[lttng-dev] No trace files are generated for UST

Manikandan Govindaswamy magov at vestas.com
Fri Dec 6 10:51:54 EST 2013

Yes, with that LD_PRELOAD sample able to run.

root@/tmp/lttng-build-root/bin # ./lttng create app
Session app created.
Traces will be written in /root/lttng-traces/app-20131206-174935
root@/tmp/lttng-build-root/bin # dmesg
root@/tmp/lttng-build-root/bin # ./lttng enable-event -u -a
All UST events are enabled in channel channel0
root@/tmp/lttng-build-root/bin # ./lttng start
Tracing started for session app
root@/tmp/lttng-build-root/bin # cd ..
root@/tmp/lttng-build-root # cd ..
root@/tmp # LD_PRELOAD=/tmp/lttng-build-root/lib/liblttng-ust.so.0 ./sample
root@/tmp #
root@/tmp #
root@/tmp # cd lttng-build-root/
root@/tmp/lttng-build-root # cd bin/
root@/tmp/lttng-build-root/bin # ./lttng stop
Waiting for data availability
Tracing stopped for session app
root@/tmp/lttng-build-root/bin # dmesg
root@/tmp/lttng-build-root/bin # ./lttng destroy
Session app destroyed
root@/tmp/lttng-build-root/bin # cd /
root@/ # cd root/
root@~ # ls
root@~ # cd lttng-traces/
root@~/lttng-traces # ls
root@~/lttng-traces #< no traces are generated>

in ps -ef

28664 root       0:00 ./lttng-sessiond -vvv --consumerd64-path=/tmp/lttng-build-root/lib/lttng/libexec/lttng-consumerd
29027 root       0:00 lttng-consumerd --quiet -u --consumerd-cmd-sock /var/run/lttng/ustconsumerd64/command --consumerd-err-sock /var/run/lttng/ustconsumerd64/error


-----Original Message-----
From: Thibault, Daniel [mailto:Daniel.Thibault at drdc-rddc.gc.ca] 
Sent: Friday, December 06, 2013 9:14 PM
To: Manikandan Govindaswamy; Jérémie Galarneau
Cc: lttng-dev at lists.lttng.org
Subject: RE: [lttng-dev] No trace files are generated for UST

> As I'm using the custom image on x86 machine, i've kept the lib in /tmp/lttng-build-root/lib folder and this sample able to see the library as well.
> And the same way I able to create the trace files for kernel but not for ust. There were no dmesg as well.
> [...]
> root@/tmp # ldd sample
>         linux-vdso.so.1 (0x00007fff2a135000)
>         libdl.so.2 => /lib64/libdl.so.2 (0x00007fe2cccb5000)
>         liblttng-ust.so.0 => /tmp/lttng-build-root/lib/liblttng-ust.so.0 (0x00007fe2cca51000)
>         [...]

   Try running sample using:

LD_PRELOAD=/tmp/lttng-build-root/lib/liblttng-ust.so.0 ./sample

   If the LD_PRELOAD succeeds, we will know at least that liblttng-ust is reachable by sample.

   The modules have nothing to do with UST: kernel and user-space tracing are essentially independent features.

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)
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