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Xref: sserve comp.os.386bsd.misc:3062 comp.os.linux.misc:21221 Newsgroups: comp.os.386bsd.misc,comp.os.linux.misc Path: sserve!newshost.anu.edu.au!munnari.oz.au!spool.mu.edu!howland.reston.ans.net!usc!elroy.jpl.nasa.gov!decwrl!netcomsv!calcite!vjs From: vjs@calcite.rhyolite.com (Vernon Schryver) Subject: Re: Usefulness of BSD/Linux Source Knowledge (was BSD vs. LINUX) Message-ID: <Cu478w.7pq@calcite.rhyolite.com> Organization: Rhyolite Software Date: Sat, 6 Aug 1994 13:10:08 GMT References: <31mfon$efs@glitnir.ifi.uio.no> <31racs$si2@nyheter.chalmers.se> <Cu2ny3.J9o@boulder.parcplace.com> Lines: 28 In article <Cu2ny3.J9o@boulder.parcplace.com> imp@boulder.parcplace.com (Warner Losh) writes: >In article <31racs$si2@nyheter.chalmers.se> tl@cd.chalmers.se >(Torbj|rn Lindgren) writes: >>Adding SMP was prrobably rather easy. Just put a big lock on the whole >>kernel... This means that only one process (or thread) can be in the >>kernel in the kernel a given time, but if that process can run on any >>processor you have a SMP (per definition, symmetric means that either >>processor may run kernel tasks, not that more than one process may be >>in the kernel). > >What you describe is ASMP. With ASMP, you must block until the >"Master" CPU is ready to process your kernel request, where with you >suggestion, you must wait for the current CPU to finish being in the >kernel. It sounds like you have a floating Master CPU. A SMP kernel, >btw, means that you can have multiple processes in the kernel >concurrently and not more than one of them is accessing the same >criticial structures at the same time. So one could be servicing a >serial line interrupt while the other one is blitting stuff to a >remote X server. I think that's wrong, that it is a Symmetric MultiProcessing system, albeit with rather coarse locking. It certainly is not Master/Slave. Dividing the simplest, single mutual exclusion region scheme in two would be trivial (say by catagorizing system calls), but would not change it's fundamental nature. Vernon Schryver vjs@rhyolite.com