[bde cc'd - it seems to be sio related]

I have an i386 toshiba laptop, running FreeBSD 5.0-CURRENT #4: Sat Aug 10
13:27:55 BST 2002. I can get a 100% reproducible hang by doing the

- Connect a serial cable between my laptop and a PC
- run "tip -9600 com1"
   (where com1 in /etc/remote is the default:
- power down the PC.

My laptop hangs solid, and DDB cannot be entered from the keyboard. Note
that if I close tip before powering down the PC, i don't get a hang. I am
not using ACPI.

Interestingly, if I type something and then power up the PC again, that
character will echo on the screen before locking up again. By
power-cycling the PC frequently, i could actually carry on using my
laptop. Power cycling the PC (either on->off or off->on) seems to unlock
the laptop for a fraction of a second.

I can also hold ctrl-alt-escape on my laptop, and power up or down the PC,
which will drop my laptop into DDB. From that point on, ddb works fine,
continuing back to userspace works fine, and my laptop is no longer hung.
Note however that often, from this point on until I quit tip, all
characters I send seem to be sent as uppercase.

Is it possible that the serial driver is getting confused, and the entry
into DDB is causing the hardware and/or some lock to be reset? Can I get
any other information to help diagnose this problem?

while in DDB during the hang, a show locks gives:
exclusive sleep mutex Giant r=0 (0xc0389d60) locked @ /usr/src/sys/kern/kern_intr.c:535
though I guess this is due to the keyboard event interrupt.

As this is 100% reproducible, i am able to test anything people want



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