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Re: exception systems
| Date: Thu, 18 Apr 1996 15:26:10 -0400
| From: Olin Shivers <shivers@lambda.ai.mit.edu>
| Cc: blume@cs.Princeton.EDU, will@ccs.neu.edu, rrrs-authors@mc.lcs.mit.edu
| Reply-To: shivers@ai.mit.edu
| 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.
That's only if you have a thread-oriented tasking model or program.
For some things it is the right thing. For others it is not.
Since it is easy and cheap to build such a threading model on top of
the low-overhead interrupt delivery mechanism, while it does not force
you to use that model, I don't see how implementing it that way at the
bottom level makes you think in any particular way at the higher
level.