Broken tty handling

David Ford (david@linux.com)
Sun, 7 Jan 2001 22:04:43 -0800 (PST)


Every once in a while I have a very frustrating problem develop. All tty
handling stops. Packets flow in and out of the machine fine, but anything
with a tty halts. I don't know exactly what is happening but I have found
that killing the last user that logged in (all his processes) usually fixes
everything.

It just happened to me and I realize this is vague but there's nothing I
have been able to attribute it to other than a problem in tty handling. I
know it isn't ssh v.s. telnet v.s. xyz because it doesn't matter, they all
stall.

Here's the data I had. Aaron was the last person to log in when it broke, I
was the first after it broke.

# grep aaron brokettyspseo
aaron 22843 do_adj -bash
aaron 22865 write_ pine
aaron 23211 do_adj -bash
aaron 23228 tty_wa stty icanon echo
aaron 23277 read_c -bash

# w|grep aaron
.aaron pts/13 dur-cas1-cs-26.d 9:12pm 26:44 0.14s 0.10s pine
.aaron pts/14 dur-cas1-cs-26.d 9:28pm 15:09 0.01s 0.01s -bash
.aaron pts/15 dur-cas1-cs-26.d 9:29pm 14:26 0.06s 0.06s -bash

An 'skill aaron' didn't solve it but 'skill -9 aaron' did.

Here's a snippet from my /etc/profile which the stty from above comes into
play:

# does the user want his titlebar set?
if [ "x$TITLEBAR" = "xyes" ]; then
echo -ne Checking for titlebar capability
stty -icanon -echo min 0 time 20
echo -ne '\033[7n'
read term_id
display=$(echo $term_id|sed '/.*:0/!d')
if [ x$display != x ]; then
PS1='\[\033]2; ($(date +%l:%M%p)) \u@\h \w\007\033]1;\u@\h\007\]\$ '
else
PS1='\h:\w\$ '
fi
echo -ne '\033[2K\r'
stty icanon echo
else
PS1='\h:\w\$ '
fi

# uname -r
2.4.0-test11

# sed '/C [lL]ibrary /!d; s/[^0-9]*\([0-9.]*\).*/\1/' /lib/libc.so.6
2.1.3

# mount|grep pts
none on /dev/pts type devpts (rw,gid=5,mode=640)

Any suggestions? Should this be addressed elsewhere? The reason I bring it
up here is because ALL ttys halt except those on the console.

-d

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