TTY code problems in current

[Roman Kurakin]

Hi,

    I observe some problems with my driver in async mode.
One of the panics I see is in function putc() from tty_subr.c.
It seems that this panic due to the fact that clist is not protected
by any locks if driver works in smpsafe mode without Giant.

    The panic occur beacuse of pointer modification (the new value
of the pointer eq. to NULL.
Any comments?

rik