Processes stuck in *unp_m after recent uipc changes

[Robert Watson]

On Tue, 27 Feb 2007, Robert Watson wrote:

> On Tue, 27 Feb 2007, Jiawei Ye wrote:
>
>> With the latest uipc locking changes, I experienced a hard lockup on my 
>> -current machine. Many processes got stuck in *unp_m state and 
>> ctrl-alt-delete at the console cannot properly restart the machine and I 
>> had to hard-reset (no coredump available). Is there anyway to diagnose 
>> this?
>
> Please configure WITNESS, DDB, and BREAK_TO_DEBUGGER on a box with a serial 
> console.  Then attach the output of "ps", "show alllocks", and "alltrace" to 
> an e-mail.  With any luck, this is a leaked lock in some missed error case 
> and we can just add a missing unlock.  Thanks!

Obviously, INVARIANTS also good on general principle. :-)

See the handbook chapter on debugging, and in particular live DDB debugging, 
if you're running into any problems.

Robert N M Watson
Computer Laboratory
University of Cambridge