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Re: exception systems

   Your CMU/Mach bias is showing through...

I wish. I assure you that in my CMU days, the Mach guys had little interest
in the opinions of a wimp Scheme hacker who had never written a line of
kernel code.

   I think you are assuming that you need a full context switch when an
   interrupt arrives.  This is unnecessary, and the point of my previous

What you are proposing certainly provides a way to get very cheap
interrupts -- it is the way that Henry Massalin gets low-overhead
interrupts in Synthesis, for example.

But I don't like the semantics of thinking of it as an unplanned-for
subroutine call. It's really just that the interrupt handler is borrowing
the current thread's resources to execute for a little while. But I
think of that handler as another entity; this resource-stealing trick
is just an efficiency hack.

   One of the beauties of using Scheme for interrupt handling is that a
   closure is an incredibly effective mini-context.