[lttng-dev] example/demo not working

[Jonathan Rajotte Julien]

Hi Ashish,

On 2016-05-24 09:29 AM, Ashish Sangwan wrote:
> Hi,
>
> I am trying to use lttng library to trace user space.
> I have installed the packages on Ubuntu as mentioned here :
> http://lttng.org/download/#ubuntu
> Also, I have download the git snapshot from
> http://git.lttng.org/?p=lttng-ust.git;a=snapshot;h=HEAD;sf=tgz and
> built the sources.

Since you look interested in the latest lttng-ust I would recommend you 
install the latest version of all the projects.
The lttng-modules, lttng-ust and lttng-tools projects work in lockstep 
mode so if you plan on using lttng-ust 2.8 I highly recommend using 
lttng-modules and lttng-tools 2.8.

We just released the 2.8 stable branch so you might want to use this.

Babeltrace and userspace-rcu are independent so any recent version 
should be good.

>
> When I am trying to execute any of the application in example
> directory I am not able to get the trace.
> I have added myself to the tracing group using usermod and than did
> the following:
> ashish at ashish-pc:~/lttng/lttng-ust-HEAD-f4624de/doc/examples/demo-tracelog$ pwd
> /home/ashish/lttng/lttng-ust-HEAD-f4624de/doc/examples/demo-tracelog

I'm not sure if you compiled and installed lttng-ust HEAD or simply used 
the provided example.

If you only used the example I would recommend to checkout the 2.4 
branch since it seems to be the version you installed.
I would recommend that you use the ppa to obtain a more recent version 
of the tool set.

Cheers

> lttng create
> lttng enable-event -u "lttng_ust_tracelog:*"
> lttng start
> ./demo-tracelog
> lttng stop
>
> All the above commands were successfully completed. But when I am
> trying to view the trace I am getting error.
>
> ashish at ashish-pc:~/lttng/lttng-ust-HEAD-f4624de/doc/examples/demo-tracelog$
> lttng view
> Trace directory: /home/ashish/lttng-traces/auto-20160524-185123
>
> [error] Cannot open any trace for reading.
>
> [error] opening trace "/home/ashish/lttng-traces/auto-20160524-185123"
> for reading.
>
> [error] none of the specified trace paths could be opened.
>
> ashish at ashish-pc:~/lttng/lttng-ust-HEAD-f4624de/doc/examples/demo-tracelog$
> lttng destroy
> Session auto-20160524-185123 destroyed
>
> I will appreciate any help.
>
> Regards,
> Ashish
>
> PS: BTW, installing lttng-modules-dkms failed for me (kernel version
> 3.19) with below error:
>   DKMS make.log for lttng-modules-2.4.0 for kernel 3.19.0-31-generic (x86_64)
>   Tue May 24 18:55:21 IST 2016
>   make: Entering directory `/usr/src/linux-headers-3.19.0-31-generic'
>     CC [M]  /var/lib/dkms/lttng-modules/2.4.0/build/lttng-ring-buffer-client-discard.o
>   In file included from
> /var/lib/dkms/lttng-modules/2.4.0/build/wrapper/ringbuffer/../../lib/ringbuffer/../../wrapper/ringbuffer/frontend_api.h:1:0,
>                    from
> /var/lib/dkms/lttng-modules/2.4.0/build/wrapper/ringbuffer/../../lib/ringbuffer/api.h:35,
>                    from
> /var/lib/dkms/lttng-modules/2.4.0/build/wrapper/ringbuffer/api.h:1,
>                    from
> /var/lib/dkms/lttng-modules/2.4.0/build/lttng-ring-buffer-client.h:175,
>                    from
> /var/lib/dkms/lttng-modules/2.4.0/build/lttng-ring-buffer-client-discard.c:29:
>   /var/lib/dkms/lttng-modules/2.4.0/build/wrapper/ringbuffer/../../lib/ringbuffer/../../wrapper/ringbuffer/../../lib/ringbuffer/frontend_api.h:
> In function ‘lib_ring_buffer_put_cpu’:
>   /var/lib/dkms/lttng-modules/2.4.0/build/wrapper/ringbuffer/../../lib/ringbuffer/../../wrapper/ringbuffer/../../lib/ringbuffer/frontend_api.h:76:2:
> error: implicit declaration of function ‘__get_cpu_var
>   ’ [-Werror=implicit-function-declaration]
>     __get_cpu_var(lib_ring_buffer_nesting)--;
>     ^
>   /var/lib/dkms/lttng-modules/2.4.0/build/wrapper/ringbuffer/../../lib/ringbuffer/../../wrapper/ringbuffer/../../lib/ringbuffer/frontend_api.h:76:40:
> error: lvalue required as decrement operand
>     __get_cpu_var(lib_ring_buffer_nesting)--;
>                                           ^
>   cc1: some warnings being treated as errors
>   make[1]: *** [/var/lib/dkms/lttng-modules/2.4.0/build/lttng-ring-buffer-client-discard.o]
> Error 1
>   make: *** [_module_/var/lib/dkms/lttng-modules/2.4.0/build] Error 2
>   make: Leaving directory `/usr/src/linux-headers-3.19.0-31-generic'
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-- 
Jonathan R. Julien
Efficios