[lttng-dev] Userspace events not seen by kernel daemon?

[Mathieu Desnoyers]

* Thibault, Daniel (Daniel.Thibault at drdc-rddc.gc.ca) wrote:
>    I'm running an up-to-date LTTng suite (except for lttng-ust, where I'm using the 5 Mar 2013 20:17:22 commit). I've compiled the lttng-ust/doc/examples/easy-ust/sample application. While I run it (as a user *not* belonging to the tracing group), I notice something unexpected:
> 
> * The local session daemon lists the sample user-space event ('lttng list -u')
> * The kernel session daemon does not see the sample user-space event at all ('sudo lttng list -u ')

I guess you mean "per-user" rather than "local", and "system-wide"
rather than "kernel" here.

I will let Jeremie look into your question,

Thanks,

Mathieu

> 
>    It was my understanding that the kernel daemon should see all kernel and user-space events (for as many user-spaces as there might be).
> 
>    To test this further, I set up two traces using separate consoles.  The first is a user session:
> 
> $ lttng create usersession
> $ lttng enable-event -u --all
> 
>    The other is a kernel session:
> 
> $ sudo -H lttng create kernelsession
> $ sudo -H lttng enable-event -u --all
> $ sudo -H lttng enable-event -k sched_switch
> 
>    I start each session (respectively '$ lttng start' and '$ sudo -H lttng start') and the sample application (from a third console, '$ ./sample').  I wait until sample concludes, then shut down both sessions (respectively '$ lttng destroy' and '$ sudo -H lttng destroy').  Use of 'sudo -H' avoids current trace name collisions (contention over the .lttngrc file), as reported earlier on this list (but not filed as a bug...maybe I should do that too).
> 
>    The kernel trace contains no UST events, as can readily be discerned by the absence of a /ust branch in its folder structure.  This is confirmed by babeltrace, which sees some 245 000 kernel events and nothing else.  There are no missing events (babeltrace does not complain about skipped events, which it did with some other traces generated about the same time).  The System Monitor shows two lttng-sessiond daemons (one for me, another for root) and three lttng-consumerd daemons (one for me, two for root) as expected.
> 
>    What did I do wrong?
> 
> Daniel U. Thibault
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com