From owner-cvs-sys  Mon Jul 28 05:13:13 1997
Return-Path: <owner-cvs-sys>
Received: (from root@localhost)
          by hub.freebsd.org (8.8.5/8.8.5) id FAA28404
          for cvs-sys-outgoing; Mon, 28 Jul 1997 05:13:13 -0700 (PDT)
Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.19])
          by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id FAA28137;
          Mon, 28 Jul 1997 05:11:54 -0700 (PDT)
Received: (from bde@localhost) by godzilla.zeta.org.au (8.8.5/8.6.9) id WAA15768; Mon, 28 Jul 1997 22:07:00 +1000
Date: Mon, 28 Jul 1997 22:07:00 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199707281207.WAA15768@godzilla.zeta.org.au>
To: bde@zeta.org.au, msmith@atrad.adelaide.edu.au
Subject: Re: cvs commit: src/sys/i386/isa isa.c
Cc: cvs-all@FreeBSD.ORG, cvs-committers@FreeBSD.ORG, cvs-sys@FreeBSD.ORG,
        msmith@FreeBSD.ORG
Sender: owner-cvs-sys@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

>> Erm, it already used splhigh() to ensure this.
>
>Does splhigh() prevent fast interrupt handlers from being called?  The

No.

>> Rule 1: No function can be called safely with CPU interrupts disabled.
>
>Can you explain "why" in simple terms?

Because CPU interrupts should not be masked for long.  Keeping calls
short puts too much of a burden on the callee.  Some caller (unknown
to the callee) may be depending on the callee to take <= N usec.  A
minor algorithm change may invalidate this.

Bruce