dtrace sdt problem: my fault or a generic problem (SYSINIT not
working as expected for modules)?
Alexander Leidinger
Alexander at Leidinger.net
Fri Mar 25 13:15:05 UTC 2011
Quoting Andriy Gapon <avg at freebsd.org> (from Fri, 25 Mar 2011 12:56:56 +0200):
> on 25/03/2011 11:52 Alexander Leidinger said the following:
>> As I read it, it looks a little bit like the SYSINIT of the SDT
>> probes didn't
>> work as expected for my new probes (does this work in modules?
>> fxr.watson.org
>> AFAICS only lists SDT probes in kernel-code, not in module-code), a
>> hit with the
>> clue-bat is welcome.
>
> My reading of the code is that all modules with SDT proivders/probes
> should be
> loaded before sdt module itself.
> SYSINIT in your module(s) works as expect, but dtrace_register() is
> not called
> on your SDT provider. See sys/cddl/dev/sdt/sdt.c for details:
> sdt_modevent ->
> sdt_load -> sdt_provider_listall(sdt_provider_reg_callback) ->
> dtrace_register.
So if I load linux.ko before sdt.ko, or if I unload sdt.ko and reload
it, it should work? I'm going to try this after sending this mail.
> I am not saying that this behavior is correct/desired, just that
> this is what we
> have now.
Is someone working on this? If not, what would be a solution for this?
Adding a call (which one) to the modevent of the module which is using
SDT probes?
Can we prevent a kernel panic for this case (maybe detecting a NULL ID
and skipping... or maybe even registering it)?
Something to add to the ideas list as a GSoC entry, or is this too small/big?
Bye,
Alexander.
--
One way to make your old car run better is to look up the price of a
new model.
http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID = B0063FE7
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