UNIX-WIZARDS Digest V12#089

[Larry McVoy]

jfjr at mbunix.mitre.org writes:
>   My question: How are threads - light weight processes implemented
> without going into the kernel - I beleive ISIS does this

The short answer to your question is (I think) that all threads will block
when any of them enter the kernel & block.

The longer answer is that anyone can write the context switching code in
userland and allocate multiple stacks (I did this myself as a grad student
just for grins; fun but mostly useless because of the blocking).

There is some example code available on cs.arizona.edu in the sr subdir.
Pick up the tar file, unpack, and look in rts.
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Larry McVoy, Sun Microsystems     (415) 336-7627       ...!sun!lm or lm at sun.com