Re: [PATCH -tip v5 00/10] kprobes: Kprobes jump optimization support

Ingo Molnar
2009-11-24T07:53:37Z

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Tue, Nov 24, 2009 at 03:03:19AM +0100, Frederic Weisbecker wrote:
> > On Mon, Nov 23, 2009 at 06:21:16PM -0500, Masami Hiramatsu wrote:
> > > When the optimized-kprobe is hit before optimization, its handler
> > > changes IP(instruction pointer) to copied code and exits. So, the
> > > instructions which were copied to detour buffer are executed on the detour
> > > buffer.
> >
> >
> >
> > Hm, why is it playing such hybrid game there?
> > If I understand well, we have executed int 3, executed the
> > handler and we jump back to the detour buffer?
> >
>
> I got it, I think. We have instructions to patch. And the above turn
> this area into dead code, safe to patch.
>
> But still, stop_machine() seem to make it not necessary anymore.

i think 'sending an IPI to all online CPUs' might be an adequate
sequence to make sure patching effects have propagated. I.e. an
smp_call_function() with a dummy function?

Ingo