In message <Pine.SGI.3.91.970103171827.6145L-100000@physig4.ph.kcl.ac.uk>
          Mark Brinicombe <amb@physig.ph.kcl.ac.uk> wrote:

>   Ok the ibuf overflow problem has been fixed ;-)

Great!

> Suddenly you have two parts of the serial driver playing with the input
> buffers at the same time ;-)
> 
> Anyway this problem is fixed by making sure that soft interrupts are only 
> ever delivered when the last nested interrupt is finished. (2 lines of 
> code to fix ;-)

How do you spot something like this?
Do you have advanced diagnostic methods at hand or is the only way to find
something like this to work through the relevant part of the code?

> Sorry for the time it took to fix this one. I really should have sat down 
> and looked into it earlier.

Well, I have mentioned sometime that this has shown up after you have enhanced
the interrupt code.
But there's nobody to blame for not working out that two interrupts were
playing on the buffer at the same time.
I know that, after you've found it you bang your head because it was all so
obvious - apparently.

Markus