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

* 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


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