Re: [PATCH -tip v5 0/7] tracing: kprobe-based event tracer and x86 instruction decoder

Ingo Molnar
2009-05-11T21:48:14Z

* Masami Hiramatsu <mhiramat@redhat.com> wrote:

> Steven Rostedt wrote:
> > On Mon, 11 May 2009, Masami Hiramatsu wrote:
> >>> Two high-level comments:
> >>>
> >>> - There's no self-test - would it be possible to add one? See
> >>> trace_selftest* in kernel/trace/
> >> I'm not so sure. Currently, it seems that those self-tests are
> >> only for tracers which define new event-entry on ring-buffer.
> >> Since this tracer just use ftrace_bprintk, it might need
> >> another kind of selftest. e.g. comparing outputs with
> >> expected patterns.
> >> In that case, would it be better to make a user-space self test
> >> including filters and tracepoints?
> >
> > Or have the workings in the selftest in kernel. As if a user started it.
> > It does not need to write to the ring buffer, that is just what I did. The
> > event selftests don't check if anything was written to the ring buffer,
> > they just make sure that the tests don't crash the system.
>
> Would you mean that it is enough to enable some probes and just
> see what happened at boot time?
> That's so easy to add.

Yes, that's the idea!

Try to think of regressions/crashes/misbehavior you generally
trigger while you developed kprobes, and try to add a reasonable set
of probes that test the code from those angles.

It doesnt have to be a full, complex test-suite, but even just 80%
of coverage of functionality keeps 4/5th of all regressions out of
the kernel at a very early stage ...

Ingo