linux-kernel - Re: Re: [PATCH v2 1/5] perf probe: Split add_perf_probe

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Message-ID: <20150911162934.GE3447@danjae.kornet>
Date:	Sat, 12 Sep 2015 01:29:34 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>
Cc:	"Wangnan (F)" <wangnan0@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"pi3orama@....com" <pi3orama@....com>
Subject: Re: Re: [PATCH v2 1/5] perf probe: Split add_perf_probe_events()

On Thu, Sep 10, 2015 at 08:10:16AM +0000, 平松雅巳 / HIRAMATU，MASAMI wrote:
> Hi Namhyung,
> 
> From: Namhyung Kim [mailto:namhyung@...il.com] On Behalf Of Namhyung Kim
> >
> >Hi Masami,
> >
> >On Thu, Sep 10, 2015 at 05:00:07AM +0000, 平松雅巳 / HIRAMATU，MASAMI wrote:
> >> >From: Namhyung Kim [mailto:namhyung@...il.com] On Behalf Of Namhyung Kim
> >> >The del_perf_probe_events() uses strfilter, but I think it can be
> >> >problematic if other instances or users are using similar events at
> >> >the same time.
> >>
> >> Yeah, since perf probe doesn't lock the ftrace, there should be a
> >> timing bug, but it can be fixed easily by ignoring -ENOENT. :)
> >
> >By ignoring -ENOENT?  Are you saying that there's a race between two
> >deleters?  Yes, of course, but I think that the bug will hit an adder
> >and a deleter especially if automatic probing is used (by eBPF and/or
> >SDT recording).
> 
> So, I don't think we need the automatic event removing. Instead, I'd like to
> suggest to keep it on the list.

But why?  Do you want reuse the probes for next record session?

I think if something is generated automatically, it should be removed
automatically..

Thanks,
Namhyung
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