> This would explain processes that are stuck in 'D' state.  Imagine that such
> a process has requested some I/O that requires a flush to disk.  The top 
> half of the driver enters the write request into the queue and waits for the
> request to be serviced before returning to the user process.  Normally 
> the esp chip will interrupt once the request is done, which is the signal 
> that the kernel uses to return to the user process.  However if this 
> interrupt is ackowledged inadvertantly by one of these spurrious reads, 
> it will be lost and the requesting process will hang forever.


A watchdog timer is started in the esp driver for every transaction with
the scsi engine. A missed interrupt would result in "esp(..): timeout"
console messages. Both the esp chip and the scsi bus get reset after
and the MI scsi system will eventually retry the entire operation.

-pk