First keypresses after boot being discarded

(Thread hijacked, subject changed)

On Wed, 26 Aug 2009, Ed Schouten wrote:
> People also reported issues to me where the first keypresses after the
> system has booted are discarded. I have yet to be convinced this is a
> TTY issue, not the keyboard code, interrupt handling, etc.

I've seen this, and might be able to offer some more information.  I 
booted 8.0-BETA2 from the same hard drive install on about 15 machines, 
and saw this problem on four of them, all identical motherboards.

In this setup, I had
"-D" in /boot.config
"console-comconsole" in /boot/loader/conf
ttyu0 enabled in /etc/ttys

I was then accessing them over the serial port.

When the machine had booted and was showing the "login:" prompt, sometimes 
input would be ignored from that point, and other times it would allow me 
to enter "root" but would hang on the enter.

Once it had hung, sometimes hammering the keyboard would bring it back, 
but the only reliable way of getting it to recover was to have the kernel 
print something out.  Luckily, the three LOR's often printed a minute or 
so after boot would do this, but unplugging/replugging (say) a USB 
keyboard so that the detection lines were printed would also free things 
up.

I don't know if that gives any clues as to where the problem lies.

Gavin