From owner-freebsd-hackers Thu Mar 30 17:23:38 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id RAA08145 for hackers-outgoing; Thu, 30 Mar 1995 17:23:38 -0800 Received: from Root.COM (implode.Root.COM [198.145.90.1]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id RAA08134 for ; Thu, 30 Mar 1995 17:23:34 -0800 Received: from corbin.Root.COM (corbin.Root.COM [198.145.90.18]) by Root.COM (8.6.8/8.6.5) with ESMTP id RAA15394; Thu, 30 Mar 1995 17:22:02 -0800 Received: from localhost (localhost [127.0.0.1]) by corbin.Root.COM (8.6.11/8.6.5) with SMTP id RAA00444; Thu, 30 Mar 1995 17:22:02 -0800 Message-Id: <199503310122.RAA00444@corbin.Root.COM> X-Authentication-Warning: corbin.Root.COM: Host localhost didn't use HELO protocol To: terry@cs.weber.edu (Terry Lambert) cc: vernick@cs.sunysb.edu, freebsd-hackers@FreeBSD.org Subject: Re: help with splbio, splnet, spl... In-reply-to: Your message of "Thu, 30 Mar 95 18:09:59 MST." <9503310110.AA29972@cs.weber.edu> From: David Greenman Reply-To: davidg@Root.COM Date: Thu, 30 Mar 1995 17:20:47 -0800 Sender: hackers-owner@FreeBSD.org Precedence: bulk >> >It's a tiered interrupt scheme. You can block all interrupts >> >at or below a specified priority while you are doing high >> >priority stuff so that it gets done in time. The "fast" >> >interrupts can't be blocked. >> >> It doesn't work this way in FreeBSD. It is not a tierd interrupt scheme. >> Each of the interrupt classes are independant and do NOT block the others. The >> only exception to this is tty and net are ored together if you are using SLIP >> or PPP (the reason should be obvious). > >This must be (relatively) new... If you consider 6 years old (when 386BSD was first being put together) as "new", well...I suppose. >Why isn't it tiered? Because it doesn't need to be. In fact, it is better if it isn't. >This conflicts with what you said about splclock() and splhigh() in >your previous post: > >] splhigh() and splclock() block all interrupts except "fast" interrupts. > > >Would it be more correct to say that it is partially tiered, with >the potential for multiple interrupt classes in a single tier not >interfering with each other? It would be more accurate to say that "fast" interrupts are a kludge and are escentially unblockable and don't fit into the spl* scheme at all. -DG