From: Arjan van de Ven <arjanv@redhat.com>
To: Michael Frank <mhf@linuxmail.org>
Cc: "Randy.Dunlap" <rddunlap@osdl.org>,
"Grover, Andrew" <andrew.grover@intel.com>,
mgross@linux.co.intel.com, tim.bird@am.sony.com,
root@chaos.analogic.com, linux-kernel@vger.kernel.org
Subject: Re: Why no interrupt priorities?
Date: Sun, 29 Feb 2004 09:36:57 +0100 [thread overview]
Message-ID: <20040229083656.GB7264@devserv.devel.redhat.com> (raw)
In-Reply-To: <opr34h04mx4evsfm@smtp.pacific.net.th>
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On Sun, Feb 29, 2004 at 04:32:54PM +0800, Michael Frank wrote:
>
> Most interrupt controllers can read back IRQ's to see whether it is
> active. A shared IRQ would be readback active while any device
> connected to it desires service.
>
> x86 example for 8259A AT-PIC's Returns the state of IRQ0-15 in ax
> Note that jmp $+2 is only needed on some old 286/386 hardware
> to meet (real) 8259A cycle time requirements.
>
> - Intel syntax :)
>
> mov al,0ah
> out 0a0h,al
> jmp $+2
> in al,0a0h
> mov ah,al
> mov al,0ah
> jmp $+2
> out 20h,al
> jmp $+2
> in al,20h
interesting; however with modern cpus I suspect that a series of in/outs
like that is more expensive than one or two "surious" hardirq handler
calls...
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next prev parent reply other threads:[~2004-02-29 8:37 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-27 1:36 Why no interrupt priorities? Grover, Andrew
2004-02-27 3:02 ` Randy.Dunlap
2004-02-29 8:32 ` Michael Frank
2004-02-29 8:36 ` Arjan van de Ven [this message]
2004-02-29 9:52 ` Michael Frank
2004-02-27 5:32 ` Benjamin Herrenschmidt
2004-02-27 6:26 ` Michael Frank
2004-02-27 6:46 ` Benjamin Herrenschmidt
2004-02-27 9:05 ` Russell King
2004-02-27 13:31 ` Michael Frank
2004-02-27 13:45 ` Richard B. Johnson
2004-02-27 13:50 ` Russell King
2004-02-27 14:51 ` Michael Frank
2004-02-27 7:25 ` Arjan van de Ven
2004-02-27 10:15 ` Helge Hafting
2004-02-27 18:32 ` Mike Fedyk
-- strict thread matches above, loose matches on Subject: below --
2004-02-27 17:44 Grover, Andrew
2004-02-27 18:15 ` Chris Friesen
2004-02-27 18:42 ` Richard B. Johnson
2004-02-27 19:42 ` Michael Frank
2004-02-27 19:11 ` Michael Frank
2004-02-27 18:55 ` Matt Mackall
2004-02-27 19:09 ` Tim Hockin
2004-02-27 20:29 ` Matt Mackall
2004-02-27 19:19 ` Michael Frank
2004-02-27 20:53 ` Jesse Pollard
2004-02-29 9:43 ` Michael Frank
2004-03-01 16:57 ` Jesse Pollard
2004-03-01 17:35 ` Michael Frank
2004-03-02 15:25 ` Jesse Pollard
2004-02-27 11:37 Etienne Lorrain
2004-02-27 13:24 ` Michael Frank
[not found] <mailman.1077822002.21081.linux-kernel2news@redhat.com>
2004-02-27 8:00 ` Pete Zaitcev
2004-02-26 23:47 Albert Cahalan
2004-02-26 19:05 Tim Bird
2004-02-26 19:39 ` Richard B. Johnson
2004-02-26 21:02 ` Tim Bird
2004-02-26 21:30 ` Arjan van de Ven
2004-02-26 22:21 ` Mark Gross
2004-02-27 7:14 ` Arjan van de Ven
2004-02-27 11:27 ` Ingo Oeser
2004-02-27 11:52 ` Arjan van de Ven
2004-02-27 13:23 ` Richard B. Johnson
2004-02-27 12:04 ` Christoph Hellwig
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