K 10
svn:author
V 3
ian
K 8
svn:date
V 27
2017-01-13T16:37:38.383925Z
K 7
svn:log
V 483
Check tty_gone() after allocating IO buffers.  The tty lock has to be
dropped then reacquired due to using M_WAITOK, which opens a window in
which the tty device can disappear.  Check for this and return ENXIO
back up the call chain so that callers can cope.

This closes a race where TF_GONE would get set while buffers were being
allocated as part of ttydev_open(), causing a subsequent call to
ttydevsw_modem() later in ttydev_open() to assert.

Reported by:	pho
Reviewed by:	kib

END