linux-kernel - Re: [PATCH 06/19] perf ftrace: Add support for --pid option

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Message-ID: <87fvvly1fd.fsf@sejong.aot.lge.com>
Date:	Thu, 11 Jul 2013 16:56:54 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Ahern <dsahern@...il.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 06/19] perf ftrace: Add support for --pid option

On Wed, 10 Jul 2013 16:18:20 +0200, Jiri Olsa wrote:
> On Wed, Jun 26, 2013 at 04:14:09PM +0900, Namhyung Kim wrote:
>> From: Namhyung Kim <namhyung.kim@....com>
>> 
>> The -p (--pid) option enables to trace existing process by its pid.
>
> hi,
> I can't get any output from -p for live subcommand:
>
> [jolsa@...va perf]$ pgrep yes
> 6443
> [jolsa@...va perf]$ sudo ./perf ftrace live -p `pgrep yes`

Hmm... looks like it's stuck on polling the trace_pipe:

  $ sudo strace ./perf ftrace -p `pgrep yes'
  ...
  poll([{fd=3, events=POLLIN}], 1, 4294967295


Need to investigate it more.

Along with it, I found that I didn't close fd in
__write_tracing_file().  I'll fix it in the next spin too.

Thanks for the review and testing!
Namhyung
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