Cherry.Pasa@XEROX.ARPA (10/07/85)
I am having a problem which is difficult to track down. I am using Uniplus Sys 5.0 Unix. Problem: I get into an INTERMITTANT "feedback" type situation when using the same physical port for two different devices where only one device may run at a time. When this occurs and you invoke a cu to device tty5, the getty login to tty5m gets in and causes the port to cycle sending streams of characters (including some which really screw up the modem setup). What is happening is that when the cu process is opened, the characters typed at the terminal are output to tty5 and are received by tty5m where they are echoed back to tty5 which then echoes them back to the port where tty5m receives them and INSTA-LOOP. As I understand whats supposed to be happening is that each device which has a unique major-minor operates in its own memory environment. If this is so, and if the file locking mechanisms, ioctls, etc. are properly operating, this phenominea should not happen. We usually see this situation if the port has not been accessed for several days and then the initial command to the port is a cu command. Once the cu is issued, the only way found to date to stop the loop is to do a rm on both devices and physically remove all connections to the port. Only then can a SIG_HUP (kill -1), SIG_KILL (kill -9), or SIG_TERM (kill -15) be sent to stop the character stream loop. Has anybody seen this before and if so, can somebody explain why this doesn't happen all the time and/or what can be done to prevent it from happening at all. It only happens about 5 percent of time this port is used. It does happen to all ports configured in this manner. Setup: Where tty5 is a dial OUT ONLY port with a minor of 2 and where tty5m is a dial IN ONLY port with a minor of 130 (2 + 128) From /dev: protection owner group major minor device ------------ ------- ------- ------- ------- --------------- crw-rw-rw root root 12 2 /dev/tty5 crw-rw-rw uucp uucp 12 130 /dev/tty5m From /etc/inittab: t5::off:/etc/getty tty5 1200 t5m::respawn:/etc/getty tty5m 1200 From /etc/gettydefs: 1200# B1200 # B1200 CS8 CREAD IGNPAR ISTRIP ICRNL IXON IXANY ISIG ICANON ECHO ECHOE ECHOK OPOST ONLCR TAB1 #\r\n\n\xxxxxxxx\nlogin: #300 From /usr/lib/uucp/L-devices: DIR tty1 tty1 1200 ACUVENTEL tty1 tty1 1200 Hardware: CDC MB-1031 8-port Serial I/O Module; jumpers set for terminal set rather than data set. Ventel 212-3E modem with null modem interface between modem and MB-1031 Any ideas will be appreciated. B.C. & Zot------>* Cherry.PASA@Xerox.ARPA