STREAMS tty driver problems..

[Leonard Sitongia]

In a previous article, sdl!monet!gregt at uunet.uu.net (Greg Tusar) writes:
>I'm in the process of writing a STREAMS tty driver, and I'm having a
>rather tough time of it. The driver is for an Omnibyte OB68K board which
>sits in a Sun 4/260 (SunOS 4.0.3)..
>
>The specific problem that I've run up against is that when a port is
>closed, and the stream is getting dismantled, something in qdetach()
>generates a data fault... My close routine is nowhere in the call stack
>trace. The actual call stack trace looks like this :

This is a known SunOS 4.0.3 bug.  Ask for the patch.  We were having this
problem also, with crashes up to 3 times a day, with the standard Sun
software, apparently because we have so many (?) serial ports (3 ALM-2
boards).

1025622	Panic bus error in streams close code

	The panic was being caused by a naive fix to #1019499, which
	introduced a race condition in the streams open/close code
	that could cause a stream to be torn down even though someone
	else was in the middle of opening it; the resulting corruption
	of data would cause the system to panic at some later time,
	normally after carrier was detected, getty opened the line,
	called vhangup, and closed the line. Specificly, the panic
	would occur most often during the "close" above, since the
	queue's q_qinfo pointer pointed at something unexpected. The
	fix is to back out the original fix for #1019499, and modify
	the streams code to properly handle the case of background
	processes holding a stream open that has been hung up.

Leonard E. Sitongia    System Programmer		 (303) 497-1509
Internet:               sitongia at hao.ucar.edu