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Date:      Thu, 5 Dec 1996 13:01:17 -0700 (MST)
From:      Terry Lambert <terry@lambert.org>
To:        smp@csn.net (Steve Passe)
Cc:        terry@lambert.org, ccsanady@friley216.res.iastate.edu, peter@spinner.dialix.com, smp@freebsd.org
Subject:   Re: make locking more generic?
Message-ID:  <199612052001.NAA19785@phaeton.artisoft.com>
In-Reply-To: <199612051940.MAA14434@clem.systemsix.com> from "Steve Passe" at Dec 5, 96 12:40:55 pm

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> >If CPU 1 is servicing INT 12 from a disk controller, and you get INT 4
> >from a serial port, don't you *want* CPU 2 to service the INT 4 in
> >parallel???
> 
> yes, you do.  but the problem is that CPU 1 holds the lock, so if CPU2
> tries to service INT 4, it starts spinning in the un-obtainable lock till CPU1
> finishes servicing INT 12.  At this point CPU1 releases the lock, CPU2
> finally gets it and can proceed to service INT 4. Might as well let CPU2
> alone to do whatever it is doing instead.  If the INT 4 is of higher priority
> than INT 12, CPU1 could start servicing it immediatly.
> 
> The proper form of fine-grainularity could eliminate this problem.

Ah.  I see.  We are still talking about the global kernel entrancy lock
in this case.  Never mind then (the global entrancy lock is bogus).


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.




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