[lttng-dev] using --function/--probe

[trost@cloud.rain.com (Bill Trost)]

Hi,

I'm trying to investigate a problem under Linux 2.6.39.4 involving
kworker threads and am pretty much stymied. I've tried enabling
various events using --function and --probe and it's been
very hit or miss. Very often, "lttng enable-event" comes back
with nothing more specific than "bad ioctl", but every once
in a while I'll find a symbol I can add a probe point for.

So: What does "--probe" mean? What does "--function" mean, and how does
it differ from "--probe"? How do I determine what symbols are valid for
each of these options? And, maybe as a worked example, how do I
trace what work is being enqueued and run by the kworker threads?

Thanks,
Bill