[lttng-dev] unable to add callstack-user context

Mathieu Desnoyers mathieu.desnoyers at efficios.com
Fri Jul 9 09:54:35 EDT 2021

----- On Jul 9, 2021, at 4:30 AM, lttng-dev <lttng-dev at lists.lttng.org> wrote: 

> Hi there, I'm a little new to lttng and tracing in general. I am using a Java
> Userspace agent, which is working well, but I am having trouble adding
> callstack context to my tracing channels. I'm not sure if it's relevant but
> running 'lttng add-context --list" shows callstack-user in the list.

It's not surprising, because the callstack-user context is specific to the kernel tracer. 

> the commands I input are:

> lttng create
> lttng enable-channel --userspace mychannel
> lttng enable-event --userspace --all --channel mychannel
> lttng add-context --userspace --channel mychannel --type callstack-user
> >Error: callstack-user: UST invalid context

This is expected. 

> When I run the following command instead:
> lttng add-context --userspace --channel mychannel --type vpid

> I am able to get it to work and I see vpid appear in my traces. Are there any
> other things I need to set up first to be able to use it?

> also, are there any commands that can list the per-domain contexts available?

Not currently, though I think it would make sense to make "lttng add-context --list" allow a tracing domain 
(e.g. --kernel/--userspace) to be specified as a future improvement. 

Some information about this is available in the lttng-add-context(1) man page, but the fact that the 
kernel and user callstack contexts are only supported by the kernel tracer don't seem to be mentioned. 



> _______________________________________________
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

Mathieu Desnoyers 
EfficiOS Inc. 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.lttng.org/pipermail/lttng-dev/attachments/20210709/d25ac344/attachment.htm>

More information about the lttng-dev mailing list