Improve missing tty handling in init(8)

[trasz]

Summary

Improve missing tty handling in init(8). This removes a check that did nothing - it was checking for ENXIO, which, with devfs, is no longer returned - and was badly placed anyway, and replaces it with similar one that works, and is done just before starting getty, instead of being done when rereading ttys.

From the practical point of view, this makes init(8) handle disappearing terminals (eg /dev/ttyU*) gracefully, without unneccessary getty restarts and resulting error messages.

[trasz]

Don't check if the device node exists for entries marked "on", as opposed to "onifexists" and "onifconsole".

[jilles]

lib/libc/gen/getttyent.3

121

typo: neccessarily should be necessarily

sbin/init/init.c

1517–1522

Is it indeed deliberate that this is an open() and not just a stat() or eaccess()?

[trasz]

lib/libc/gen/getttyent.3

121

Good catch, fixed. Thanks!

sbin/init/init.c

1517–1522

In theory this should be access(2), yeah. But in my testing the open(2) seems to work a bit better. Can't really explain it, but with access(2) you get false positives (zero return) every five attempts. In other words, I've been repeatedly plugging the USB serial dongle in and out, and with access(2) it seems to sometimes restart getty even when it shouldn't.