[lttng-dev] Error: opening metadata failed (LTTng on OpenWRT)

[Robin Michielsen]

Hi all,

 

I am trying to trace the Linux kernel (system calls) using LTTng on a
platform that is running OpenWRT. I have cross compiled the latest versions
(2.10.x) of the lttng-modules, lttng-tools and lttng-ust packages and
installed these on my OpenWRT system. Now when I start a kernel trace then
the lttng tool returns the error "LTTng transport relay-metadata not found /
Error: Opening metadata failed". Does anybody know what might cause this
error, or have a hint on what to check?

 

I have attached the captured output of 'lttng-sessiond -vvv
--verbose-consumer'. Here is some more context:

.         MIPS platform running Linux 3.18.29

.         Package versions:

o   lttng-modules-2.10.4

o   lttng-tools-2.10.1

o   lttng-ust-2.10.0

.         lsmod shows that the following modules have been loaded:

o   lttng_clock

o   lttng_lib_ring_buffer

o   lttng_ring_buffer_client_discard

o   lttng_statedump

o   lttng_tracer

.         Commands to create and start a session:

o   lttng create

o   lttng enable-event --kernel --syscall open,close

o   lttng start

 

When 'lttng start' is called then lttng-sessiond's debug output shows
"Closing metadata fd -1 (in trace_kernel_destroy_metadata() at
trace-kernel.c:569)" followed by "Sending response (size: 20, retcode:
Opening metadata failed (45)) (in thread_manage_clients() at main.c:4641)".
I assume that the error that I'm seeing is because for some reason metadata
fd is being closed.

 

Does anybody know what may cause this issue, or have a hint on to check?

 

Kind regards,

Robin

 

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