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

From: Brian Hutchinson via lttng-dev <lttng-dev@lists.lttng.org>
To: lttng-dev@lists.lttng.org
Subject: [lttng-dev] I'm still getting empty ust traces using tracef
Date: Thu, 11 May 2023 11:53:01 -0400	[thread overview]
Message-ID: <CAFZh4h-Xsf7HGZ6A57BpuWH7CzogwV6D25vg05dOq30_MfxE0A@mail.gmail.com> (raw)

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
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