linux-kernel - Re: [PATCH -tip perf/probes 00/10] x86 insn decoder bugfixes and perf-probe syntax changes

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Message-ID: <4AF04717.3020008@redhat.com>
Date:	Tue, 03 Nov 2009 10:07:03 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frédéric Weisbecker 
	<fweisbec@...il.com>, lkml <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jim Keniston <jkenisto@...ibm.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Jason Baron <jbaron@...hat.com>,
	"K.Prasad" <prasad@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>
Subject: Re: [PATCH -tip perf/probes 00/10] x86 insn decoder bugfixes and
 perf-probe syntax changes

Ingo Molnar wrote:
> * Masami Hiramatsu<mhiramat@...hat.com>  wrote:
>> Masami Hiramatsu wrote:
>>> Masami Hiramatsu wrote:
>>>> Ingo Molnar wrote:
>>>>> What we want here is two fold:
>>>>>
>>>>>      - enable kprobes event support when perf events is enabled and kprobes
>>>>>        is enabled. We dont want another config option for it.
>>>>
>>>> Sure, at least that combination should enable kprobe-tracer forcibly.
>>>
>>> Hmm, someone may not want to enables kprobe-tracer. Perhaps,
>>> "default y if (EVENT_PROFILE)" is enough, isn't it?
>>
>> Oops, this causes recursive dependency error :-(
>>
>> kernel/trace/Kconfig:90:error: found recursive dependency: TRACING ->
>> EVENT_TRACING ->  EVENT_PROFILE ->  KPROBE_TRACER ->  GENERIC_TRACER ->  TRACING
>
> This dependency problem can be resolved by simply making it 'default y'
> - the option itself depends on KPROBES already, which is default-off -
> so no need to also make it depend on EVENT_PROFILE.

OK,

> btw., it would be nice to re-name it to 'KPROBE_EVENTS'. If the probe
> point is used as a count - like in the __switch_to example i cited -
> there's no tracing going on at all.

Sure, it's not a tracer anyway :-)

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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