From owner-freebsd-hackers Mon Dec 28 15:06:26 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA08266 for freebsd-hackers-outgoing; Mon, 28 Dec 1998 15:06:26 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from dingo.cdrom.com (castles205.castles.com [208.214.165.205]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA08261 for ; Mon, 28 Dec 1998 15:06:24 -0800 (PST) (envelope-from mike@dingo.cdrom.com) Received: from dingo.cdrom.com (localhost [127.0.0.1]) by dingo.cdrom.com (8.9.1/8.8.8) with ESMTP id PAA13425; Mon, 28 Dec 1998 15:03:33 -0800 (PST) (envelope-from mike@dingo.cdrom.com) Message-Id: <199812282303.PAA13425@dingo.cdrom.com> X-Mailer: exmh version 2.0.2 2/24/98 To: zhihuizhang cc: hackers Subject: Re: Questions about interrupt handling In-reply-to: Your message of "Sat, 26 Dec 1998 23:24:54 EST." Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Mon, 28 Dec 1998 15:03:33 -0800 From: Mike Smith Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > I know that FreeBSD handles interrupts on a software basis which means > that we do not mask any interrupt off in 8259. I am just wondering if a > certain interrupt is masked off in 8259 or it does not get serviced quick > enough, what will the device controller (such as disk controller) respond? > Will it re-issue the interrupt or just give up? Or will it NOT generate > another interrupt until the previous one has been serviced? Maybe > different device controllers behave differently. Devices do tend to behave differently, but as a general rule no, a device will not generate another interrupt until the first has been serviced. Typical exceptions to this are vertical retrace and clock interrupts. This is why most decent device drivers also have a slow timeout routine which checks the hardware for status which would indicate a lost interrupt, and if found, calls the interrupt handler. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message