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

[Jonathan Rajotte-Julien]

Hi,

On Thu, Nov 23, 2017 at 06:20:24PM +0100, Robin Michielsen wrote:
> Hi Jonathan,
> 
> The lttng-sessiond.log that I provided was actually from a second time that I started 'lttng-sessiond'  (did not realize that there is a difference), which resulted in the already loaded error. When I captured the output from a fresh start of 'lttng-sessiond' I noticed lots of modprobe errors with modules that could not be loaded.

Normally, lttng-sessiond will unload the module it loaded on start if a clean
teardown is initiated (SIGTERM).

> 
> Turns out that the modprobe on my OpenWrt system can only handle modules with a name of max 32 characters (!). The first mandatory core module ("lttng-ring-buffer-client-discard") is still loaded as its name is exactly 32 chars, the other 5 core modules do not get loaded as their names are longer than 32 chars. I will modify modprobe as a proper fix, but shortening the names of the lttng-*.ko modules and manually loading each core module already showed that this solves the issue.

Glad I could help. :P I'm curious could you point me to the modprobe code that
openWRT uses?

Cheers!

> 
> Thanks for your reply! This helped in pointing me in the right direction.
> 
> Kind regards,
> Robin
> 
 
-- 
Jonathan Rajotte-Julien
EfficiOS