linux-kernel - Re: [PATCH 04/10] perf record: Filter out POLLHUP'ed file descriptors

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Message-ID: <54085BC8.40403@intel.com>
Date:	Thu, 04 Sep 2014 15:32:08 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>
CC:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	David Ahern <dsahern@...il.com>,
	Don Zickus <dzickus@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 04/10] perf record: Filter out POLLHUP'ed file descriptors

On 09/04/2014 12:59 AM, Arnaldo Carvalho de Melo wrote:
> From: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> So that we don't continue polling on vanished file descriptors, i.e.
> file descriptors for events monitoring threads that exited.
> 
> I.e. the following 'perf record' command now exits as expected, instead
> of staying in an eternal loop:
> 
>   $ sleep 5s &
>   $ perf record -p `pidof sleep`
> 
> Reported-by: Jiri Olsa <jolsa@...hat.com>
> Acked-by: Jiri Olsa <jolsa@...nel.org>
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: David Ahern <dsahern@...il.com>
> Cc: Don Zickus <dzickus@...hat.com>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Mike Galbraith <efault@....de>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Stephane Eranian <eranian@...gle.com>
> Link: http://lkml.kernel.org/n/tip-ftg46awsyfjc3axb0xm63oig@git.kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>  tools/perf/builtin-record.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 87e28a4e33ba..b87708ce09c9 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -467,6 +467,9 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>  			if (err > 0 || (err < 0 && errno == EINTR))
>  				err = 0;
>  			waking++;
> +
> +			if (perf_evlist__filter_pollfd(rec->evlist, POLLERR | POLLHUP) == 0)

If the poll fds only include the ones mmapped, then mightn't it filter out
ones still in use? e.g. what if you record two processes and one exits?

> +				done = 1;
>  		}
>  
>  		/*
> 

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