From owner-freebsd-smp Mon Apr 28 10:45:43 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id KAA27213 for smp-outgoing; Mon, 28 Apr 1997 10:45:43 -0700 (PDT) Received: from phaeton.artisoft.com (phaeton.Artisoft.COM [198.17.250.50]) by hub.freebsd.org (8.8.5/8.8.5) with SMTP id KAA27208 for ; Mon, 28 Apr 1997 10:45:40 -0700 (PDT) Received: (from terry@localhost) by phaeton.artisoft.com (8.6.11/8.6.9) id KAA02167; Mon, 28 Apr 1997 10:44:21 -0700 From: Terry Lambert Message-Id: <199704281744.KAA02167@phaeton.artisoft.com> Subject: Re: SMP To: chuckr@mat.net (Chuck Robey) Date: Mon, 28 Apr 1997 10:44:21 -0700 (MST) Cc: black@zen.cypher.net, FreeBSD-SMP@FreeBSD.org In-Reply-To: from "Chuck Robey" at Apr 27, 97 11:58:37 pm X-Mailer: ELM [version 2.4 PL24] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-smp@FreeBSD.org X-Loop: FreeBSD.org Precedence: bulk > I'm confused, then. If there's only one kernel, then only one cpu can > run it, so only one cpu can field the system calls. If both cpu's can > field system calls, then unless they contact the other one to get the > work done, then there must be two copies of the kernel ruinning, right? > > I'm probably misunderstanding something. Maybe you meant only one piece > of software called "kernel" but two cpus running it? The lock is acquired at system call time. Only one CPU can acquire the lock at a time, so the kernel is not reentered. But any CPU may acquire the lock. Effectively, there is a single kernel which can be run by only one CPU at a time. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.