Strange semi-hangs on 5.4

[Eirik Øverby]

Hi all,

With relatively recent 5.4, I'm seeing hangs that worry me. The box  
(dual opteron) accepts keyboard input, but it won't actually DO  
anything.. SSHing in gives me a TCP session but no actualy password  
prompt. Trying to log in on (serial) console doesn't work, I just get  
a newline after entering the username, no password prompt. On SSH  
shells alredy open, I can't even get a new prompt line, all I get is  
newlines.

But the best part is: The kernel debugger doesn't seem to work. I've  
got BREAK_TO_DEBUGGER in my kernel config, but here's what happens:

telnet> send brk
KDB: enter: Line break on console
3KtDhB:a s tpaicdk  1b1a0e00:0
aitd l e _ p r o c ( )   a t   i d l e _ p r o c + 0 x 1 1 3
m???b >   o|?|??f?tpie  rat0f :          n o p
     dd
db>
db>
db
d
d
dd
db>
db
dd
db>
db
d
db>
dd

...and then it keeps spewing d's and db's and stuff at me at  
whichever speed my serial can handle. In other words, useless. All I  
can do at this point is log in to my power switch and powercycle the  
box.

Anyone?

/Eirik