[lttng-dev] Error: Kernel create channel failed

[Deneau, Tom]

I seem to have gotten my lttng into a state where kernel tracing does not work.
I have tried uninstalling and reinstalling packages with no luck and also building from source.
Any suggestions welcome.

My distro is Ubuntu 16.04 but the kernel is 4.10.0-20-generic.

I have installed 2.9 using
apt install linux-tools-generic dkms
apt-add-repository ppa:lttng/stable-2.9
apt-get update
apt install -y lttng-tools liblttng-ust-dev  liblttng-ust-agent-java  python3-lttngust lttng-modules-dkms
wget http://ftp.us.debian.org/debian/pool/main/l/lttng-modules/lttng-modules-dkms_2.9.1-1_all.deb
dpkg -i lttng-modules-dkms_2.9.1-1_all.deb
apt install -y babeltrace python3-babeltrace

After lttng create test, I then try

# lttng -vvv enable-channel k -k --num-subbuf 64 --subbuf-size 512k
DEBUG1 - 08:27:54.415995 [13972/13972]: Channel subbuf num set to 64 (in cmd_enable_channels() at commands/enable_channels.c:420)
DEBUG1 - 08:27:54.416045 [13972/13972]: Channel subbuf size set to 524288 (in cmd_enable_channels() at commands/enable_channels.c:384)
DEBUG2 - 08:27:54.416080 [13972/13972]: Config file path found: /root (in _get_session_name() at utils.c:63)
DEBUG1 - 08:27:54.416087 [13972/13972]: Session name found: test (in _get_session_name() at utils.c:64)
DEBUG1 - 08:27:54.416099 [13972/13972]: Enabling channel k (in enable_channel() at commands/enable_channels.c:225)
DEBUG1 - 08:27:54.416129 [13972/13972]: LSM cmd type : 5 (in send_session_msg() at lttng-ctl.c:135)
Error: Channel k: Kernel create channel failed (session test)
Error: Command error
DEBUG1 - 08:27:54.416479 [13972/13972]: Clean exit (in clean_exit() at lttng.c:149)