linux-kernel - Re: [PATCH] perf record: Fix poll return value propagation

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Date:	Tue, 03 Jun 2014 12:21:43 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Jiri Olsa <jolsa@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] perf record: Fix poll return value propagation

On Mon,  2 Jun 2014 20:02:06 +0200, Jiri Olsa wrote:
> If the perf record command is interrupted in record__mmap_read_all
> function, the 'done' is set and err has the latest poll return
> value, which is most likely positive number (= number of pollfds
> ready to read).
>
> This 'positive err' is then propagated to the exit code, resulting
> in not finishing the perf.data header properly, causing following
> error in report:
>
>   # perf record -F 50000 -a
>
>   ---
>   make the system real busy, so there's more chance
>   to interrupt perf in event writing code
>   ---
>
>   ^C[ perf record: Woken up 16 times to write data ]
>   [ perf record: Captured and wrote 30.292 MB perf.data (~1323468 samples) ]
>
>   # perf report --stdio > /dev/null
>   WARNING: The perf.data file's data size field is 0 which is unexpected.
>   Was the 'perf record' command properly terminated?
>
> Fixing this by checking for positive poll return value
> and setting err to 0.

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung
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