[lttng-dev] Using lttng 2.11 and UST doesn't appear to work - getting empty trace files

[Brian Hutchinson]

Hi,

I'm on an embedded platform, i.MX8 using Lttng 2.11 with 5.6.69 kernel.

Tracing kernel events with lttng works fine but userspace (tracef and trace
provider type tracing) appears to have an issue I can't figure out.

systemd is starting up my application ( a bunch of processes and threads on
multiple cpu's) on boot.

I'm statically compiling and linking in lttng-ust.  If I use just tracef
type tracing, when I do lttng list --userspace I get nothing.  If I add in
a trace provider and a tracepoint, then I see my trace provider tracepoint
and:

     lttng_ust_tracelog:TRACE_DEBUG (loglevel: TRACE_DEBUG (14)) (type:
tracepoint)
     lttng_ust_tracelog:TRACE_DEBUG_LINE (loglevel: TRACE_DEBUG_LINE (13))
(type: tracepoint)
     lttng_ust_tracelog:TRACE_DEBUG_FUNCTION (loglevel:
TRACE_DEBUG_FUNCTION (12)) (type: tracepoint)
     lttng_ust_tracelog:TRACE_DEBUG_UNIT (loglevel: TRACE_DEBUG_UNIT (11))
(type: tracepoint)
     lttng_ust_tracelog:TRACE_DEBUG_MODULE (loglevel: TRACE_DEBUG_MODULE
(10)) (type: tracepoint)
     lttng_ust_tracelog:TRACE_DEBUG_PROCESS (loglevel: TRACE_DEBUG_PROCESS
(9)) (type: tracepoint)
     lttng_ust_tracelog:TRACE_DEBUG_PROGRAM (loglevel: TRACE_DEBUG_PROGRAM
(8)) (type: tracepoint)
     lttng_ust_tracelog:TRACE_DEBUG_SYSTEM (loglevel: TRACE_DEBUG_SYSTEM
(7)) (type: tracepoint)
     lttng_ust_tracelog:TRACE_INFO (loglevel: TRACE_INFO (6)) (type:
tracepoint)
     lttng_ust_tracelog:TRACE_NOTICE (loglevel: TRACE_NOTICE (5)) (type:
tracepoint)
     lttng_ust_tracelog:TRACE_WARNING (loglevel: TRACE_WARNING (4)) (type:
tracepoint)
     lttng_ust_tracelog:TRACE_ERR (loglevel: TRACE_ERR (3)) (type:
tracepoint)
     lttng_ust_tracelog:TRACE_CRIT (loglevel: TRACE_CRIT (2)) (type:
tracepoint)
     lttng_ust_tracelog:TRACE_ALERT (loglevel: TRACE_ALERT (1)) (type:
tracepoint)
     lttng_ust_tracelog:TRACE_EMERG (loglevel: TRACE_EMERG (0)) (type:
tracepoint)
     lttng_ust_tracef:event (loglevel: TRACE_DEBUG (14)) (type: tracepoint)
     lttng_ust_lib:unload (loglevel: TRACE_DEBUG_LINE (13)) (type:
tracepoint)
     lttng_ust_lib:debug_link (loglevel: TRACE_DEBUG_LINE (13)) (type:
tracepoint)
     lttng_ust_lib:build_id (loglevel: TRACE_DEBUG_LINE (13)) (type:
tracepoint)
     lttng_ust_lib:load (loglevel: TRACE_DEBUG_LINE (13)) (type:
tracepoint)
     lttng_ust_statedump:end (loglevel: TRACE_DEBUG_LINE (13)) (type:
tracepoint)
     lttng_ust_statedump:debug_link (loglevel: TRACE_DEBUG_LINE (13))
(type: tracepoint)
     lttng_ust_statedump:build_id (loglevel: TRACE_DEBUG_LINE (13)) (type:
tracepoint)
     lttng_ust_statedump:bin_info (loglevel: TRACE_DEBUG_LINE (13)) (type:
tracepoint)
     lttng_ust_statedump:start (loglevel: TRACE_DEBUG_LINE (13)) (type:
tracepoint)

When I do lttng start, I get a directory structure in the trace directory
but the file sizes do not ever increase.  It's just a directory structure
with files created and then that's it, no events being written to the
files.  At first I thought things just weren't linked in right and not
working but then discovered how to run lttng-sessiond in -vvv mode and then
could see lots of things are going on, tracing appears to be trying to work
as there is tons of activity being output by lttng-sessiond, but like I
said the trace files aren't being added to.

I looked at the lttng-sessiond log I captured and can't quite make out the
problem so attaching it.

I'm probably not doing something right but can't figure out what that is so
any pointers appreciated.

Regards,

Brian
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