linux-kernel - Re: [PATCH] perf stat: Do not show stats if workload fails

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Message-ID: <20131226142634.GF30980@ghostprotocols.net>
Date:	Thu, 26 Dec 2013 11:26:34 -0300
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	David Ahern <dsahern@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf stat: Do not show stats if workload fails

Em Thu, Dec 26, 2013 at 09:18:17AM -0500, David Ahern escreveu:
> On 12/26/13, 9:15 AM, Arnaldo Carvalho de Melo wrote:
> >Right, but I can't apply that patch, as it makes 'perf stat
> >whatever-workload' to fail, as I realized when doing a demo to someone
> >interested in using perf ;-\
> >
> >So for now I'm not applying that one.
> 
> right, so you want one with < 0 check or wait for something else? I
> was not expecting to find it in your perf/core branch, yet there it
> is.

I'll remove it from there, but try it, IIRC there will be some other
problem :-\

I'd have to reread the messages I sent, but from what I recall the
return from perf_evlist__start_workload() will _always_ be valid, i.e.
what you're testing there is just if the parent wrote a byte to a pipe
to signal the waiting child to call exec, and that _will_ work, the
exec()? perhaps not, you'd have to setup the signal error reporting
mechanism, etc.

Perhaps this should be somehow done by perf_evlist__start_workload, so
that what it reports is the result of the exec in the child, and not
merely if it managed to tell it to try to exec...

- Arnaldo

> >
> >Ah, at this point elves are everywhere, dammit! ;-)
> 
> An elf put it there?

Right, dwarves may be involved, didn't had the time to figure that
out...

> David
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