Noting down what we know about the ltp issue:

We've seen intermittent issues on the autobuilder where some ltp tests fail or 
hang. I've been trying to figure out how to reproduce the issue and narrow down
the cause.

I was able to isolate a patch which reproduces the issue for me:

http://git.yoctoproject.org/cgit.cgi/poky-contrib/commit/?h=rpurdie/t222&id=d7d65aae104caa03afc28837b0abe0b486d5a8b8

with master-next, setting:

IMAGE_INSTALL_append = ' ltp' 
TEST_SUITES = 'ping ssh ltp' 

then 

bitbake core-image-sato; bitbake core-image-sato -c testimage

where the issue shows up as a kernel "BUG:" in the logs in WORKDIR/testimage/qemu_*

The above patch runs the minimum of ltp tests I could find which replicate the issue.

I've reproduced this on 5.10.1 -> 5.10.42, 5.4.123 and 5.13-rc5.
(and we've ruled out linux-yocto with plain kernels)
Also reproduced on both qemu 6.0.0 and 5.2.0.

My build machine is an Ubuntu 20.04.2 LTS with:
Linux version 5.4.0-74-generic (buildd@lgw01-amd64-038) (gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04)) #83-Ubuntu SMP Sat May 8 02:35:39 UTC 2021

Cheers,

Richard