I found a -current/i386 box apparently frozen this morning. It could not
fork/vfork any processes. Does the following explanation make sense?

The box has consdev on tty00. Among other things the mail server uses
syslog LOG_CONS,LOG_MAIL. syslogd -s was running and mail.* go to files,
yet the mail server messages were still written to /dev/console.
It seems that as nothing was reading /dev/console, the mail delivery
processes didn't exit, so processes piled up hitting the maxproc limit.

That seems to make sense, but I'm a little puzzled, as the box hasn't got
stuck before, yet had the same setup of serial console with nothing
plugged into the other end of the cable. Am I missing something?

Cheers,

Patrick