linux-kernel - Re: [PATCH] perf-probe: make "perf-probe -L <function>" display the absolute path and absolute line number

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Message-ID: <4D30267B.9080406@hitachi.com>
Date:	Fri, 14 Jan 2011 19:33:31 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Franck Bui-Huu <vagabon.xyz@...il.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	lkml <linux-kernel@...r.kernel.org>,
	2nddept-manager@....hitachi.co.jp
Subject: Re: [PATCH] perf-probe: make "perf-probe -L <function>" display the
 absolute path and absolute line number

Hi Franck,

(2011/01/14 18:03), Franck Bui-Huu wrote:
> But if you think it should be used to hint for a probe point syntax,
> (you'll probably use copy & paste since it uses absolute path name),

Not only for copy&paste, but also for avoiding confusion.
Please imagine that user see this output.

   </usr/src/debug/kernel-2.6.35.fc14/linux-2.6.35.x86_64/kernel/sched.c:3823>
        10         rq = cpu_rq(cpu);
        11         rcu_note_context_switch(cpu);

"Why the definition line number and starting line number are different?"
"How I can put a probe?  sched.c:3823 ... + 10??"
"Or, it's just buggy! report it!"

I don't want this.

> then this patch is wrong.

Yeah, but just a _bit_. Basically, I agree with your idea of showing
actual path of the function, because, indeed, perf-probe just shows
the first one even if there are many same-name functions.

So, here, I had suggested an enhancement idea;

  $ perf probe -L schedule:0-1
  <schedule@...r/src/debug/kernel-2.6.35.fc14/linux-2.6.35.x86_64/kernel/sched.c:0>
        0  asmlinkage void __sched schedule(void)
        1  {

This is acceptable, because it shows which function you see and
it also gives you how you can specify a probe point on a function
line.

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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