From owner-freebsd-current@FreeBSD.ORG  Mon Apr 11 06:58:02 2005
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id B297A16A4D4
	for <freebsd-current@freebsd.org>;
	Mon, 11 Apr 2005 06:58:02 +0000 (GMT)
Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 80E3943D45
	for <freebsd-current@freebsd.org>;
	Mon, 11 Apr 2005 06:58:02 +0000 (GMT)
	(envelope-from dillon@apollo.backplane.com)
Received: from apollo.backplane.com (localhost [127.0.0.1])
	j3B6w20e048553;	Sun, 10 Apr 2005 23:58:02 -0700 (PDT)
	(envelope-from dillon@apollo.backplane.com)
Received: (from dillon@localhost)
	by apollo.backplane.com (8.12.9p2/8.12.9/Submit) id j3B6w2nb048552;
	Sun, 10 Apr 2005 23:58:02 -0700 (PDT)
	(envelope-from dillon)
Date: Sun, 10 Apr 2005 23:58:02 -0700 (PDT)
From: Matthew Dillon <dillon@apollo.backplane.com>
Message-Id: <200504110658.j3B6w2nb048552@apollo.backplane.com>
To: Scott Long <scottl@samsco.org>,
	Doug White <dwhite@gumbysoft.com>, freebsd-current@freebsd.org
References: <20050406233405.O47071@carver.gumbysoft.com>
	<200504081656.51917.jhb@FreeBSD.org>
	<20050410152946.W82708@carver.gumbysoft.com>
	<20050410172818.D82708@carver.gumbysoft.com>
	<200504110231.j3B2VOYr047361@apollo.backplane.com> <425A10DD.70500@samsco.org>
	
Subject: Re: Potential source of interrupt aliasing
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 11 Apr 2005 06:58:02 -0000

    Hmm.  I can think of two solutions that avoid masking:

    * Change the trigger mode from level to edge as a means of masking the
      interrupt, then change it back to level triggered to unmask.  This
      would be done in the IO APIC.

    * Change the delivery mode to low-priority for the interrupt that occured
      and use the priority field to mask the interrupt to the cpu.  This
      would be done in the IO APIC with the LAPIC's TPR set appropriately.

    These are off-the-cuff ideas.  I don't know how easy or hard it would be
    to implement (yet).  But, certainly, changing the trigger mode can't be
    any more complicated then messing around with the mask.

							-Matt