[lttng-dev] I'm still getting empty ust traces using tracef

Mathieu Desnoyers mathieu.desnoyers at efficios.com
Thu May 11 14:13:00 EDT 2023

On 2023-05-11 12:36, Brian Hutchinson via lttng-dev wrote:
> ... more background.  I've always used ltt in the kernel so I don't
> have much experience with the user side of it and especially
> multi-threaded, multi-core so I'm probably missing some fundamental
> concepts that I need to understand.

Which are the exact versions of LTTng-UST and LTTng-Tools you are using 
now ? (2.13.N or which git commit ?)



> Regards,
> Brian
> On Thu, May 11, 2023 at 11:53 AM Brian Hutchinson <b.hutchman at gmail.com> wrote:
>> Hi,
>> I posted a while ago (thread - Using lttng 2.11 and UST doesn't appear
>> to work - getting empty trace files) about this problem I'm having
>> with getting empty trace logs.
>> I've since upgraded to lttng v2.13 and while I can do a simple hello
>> world program with tracef and get events in the log files, my more
>> complicated large multi-threaded app I'm trying to debug is still
>> getting empty log file traces.
>> I can list the user space events in my app.
>> Next I do:
>> lttng enable-event --userspace 'lttng_ust_tracef:*'
>> ... to enable the events, start lttng, start my app, .... and I get a
>> trace directory structure that's empty.
>> I feel like I've read every thread in the archives about people having
>> the same problem.
>> I did try using LD_PRELOAD with various libs thinking that was the
>> problem but so far I'm still getting empty traces.
>> So far I've tried:
>> LD_PRELOAD=liblttng-ust-libc-wrapper.so.1:liblttng-ust-pthread-wrapper.so.1:liblttng-ust-dl.so.1:liblttng-ust-fork.so.1:liblttng-ust-fd.so.1
>> /usr/local/bin/my_app
>> I guess one question I have is how do I determine which "helper libs"
>> I need to preload?
>> The application I'm working on is made up of a bunch of smaller static
>> libs linked together into one big executable and that is linked with
>> -llttng-ust and -ldl.
>> I'm pretty stuck at the moment.  Anyone have any wisdom on what I
>> might be doing wrong or how I can tell why I'm not getting events in
>> the logs?
>> Thanks,
>> Brian
> _______________________________________________
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

Mathieu Desnoyers
EfficiOS Inc.

More information about the lttng-dev mailing list