zio->io_cv deadlock

[Goran Lowkrantz]

--On February 12, 2009 5:07:43 +1100 Peter Jeremy 
<peterjeremy at optushome.com.au> wrote:

> On 2009-Feb-08 22:59:31 -0600, Kevin Day <toasty at dragondata.com> wrote:
>>
>> I'm playing with a -CURRENT install from a couple of weeks ago.
>> Everything  seems okay for a few days, then eventually every process
>> ends up stuck in  zio->io_cv. If I go to the console, it's responsive
>> until I try logging in,  then login is stuck in zio->io_cv as well.
>> Ctrl-Alt-Esc drops me into ddb,  but then ddb hangs instantly.
>
> I think I've seen this as well, though I can't be sure because X.org 7.4
> had trashed my console output.  Definitely, I could enter DDB but the
> crashdump I requested (blind) never appeared.  I don't believe I was
> doing anything unusual (other than trying to use X.org 7.4).
>
I see this now and then in single-user mode during make installworld, 
ezjail-admin update -i or in multi-user when building a system in the 
background and updating ports at the same time.

I have an USB keyboard and have not been able to break into the debugger 
with that, have legacy mode enabled in the bios (award).

Anyone know how to send break from USB tgb?

/glz