So I invoked
echo 'bt/t 0t<PID>' | crash
ten times for both PIDs.
The process that got stuck first has either
_KERNEL_OPT_MEMORY_RBFLAGS() at ffff97a14cbbe818
Bad user frame pointer: 0xffff979ed96a48c0
or
__kernel_end() at 0
Bad user frame pointer: 0xffff979ed96a48c0
and the one that got stuck second has
__kernel_end() at 0
_KERNEL_OPT_GENFB_GLYPHCACHE() at _KERNEL_OPT_ACPI_SCANPCI
with an optional additional
Bad user frame pointer: 0xffff97a026d31204
