From owner-freebsd-questions@FreeBSD.ORG Fri Jul 21 20:54:14 2006 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E955516A4DD for ; Fri, 21 Jul 2006 20:54:14 +0000 (UTC) (envelope-from derek@computinginnovations.com) Received: from betty.computinginnovations.com (dsl081-142-072.chi1.dsl.speakeasy.net [64.81.142.72]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4841A43D45 for ; Fri, 21 Jul 2006 20:54:10 +0000 (GMT) (envelope-from derek@computinginnovations.com) Received: from p17.computinginnovations.com (dhcp-10-20-30-100.computinginnovations.com [10.20.30.100]) (authenticated bits=0) by betty.computinginnovations.com (8.13.6/8.12.11) with ESMTP id k6LKrpjZ041625; Fri, 21 Jul 2006 15:53:52 -0500 (CDT) Message-Id: <6.0.0.22.2.20060721155056.025578d8@mail.computinginnovations.com> X-Sender: derek@mail.computinginnovations.com X-Mailer: QUALCOMM Windows Eudora Version 6.0.0.22 Date: Fri, 21 Jul 2006 15:53:41 -0500 To: Jamie , freebsd-questions@freebsd.org From: Derek Ragona In-Reply-To: <20060721145851.I95847@floyd.gnulife.org> References: <20060721145851.I95847@floyd.gnulife.org> Mime-Version: 1.0 X-ComputingInnovations-MailScanner-Information: Please contact the ISP for more information X-ComputingInnovations-MailScanner: Found to be clean X-ComputingInnovations-MailScanner-From: derek@computinginnovations.com X-Spam-Status: No Content-Type: text/plain; charset="us-ascii"; format=flowed X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: Subject: Re: traps and interrupts X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 Jul 2006 20:54:15 -0000 Traps go along with signal handlers. You should do a man on signal for more information. The interrupts you are referring to are at a device driver level, where a driver interacts directly with the hardware. -Derek At 03:21 PM 7/21/2006, Jamie wrote: > I'm going through "Design and Implementation of the FreeBSD operating >system" (McKusick) right now, and I've got some questions... > > > >1) The book refers to software traps... > >(page 51 para 2): > >" Software initiated traps are used by the syste mto force the scheduling >of an event, such as process rescheduling or network processing, as soon >as possible. Software initiated traps are implemented by setting a flag >that is checked whenever a process is preparing to exit from the kernel. >If the flag is set, the software interrupt code is run instead of exiting >from the kernel." > > > Unfortunately, the book doesn't give any examples of how this is >implemented in enough detail for me to understand. The only example it >seems to really give of a software interrupt is the process that delivers >the incoming packets to their destination processes. (??) > > I was trying to learn more about how the trap function is implemented, >so I read up on hardware traps in my IA-32 system manual (the one Intel >ships out for free if you ask them for it). > > That manual says that there is basically a set of INT calls you can make >that are in an IDT table. Some of these are hard wired, like 0-19, if I >recall. Then 33-255 are all software definable. > > I am guessing that these high priority software interrupt routines are >stored at locations pointed to by elements 33-255 in the IDT table. Is >that correct? Or, do these software interrupt processes have no need to >trap into the routines in the IDT? > > > I hope this question makes sense...I'm just trying to get a more lucid >understanding of how "software interrupts" or "software traps" as they're >referred to in this text, are implemented. > > > > - Jamie > > > > > > > >The Moon is Waning Crescent (12% of Full) >_______________________________________________ >freebsd-questions@freebsd.org mailing list >http://lists.freebsd.org/mailman/listinfo/freebsd-questions >To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" > >-- >This message has been scanned for viruses and >dangerous content by MailScanner, and is >believed to be clean. >MailScanner thanks transtec Computers for their support. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. MailScanner thanks transtec Computers for their support.