Subject: Re: Lightweight processes
To: Neil <Carson@rmcs.cranfield.ac.uk>
From: Chris G. Demetriou <cgd@CS.cmu.edu>
Date: 02/10/1997 12:07:44
> Just been reading that apparently in 4.4BSD there was some support for
> what they termed 'lightweight processes' --- effectively threads but each
> one with a different process ID --- in the kernel, but they were never used
> due to a lack of a suitable C library.
Uh, I'd like to know who said that.
There exists support in the kernel for kernel-only "processes"
(e.g. the swapper and pagedaemon, and nfs I/O daemons). However,
this is not and never was a general-purpose facility, nor has there
ever been any such general-purpose facility in 'vanilla' BSD kernels
that i'm aware of.
If somebody's claiming that there is such a general purpose facility
in 4.4BSD, they are either incorrect, "optimistic," or you're
misinterpreting what they're saying. I say "optimistic" because some
books, e.g. the "Design and Implementation of the 4.?BSD... System",
tend to describe features or aspects of the system ... in rosy terms,
where no such features exist or where they don't nearly live up to the
description they're given.