Date: Wed, 14 Dec 2016 18:59:11 +0100
From: Jiri Olsa <jolsa@redhat.com>
To: kan.liang@intel.com
Cc: acme@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com,
        peterz@infradead.org, jolsa@kernel.org, adrian.hunter@intel.com,
        andi@firstfloor.org
Subject: Re: [PATCH] perf tools: ignore zombie process for user profile
Message-ID: <20161214175911.GA14085@krava>
References: <1481737685-24595-1-git-send-email-kan.liang@intel.com>
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On Wed, Dec 14, 2016 at 12:48:05PM -0500, kan.liang@intel.com wrote:
> From: Kan Liang <kan.liang@intel.com>
> 
> If user has zombie process, the perf record -u will error out.
> Here is an example.
>  $ ./testd &
>  [1] 23796
>  $ sudo perf record -e cycles -u kan
>  Error:
>  The sys_perf_event_open() syscall returned with 3 (No such process) for
>  event (cycles).
>  /bin/dmesg may provide additional information.
>  No CONFIG_PERF_EVENTS=y kernel support configured?
> 
> The source code of testd is as below.
>  int main() {
> 
> 	if (fork())
> 	{
> 		while (1);
> 	}
> 	return 0;
>  }
> 
> Zombie process is dead process. It is meaningless to profile it.
> It's better to ignore it for user profile.

I recently posted different patch for same issue:
  http://marc.info/?l=linux-kernel&m=148153895827359&w=2

jirka