Stefano Barbato wrote:
> Dual PIII
> kernel 2.4.21-rc2 (w/ SMP)  (2.5.69 below)
> ...
>
> I put a few printk before the BUG() and I found that the offending if() is
> this:
>         if(qh->qh_state != QH_STATE_LINKED
>                                 && qh->qh_state != QH_STATE_UNLINK_WAIT)
>
> because qh_state were QH_STATE_COMPLETING.

I got a similar SMP report recently, but without info about
which clause was failing -- which is a key clue, thanks!!

The COMPLETING state is used only while a QH is being
scanned for completed TDs.  (Think CPU-0 irq handler.)
Looking at the handful of places that call the routine
reporting the BUG(), a couple seem like they could make
trouble with multiple CPUs in the driver.