[lttng-dev] make a trace_event in a module (driver)

[Jérémie Galarneau]

On Mon, Nov 25, 2013 at 10:53 AM, Thibault, Daniel
<Daniel.Thibault at drdc-rddc.gc.ca> wrote:
>> Date: Sun, 24 Nov 2013 19:26:05 +0100
>> From: Klaus Dannecker <klaus.dannecker at gmx.de>
>>
>> > Interesting. Would you mind running "lttng start" in verbose mode and
>> > provide the output?
>> > lttng -vvv start
>> klaus at ubuntu:~$ sudo lttng -vvv start
>> DEBUG2 [2854/2854]: Config file path found: /home/klaus (in get_session_name() at utils.c:57)
>> DEBUG1 [2854/2854]: Session name found: auto-20131124-091639 (in get_session_name() at utils.c:58)
>> DEBUG1 [2854/2854]: Starting tracing for session auto-20131124-091639 (in start_tracing() at commands/start.c:81)
>> DEBUG1 [2854/2854]: LSM cmd type : 16 (in send_session_msg() at lttng-ctl.c:131)
>> 'ctrl c'
>> klaus at ubuntu:~$
>
> Definitely looks like a module loading problem.
>
>> > lttng-modules does not define an "uninstall" make target. I guess
>> > you'll have to delete the modules manually under /lib/modules/$(uname
>> > -r)/extra /lib/modules/$(uname -r)/extra/lib /lib/modules/$(uname
>> > -r)/extra/probes
>> >
>> > I'm wondering if it could be a conflict with your distribution's
>> > lttng-modules-dkms package... Could you verify that it is not
>> > installed?
>>
>> now i make two experiments:
>> first:
>> install ubuntu 12.04 in vmware
>> $ git clone git://git.lttng.org/lttng-tools.git
>> $ git clone git://git.lttng.org/lttng-modules.git
>> $ git clone git://git.lttng.org/lttng-ust.git
>> $ git clone git://git.lttng.org/userspace-rcu.git
>> compile and install all like:
>> https://www.ibm.com/developerworks/community/blogs/fe313521-2e95-46f2-817d-44a4f27eba32/entry/howto_tracing_with_lttng?lang=en
>> now i have the same problem.
>
>    Aha!  There is one crucial mistake in the ibm.com document: he installs the packages in the wrong order.  lttng-tools must be installed AFTER lttng-modules and lttng-ust.  lttng-modules can be installed before, during or after lttng-ust, but userspace-rcu must be installed before lttng-ust.
>    The problem is that the configure of lttng-tools detects the presence or absence of lttng-modules and also detects the presence or absence of lttng-ust, and adjusts to both.  By installing lttng-tools before lttng-modules, you've built an lttng-tools set that CANNOT be used to trace the kernel.
>
>    So, try again from scratch, making sure to install lttng-tools last.
>

lttng-tools checks for kernel modules at run time, not at configure
time. You can safely install lttng-modules after lttng-tools and still
use kernel tracing.

Regards,
Jérémie

>> second:
>> install ubuntu 12.04 in vmware
>> sudo apt-get install lttng-tools
>>...
>> Building only for 3.8.0-29-generic
>> Building initial module for 3.8.0-29-generic
>> Error! Bad return status for module build on kernel: 3.8.0-29-generic (i686)
>> Consult /var/lib/dkms/lttng-modules/2.0.2/build/make.log for more information.
>> Setting up lttng-tools (2.0.1-0ubuntu1) ...
>> /usr/sbin/addgroup
>> lttng-sessiond start/running, process 5515
>> Processing triggers for libc-bin ...
>> ldconfig deferred processing now taking place
>> klaus at ubuntu:~$
>
>    The Ubuntu lttng 2.0.1 install will very likely run into trouble against kernel 3.8 because of the new module signing requirements.
>
>> $ git clone git://git.lttng.org/lttng-modules.git
>> compile and install lttng_modules
>>
>> now works lttng start, stop and destroy!
>>
>> Klaus
>
> Daniel U. Thibault
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-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com