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

[Masami Hiramatsu <mhiramat at redhat dot com>]

Ingo Molnar wrote:
> * 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.

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@redhat.com