ttyflags wants to set some little flags on each tty.
These flags are LOCAL, CRTSCTS, SOFTCAR and MDMBUF.
To do so, it opens every physical tty listed in /etc/ttys with
open(path, O_RDONLY | O_NONBLOCK), does an ioctl to the mode, and
close it.
That ioctl should not block. It's right there, in the argument.
If that blocks, the driver has a bug.
My guess is that com.c has had a bug for a long time regarding non-existing
or bogus or otherwise weird hardware, and what has changed trust ACPI's tables
that there is an actual com device at a certain hardware address, and the
driver code trips over the device and goes into a non-returning loop.
What can I recommend?
change /etc/rc to do
ktrace -di -o /tmp/ktrace.out ttyflags -a &
add add something like
sleep 40
kdump -lf /tmp/ktrace.out
That might let us see it it hung on open() or in the ioctl()
