Problem with iterative load/unload of em

[Jack Vogel]

Our internal test group has run into a problem, I have witnessed it,
but not had time to pursue it. I was wondering if this has been
previously observed, and if anyone has any thoughts.

What they do is run a script that runs 100 passes at loading,
bringing up and configuring the driver, then bringing down and
unloading. It does this as fast as the script will run.

At some random point in the loop it will cause a crash, I do
not have a stack trace in front of me now to include. I am
pretty sure the stack varies from instance to instance.

This has been observed on both Intel versions of the em driver
and community based versions, and both on 5.4, 6.0, and 6.1.

If sleeps are inserted into the script the problem will not
happen, so its timing sensitive.

Its sort of an artificial test, but this apparently didnt happen
on 4.11, also reported to not happen with a Broadcom.

I've looked at the detach path and so far nothing real
obvious jumps out at me. I am too busy to look at this
right now, but any ideas or suggestions are welcome.

Jack