6.2 SHOWSTOPPER - em completely unusable on 6.2

[Craig Boston]

On Fri, Sep 29, 2006 at 05:37:40PM -0400, Kris Kennaway wrote:
> and provide access to that file.
> 
> This will help to show whether something is causing Giant starvation.

http://www.gank.org/freebsd/stats.out

That's after about 25 seconds of the em0 interface being unable to
receive because of an apparent lack of interrupt processing (it can
still transmit though!  I had a half-open ssh session that continued to
receive data for a while).

Interesting data point #1: After a fresh boot, I'm unable to reproduce
the problem until I use the kernel linker.  After kldloading a module
(any module) and then immediately unloading it, my test case works 100%
until I reboot again.

Interesting data point #2: After a reboot, the problem moved from em0 on
irq19 to em1 on irq18.  I'm remote from the machine right now so I can't
test the usb controller that's sharing that interrupt, though I suspect
it experienced the same lack of response.

Craig