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Date:      Mon, 27 Mar 2000 10:55:57 -0700 (MST)
From:      Nate Williams <nate@yogotech.com>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        Nate Williams <nate@yogotech.com>, Daniel Eischen <eischen@vigrid.com>, nms@otdel-1.org, freebsd-current@FreeBSD.ORG
Subject:   Re: Is there spinlocks/semaphores available for drivers?
Message-ID:  <200003271755.KAA26648@nomad.yogotech.com>
In-Reply-To: <200003271753.JAA41782@apollo.backplane.com>
References:  <Pine.SUN.3.91.1000327072156.16642A-100000@pcnet1.pcnet.com> <200003271731.JAA41585@apollo.backplane.com> <200003271746.KAA26582@nomad.yogotech.com> <200003271753.JAA41782@apollo.backplane.com>

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> :> :>     *not* preempted except when being interrupted, so there are no
> :> :>     'priorities', per say.  Or, rather, the relative priority is strictly
> :> :>     that the interrupt takes priority over supervisor code except when
> :> :>     disabled by said supervisor code.
> :> :
> :> :But locks with owners wouldn't have to disable interrupts (given that
> :> :we have interrupt threads).  What about shared interrupts?  You could
> :> :still field and process the interrupt as long as it was for a different
> :> :device.
> :> :Dan Eischen
> :> 
> :>     The word 'too bad' comes to mind re: shared interrupts.
> :
> :Too bad is not acceptable.  If we want to support multi-function
> :PCMCIA/CardBus cards, we *must* do shared interrupts, and multi-function
> :cards are becoming the standard, rather than the exception.
> :
> :Nate
> 
>     First, each PCI slot has *two* assignable interrupts.
> 
>     Second, CardBus cards are so slow that you would see absolutely no
>     gain in performance whatsoever by being able to run concurrent interrupt
>     threads for a single shared interrupt.

Huh?  CardBus cards are *not* slow.  PCMCIA cards are, but CardBus is
pretty dang fast.



Nate


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