Hello,
A bug has been reported[0] against a linux-5.15.y based Ubuntu kernel
that has the 5.15.79-rt54 real-time patch set applied.
This bug is causing a system hang when running disk tests with the
stress-ng[1] test suite. A 'hung task' call trace is being generated[2]
just prior to the system hanging. It appears the hang is happening
during a call to schedule.
To see if this was a regression, I also tested prior real-time patch
sets, going as far back to rt38 and all versions exhibit this bug. I
will test back further to see if this is in fact a regression and a
kernel bisect can be done. I also confirmed the same kernel without the
rt54 patch set applied does not exhibit this bug.
I will continue to debug this issue, but I wanted to send this message
upstream in case anyone else runs into it. Any specific tests, tracing
or debugging steps would be greatly appreciated. Otherwise, I'll report
back to this thread with any findings.
Thanks,
Joe
[0] https://bugs.launchpad.net/ubuntu-realtime/+bug/1998536
[1] https://github.com/ColinIanKing/stress-ng
[2] https://launchpadlibrarian.net/637058129/dmesg_dl110_rt_kernel.txt
