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Re: [PATCH -tip perf/probes 00/10] x86 insn decoder bugfixes and perf-probe syntax changes
- From: Ingo Molnar <mingo at elte dot hu>
- To: Masami Hiramatsu <mhiramat at redhat dot com>
- Cc: Arnaldo Carvalho de Melo <acme at redhat dot com>, Frédéric Weisbecker <fweisbec at gmail dot com>, lkml <linux-kernel at vger dot kernel dot org>, Steven Rostedt <rostedt at goodmis dot org>, Jim Keniston <jkenisto at us dot ibm dot com>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Christoph Hellwig <hch at infradead dot org>, "Frank Ch. Eigler" <fche at redhat dot com>, "H. Peter Anvin" <hpa at zytor dot com>, Jason Baron <jbaron at redhat dot com>, "K.Prasad" <prasad at linux dot vnet dot ibm dot com>, Peter Zijlstra <peterz at infradead dot org>, Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>, systemtap <systemtap at sources dot redhat dot com>, DLE <dle-develop at lists dot sourceforge dot net>
- Date: Tue, 3 Nov 2009 08:32:36 +0100
- Subject: Re: [PATCH -tip perf/probes 00/10] x86 insn decoder bugfixes and perf-probe syntax changes
- References: <20091027204156.30545.96425.stgit@harusame> <20091029085348.GD26970@elte.hu> <4AE9C919.4070003@redhat.com> <4AEF4C29.2060501@redhat.com> <4AEF7B22.50705@redhat.com>
* Masami Hiramatsu <mhiramat@redhat.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.
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.
Ingo