linux-kernel - Re: A Bug Inquiry in linux/tools/perf/builtin-record.c

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Message-ID: <87lhwyuwpy.fsf@sejong.aot.lge.com>
Date:	Wed, 26 Feb 2014 17:03:37 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	xiakaixu <xiakaixu@...wei.com>
Cc:	<a.p.zijlstra@...llo.nl>, <paulus@...ba.org>, <mingo@...hat.com>,
	<acme@...stprotocols.net>, <linux-kernel@...r.kernel.org>,
	Huxinwei <huxinwei@...wei.com>, Genghui <hui.geng@...wei.com>,
	<peifeiyue@...wei.com>
Subject: Re: A Bug Inquiry in linux/tools/perf/builtin-record.c

Hi xiakaixu,

> 于 2014/2/19 9:48, xiakaixu 写道:
>> Hi all,
>> 
>> There is a bug found in my work when running "perf record". The basic information
>> is here. As we know, perf record is a parent process and the programme traced is
>> a child process when running "perf record". Sometimes the child process become
>> zombie state and disappear until the parent process is killed. The bug stays in linux/
>> tools/perf/builtin-record.c.
>> *********************************************************************
>> static int __cmd_record(struct perf_record *rec, int argc, const char **argv)
>>     ......
>> 	if (hits == rec->samples) {
>>                          if (done)
>>                                  break;
>>                          err = poll(evsel_list->pollfd, evsel_list->nr_fds, -1);
>>                          waking++;
>>                  }
>>     ......
>> *********************************************************************
>> The parent process still call the function
>> poll(evsel_list->pollfd, evsel_list->nr_fds, -1) when the child process has exited
>> already, which caused a zombie process.
>> 
>> May I have your opinion ?
>> Waiting for your reply!

Do you have a real bug report based on this?

AFAIK perf record installed a signal handler for SIGCHLD so it'll set
the 'done' variable when child exits and then break the loop.

Thanks,
Namhyung
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