linux-kernel - Re: [PATCH] perf sched latency: Fix removed thread issue

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Message-ID: <20151103074148.GC23878@krava.brq.redhat.com>
Date:	Tue, 3 Nov 2015 08:41:48 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Jiri Olsa <jolsa@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mohit Agrawal <moagrawa@...hat.com>
Subject: Re: [PATCH] perf sched latency: Fix removed thread issue

On Mon, Nov 02, 2015 at 07:53:53PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Mon, Nov 02, 2015 at 12:10:25PM +0100, Jiri Olsa escreveu:
> > If machine's thread gets excited (EXIT event is received),
> > we set thread->dead = true and it is later on removed from
> > machine's tree if the pid is reused on new thread.
> 
> > The latency subcommand holds tree of working atoms sorted
> > by thread's pid/tid. If there's new thread with same pid
> 
> Humm, wher is the latency subcommand handling the EXIT event?
> 
> I see:
> 
>    perf_sched__lat
>      perf_sched__read_events
>        session = perf_session__new(&file, false, &sched->tool);
>        perf_session__process_events(session)
> 
> And sched->tool->exit() is not set, which will make
> perf_session__process_events(), when calling perf_tool__fill_defaults()
> set it to process_event_stub() which will do nothing for
> PERF_RECORD_EXIT events, no?

yep, latency command does not handle EXIT event, but the
thread is removed via FORK event.. the first changelog
paragraph might be a little misleading sorry ;-)

could you please change it to:

---
If machine's thread gets excited (EXIT event is received),
we set thread->dead = true and it is later on removed from
machine's tree if the pid is reused on new thread.

We dont handle EXIT command in 'perf sched latency',
however the old thread is removed anyway when FORK
event is received for new thrad with same pid/tid.
---

thanks,
jirka
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