Date: Mon, 25 Nov 1996 22:29:55 +0800 From: Peter Wemm <peter@spinner.dialix.com> To: Barney Wolff <barney@databus.com> Cc: freebsd-smp@freebsd.org Subject: Re: Thread issues Message-ID: <199611251429.WAA01541@spinner.DIALix.COM> In-Reply-To: Your message of "Mon, 25 Nov 1996 08:18:00 EST." <32999eda0.5633@databus.databus.com>
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Barney Wolff wrote:
> The only reason I can conceive of to depart from standard APIs is if
> they are seriously broken, and I've seen no such claim. As long as
> the Posix thread API is available, having it built on some more
> comfortable underlying proprietary API is fine - Unixware does it
> that way. But not to have the Posix API available would condemn
> fbsd-smp to irrelevancy.
FreeBSD already has posix threads, BTW. The challenge is to produce
a simple "back end" API for the thread library to work on multiple
cpus at once. I think it would be a mistake to move the posix thread
API into the kernel...
> Of course, a great deal of the real work comes in making thread-safe
> versions of the C library, where possible. Debate over APIs just
> adds delay - which is a good reason to go with the standard.
We already have a thread-safe C library.. (see libc_r)
What we are missing:
1: the ability to do blocking IO within threads. I wrote 95% of the code
to support this, but never got around to finishing it due to some
sticky efficiency problems with context switching in the kernel.
2: the ability to have one program's threads execute on multiple cpus at
once. This becomes "easy" once #1 is done.
3: a synchronisation back end. We may not need kernel support for this
if we use kernel-style locked bus cycle mutex operations in user mode.
I was working on part 1 for the non-smp kernel, since it was applicable to
both the normal and the smp kernel. I have learned enough over the last
few months to finish this now. Part 2 is merely an extension of part 1.
Cheers,
-Peter
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