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From: lm@slovax.Eng.Sun.COM (Larry McVoy)
Newsgroups: comp.unix.wizards
Subject: Re: UNIX-WIZARDS Digest V12#089
Message-ID: <581@appserv.Eng.Sun.COM>
Date: 11 May 91 23:30:35 GMT
References: <26845@adm.brl.mil>
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Organization: Sun Microsystems, Mt. View, CA.
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jfjr@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.
---
Larry McVoy, Sun Microsystems     (415) 336-7627       ...!sun!lm or lm@sun.com