Re: Mark Russinovich's reponse Was: [OT] Comments to WinNT Mag !! (fwd)

Derek Fawcus (derek@spider.com)
Wed, 5 May 1999 11:49:52 +0100

On Wed, May 05, 1999 at 08:37:33AM +1000, Richard Gooch wrote:
> Mark H. Wood writes:
> >
> > Ugh. I liked the VMS model here. When you queue an I/O request,
> > one of the things you can attach to it is the address of a
> > procedure. When the request completes, the kernel creates a
> > temporary thread to execute the I/O rundown code, and part of that
> > rundown is to call the procedure you supplied.

> What was the cost of creating the "temporary thread"? Anyway, we can
> do much the same thing with signals, except we don't need to create a
> temporary thread.

If they're anything like the similar model I used with FlexOS
(aka CDOS) then the 'temporary thread' was actually more like a
signal handler.

In FlexOS these things (called SWI's) would interrupt the main line
of execution in the process, but only one could be active at a time.

DF

-- 
Derek Fawcus                                                    derek@spider.com
Spider Software Ltd.                                        +44 (0) 131 475 7034


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