[lttng-dev] Enable UST probes only in specific process

[Thibault, Daniel]

----------------------------------------------------------------------
Date: Wed, 30 Jul 2014 17:58:25 +0400
From: Dmitri Shubin <sbn at tbricks.com>

> Is it possible to enable user-space tracepoint in specific process (of given PID)?
>
> AFAIU
> lttng enable-event -u prov:probe --filter '$ctx.vpid==12345'
> enables probe for all processes and then drops unmatched.
>
> In my case I'm doing rather heavyweight thing in probe (getting stack
> trace) and want to do that only in the process of interest.
>
> Is it possible?
>
> The only way I can do it now is playing with LTTNG_HOME variable setting it to different paths for each process.

   I do believe that the filter drops the event before it starts resolving its arguments, so filtering should be enough.  Someone more familiar with the internals of LTTng should set us straight either way.

Daniel U. Thibault
Protection des systèmes et contremesures (PSC) | Systems Protection & Countermeasures (SPC)
Cyber sécurité pour les missions essentielles (CME) | Mission Critical Cyber Security (MCCS)
RDDC - Centre de recherches de Valcartier | DRDC - Valcartier Research Centre
2459 route de la Bravoure
Québec QC  G3J 1X5
CANADA
Vox : (418) 844-4000 x4245
Fax : (418) 844-4538
NAC : 918V QSDJ <http://www.travelgis.com/map.asp?addr=918V%20QSDJ>
Gouvernement du Canada | Government of Canada
<http://www.valcartier.drdc-rddc.gc.ca/>