_events.c
>>> +++ b/kernel/trace/trace_events.c
>>> @@ -2822,7 +2822,7 @@ static __init int setup_trace_triggers(char *str)
>>>    		if (!trigger)
>>>    			break;
>>>    		bootup_triggers[i].event = strsep(&trigger, ".");
>>> -		bootup_triggers[i].trigger = strsep(&trigger, ".");
>>> +		bootup_triggers[i].trigger = strsep(&trigger, "");
>>
>> Would it be better to change to:
>>
>>        bootup_triggers[i].trigger = trigger;
>>
> 
> Sure, I'll make the update.
> 
>> Because there is unnecessary loop if call strsep(s, "") :-)
>>     strsep(s, ct) {
>>       strpbrk(cs, ct) {
>>         // when 'ct' is empty string, here will always return NULL
>>         // after traversing string 'cs'
> 
> I'm not sure what you mean about an extra loop.

I just mean above "traversing string 'cs'" in strpbrk(s, "") is 
unnecessary. Sorry for making the ambiguity :-(

> 
> Thanks,
> 
> -- Steve
>