Dear Lttng dev Team, I am currently interested in using lttng to measure the interrupt or hardware real-time latencies experienced within my user-space applications. Unfortunately I have been having issues installing lttng on my Raspberry Pi that is using the PREEMPT_RT patched kernel, version 4.14.91-rt49-v7+. The problems so far can be seen documented in the RPi Linux github forum page here: https://github.com/raspberrypi/linux/issues/2930
Initially I was about to just install the Debian package of the lttng onto the RPi, and just proceeded with the commands 'sudo apt-get install lttng-modules-dkms liblttng-ust-dev lttng-tools' However, I was unable to use lttng package at all and found out that for the RPi, a build from source is necessary for lttng, as described here: https://stackoverflow.com/questions/52386448/linux-trace-tool-lttng-on-raspbian-kernel-tracer-not-available Following their suggestion, I then tried to build the lttng packages from source, and even re-building the RPi kernel locally to ensure the kernel headers are in the RPi and linked up properly to the source packages. Unfortunately when I tried to do this for the lttng-modules package, it instead gave me the following warning in my latest attempt: In file included from /home/pi/BangEco_rvmscan/stagelight_project/lttng/lttng-modules/probes/lttng-kprobes.c:31:0: /home/pi/BangEco_rvmscan/stagelight_project/lttng/lttng-modules/probes/../blacklist/kprobes.h:19:4: error: #error "Your kernel is known to have buggy optimized kprobes implementation. Fixed by commit 0ac569bf6a7983c0c5747d6df8db9dc05bc92b6c \"ARM: 8834/1: Fix: kprobes: optimized kprobes illegal instruction\" in Linux. Disable CONFIG_OPTPROBES or upgrade your kernel." # error "Your kernel is known to have buggy optimized kprobes implementation. Fixed by commit 0ac569bf6a7983c0c5747d6df8db9dc05bc92b6c \"ARM: 8834/1: Fix: kprobes: optimized kprobes illegal instruction\" in Linux. Disable CONFIG_OPTPROBES or upgrade your kernel." I then tried to turn off the CONFIG_OPTPROBES kernel config, but it seemed to be automatically overwritten during kernel building and is considered an important part of the real-time RPi kernels. Has such problems been reported with this version of the PREEMPT_RT kernel in the past (again, the current kernel version that I am using is 4.14.91-rt49-v7+)? If there are I would like to know how this issue was resolved so that I can properly build and use the lttng package for my project. Thank you so much for your attention and looking forward to your reply soon. Best Regards, Nicholas Sadjoli
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