[lttng-dev] lttng-dev Digest, Vol 60, Issue 31

Thibault, Daniel Daniel.Thibault at drdc-rddc.gc.ca
Thu Apr 18 15:26:20 EDT 2013

>   Absolutely: no patching required.

   I decided to find out if the lttng-modules were required at all if one needs to do only user-space tracing.

   I installed (on an otherwise lttng-virgin system) just the userspace-rcu, lttng-ust, and lttng-tools packages.  The lttng commands fail for the usual "can't find /usr/local/lib" reason, so I need to do not:

$ lttng list -u

   but rather

$ LD_PRELOAD=/usr/local/lib/liblttng-ctl.so:/usr/local/lib/liblttng-ust-ctl.so lttng list -u


$ LD_LIBRARY_PATH=/usr/local/lib lttng list -u

   However, once I made the lttng-ust/doc/examples/easy-ust sample, I get a segmentation fault/core dump after starting the trace.

$ LD_LIBRARY_PATH=/usr/local/lib lttng create usttrace
Session usttrace created.
Traces will be written in /home/daniel/lttng-traces/usttrace-20130418-150106
$ LD_LIBRARY_PATH=/usr/local/lib lttng enable-event -u --all
All UST events are enabled in channel channel0
$ LD_LIBRARY_PATH=/usr/local/lib lttng start
Tracing started for session usttrace
$ LD_LIBRARY_PATH=/usr/local/lib ./sample
Segmentation fault (core dumped)

   Is this supposed to work or are the kernel modules required even when doing just pure user-space tracing?  I did get a partial trace on disk (just the channel0_0 and metadata files, no events in them).

Daniel U. Thibault
R & D pour la défense Canada - Valcartier (RDDC Valcartier) / Defence R&D Canada - Valcartier (DRDC Valcartier)
Cyber sécurité pour les missions essentielles (CME) / Mission Critical Cyber Security (MCCS)
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