Date: Mon, 28 Apr 1997 07:59:35 -0400 (EDT) From: Chuck Robey <chuckr@mat.net> To: Ben Black <black@zen.cypher.net> Cc: FreeBSD-SMP@FreeBSD.org Subject: Re: SMP Message-ID: <Pine.BSF.3.91.970428075918.24289E-100000@Journey2.mat.net> In-Reply-To: <Pine.LNX.3.91.970428014800.32065R-100000@zen.cypher.net>
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On Mon, 28 Apr 1997, Ben Black wrote: > > > > 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? > > > > hence my saying one kernel. there is a single kernel image in memory and > both CPUs execute different (or the same) parts of it at the same time. > the single lock is to keep the CPUs from stepping on each other. when > one CPU wants to access a shared resource (and pretty much everything in > the kernel is considered shared) then it acquires the mplock, does its > business, releases the lock and continues. if the other CPU has the lock > when one wants to acquire it, the second CPU waits. > > one kernel, one lock. Ahh, ok, I'm clear on that now. > > > b3n > > > ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@eng.umd.edu | communications topic, C programming, and Unix. 9120 Edmonston Ct #302 | Greenbelt, MD 20770 | I run Journey2 and picnic, both FreeBSD (301) 220-2114 | version 3.0 current -- and great FUN! ----------------------------+-----------------------------------------------
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