System V is Crashing

[Phil Chadwick]

In article <666 at brl-tgr.ARPA> mlip at nadc.ARPA (Michael Lipczynski) says:

    >A colleague of mine is trying to bring up AT&T's UNIX System V on a VAX
    >11/780.  Periodically, the system will crash and halt the CPU with the
    >following message:
    >
    >Machine software error: Protection violation on interrupt stack.

Our VAX 750 runs System V release 2 version 2.  I installed a new serial
printer and the system crashed (with a protection violation as above)
every time something was spooled to it.  I was experimenting with the
spooler interface program for this printer and changing the tty line
paramaters with ioctl to some unusual settings.  They were from memory:

	tio.c_iflag = IXON;
	tio.c_oflag = OPOST|ONLCR|NL1|CR3|TAB3|BS1|VT1|FF1;
	tio.c_cflag = B9600|CS8|CREAD;
	tio.c_lflag = 0;

By using crash(1m) I discovered zillions of entries in the callout array
which were to restart the printer's tty driver.  I can't remember the
exact circumstances, but I know that the callouts looked suspect and the
use of fill characters (add OFILL to tio.c_oflag above) for delays rather
than callouts cured the problem immediately.

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