link state changes take a "long" time to execute

[Robert Watson]

I'm running with task queue instrumentation on my notebook, and generate 
warnings when task queues take more than 1/10th of a second to execute. 
Normally the warnings fire only during the boot when tasks start being 
scheduled by ACPI, but the ACPI task queue thread isn't yet being 
scheduled to run because the scheduler hasn't been kicked off yet.  I saw 
one this afternoon as follows:

taskqueue_run: warning, queue time of 0.133978201 for context 0xc0687c90

On my kernel, this function pointer resolves to:

c0687c90 t do_link_state_change

So it sounds like there's a substantial delay in the link change thread -- 
probably because another task takes a long time to execute, maybe 
blocking or delaying the task thread and preventing another task from 
running.  On this box, I'm running with an idle if_xl, and an in-use 
if_wi, which probably went into the associated state about when the 
message was printed.  Kernel source date is June 3.

Robert N M Watson