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Date:      Tue, 11 Apr 2000 09:59:00 -0700 (PDT)
From:      Matthew Jacob <mjacob@feral.com>
To:        Terry Lambert <tlambert@primenet.com>
Cc:        arch@freebsd.org
Subject:   Re: BUF/BIO roadmap.
Message-ID:  <Pine.BSF.4.05.10004110952590.60516-100000@semuta.feral.com>
In-Reply-To: <200004111649.JAA17290@usr01.primenet.com>

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> 
> It also seems to me that kernel threads are _still_ a significantly
> bad idea, since the problems faced in kernel preemption are a subset
> of the problems faced in Real Time support, and that as a result, it
> will be significantly harder to support Hard Real Time in the future
> without significant revisions of the the OS architecture.

Whether it's threads or additional kernel processes that can be schedule from 
interrupt level, I don't care, but the class of problems this solves for me
makes it very desirable. The current approach in Linux of creating an
interrupt/error handler thread per SCSI host adapter is *very* cool with
respect to solving complex error issues in a clean fashion. The existing CAM
subsystem would be a *lot* easier to follow/debug if it were threads/proc
based.

From a political point of view it's important as well. Veritas points out to
me that they'll be porting VxFS and other products to Linux long before they'd
port it to FreeBSD because Linux (like Solaris, NT, HP/UX) have a kernel
threads model. You may be right with what you assert- I won't attempt to
involve myself at that level, but from the point of view of this platform
succeeding, well, I believe you're lifting at the heavy end, my friend.

-matt







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