systemtap 2.2.1 installcheck => kernel BUG at .. kprobes.c:707

[Frank Ch. Eigler]

Hi, Masami -

> I've found the root cause of this bug at last.

Thanks for looking into it!

> [...]
> This shouldn't happen if the probe unregistration is done AFTER
> kprobes_module_callback is called (because at that time the op
> is gone), and kprobe-tracer does it.
> So, ftrace never gets this bug, but systemtap does.

I don't quite understand.  In systemtap, as per runtime/transport/transport.c,
we use a notifier priority of 1 for the _stp_module_notifier, so that we get
notified after the kprobes_module_callback.  I believe this behavior matches
ftrace.


- FChE