linux-kernel - Re: [PATCH] perf stat: Fix default logfd to use stderr

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Date:	Tue, 19 Jun 2012 13:31:58 +0200
From:	Robert Richter <robert.richter@....com>
To:	Stephane Eranian <eranian@...gle.com>
CC:	Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jim Cromie <jim.cromie@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	<stable@...r.kernel.org>
Subject: Re: [PATCH] perf stat: Fix default logfd to use stderr

On 19.06.12 08:09:31, Stephane Eranian wrote:
> On Tue, Jun 19, 2012 at 4:13 AM, Namhyung Kim <namhyung@...nel.org> wrote:
> > Hi, Robert
> >
> > On Mon, 18 Jun 2012 16:51:08 +0200, Robert Richter wrote:
> >> On 29.09.11 18:48:01, Arnaldo Carvalho de Melo wrote:
> >>> From: Jim Cromie <jim.cromie@...il.com>
> >>>
> >>> This perf stat option emulates valgrind's --log-fd option, allowing the
> >>> user to send perf results elsewhere, and leaving stderr for use by the
> >>> program under test.  This complements --output file option, and is
> >>> mutually exclusive with it.
> >>>
> >>>    3>results  perf stat --log-fd 3          -- $cmd
> >>>    3>>results perf stat --log-fd 3 --append -- $cmd
> >>>
> >>> The perl distro's make test.valgrind target uses valgrind's --log-fd
> >>> option, I've adapted it to invoke perf also, and tested this patch
> >>> there.
> >>>
> >>> Link: http://lkml.kernel.org/r/1315437244-3788-2-git-send-email-jim.cromie@gmail.com
> >>> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> >>> Signed-off-by: Jim Cromie <jim.cromie@...il.com>
> >>> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> >>
> >> With certain shell redirections this (56f3bae) fails with a log fd
> >> setup failure. Fix below.
> >>
> >
> > It looks somewhat related to Stephane's patch. Can you we check it too?
> >
> > http://lkml.indiana.edu/hypermail/linux/kernel/1205.1/04232.html

I applied the patch to my tree and this works too. Both patches
basically avoid fdopen() if a log-fd option is not given.

After reviewing the code again I noticed my code breaks the -o option.
So Stephane's patch is fine for me too, except for the fact that
--log-fd 0 is ignored. Maybe we change this by initializing output_fd
with -1 and modify the checks of output_fd?

> Yes, my patch is needed and it was posted over a month ago now.....
> Arnaldo, please apply my patch.

It is in the pull request for Ingo.

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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