Re: [GIT PULL] tracing/kprobes: Add dynamic tracepoints + instruction decoder

Frederic Weisbecker
2009-08-27T15:25:44Z

On Thu, Aug 27, 2009 at 11:00:38AM -0400, Masami Hiramatsu wrote:
> Frederic Weisbecker wrote:
> > Ingo,
> >
> > This is the kprobes tracing pile of patches. I've tested it
> > successfully by setting some kprobes through debugfs by hand.
> >
> > It brings no known regressions.
> >
> > However, the stress test provided by Masami have revealed some
> > unstable points. Some symbols are unsafe to probe and raise
> > probing recursion.
> >
> > I've added a tiny patch in the series that helps identifying the
> > kprobe that has raised such situation.
> > For example it has learned me today that it's unsafe to trace
> > ret_from_exception() (obviously: it's on the int 3 handler path).
>
> Thank you, Frederic.
>
> I'm currently fixing those problems on x86-64 (on kvm).
> I'll also check it on x86-32, and fix it.
>
> Thanks

Cool.
Don't hesitate to interate through small patches that fix these
sites.

So that I can continue to test it over time and report you what I find,
may be I can try to fix some of them too.

I haven't fixed ret_from_exception because I wasn't sure about the
right thing to do: putting it in the kprobes section or blacklist its
name. It's a bit more delicate to put assembly code into sections so... :)