signals - tty line discipline

[Allan Statham]

----- News saved at 20 Sep 89 10:56:35 GMT
  I have recently discovered a problem related to tty device driver signals
e.g SIGHUP , not being passed back to the controlling process. This situation
occurs when a process opens,closes and re-opens a tty device using the same
common line discipline code. Setpgrp() is performed before each open.
The problem is due to the statements:-

	u.u_ttyp = &tp->t_pgrp;
	tp->t_pgrp = pp->p_pgrp;

in the line discipline ttyopen() routine not being executed. This is caused by
the fact that u.u_ttyp is not NULL on the 2nd and subsequent opens of any
tty device using the same common line discipline code.
  A possible solution to this problem would be to insure that u.u_ttyp is set
to NULL in the ttclose() routine before exiting. Could anyone who has any
thoughts on this problem please mail me on: bilbo at fulcrum.bt.co.uk