Date: Fri, 22 Jun 2001 07:01:03 -0500 From: Mike Meyer <mwm@mired.org> To: j mckitrick <jcm@FreeBSD-uk.eu.org> Cc: Michael Lucas <mwlucas@blackhelicopters.org>, Dag-Erling Smorgrav <des@ofug.org>, freebsd-chat@FreeBSD.ORG Subject: Re: most complex code in BSD? Message-ID: <15155.13183.377957.392221@guru.mired.org> In-Reply-To: <20010622114548.A51977@dogma.freebsd-uk.eu.org> References: <20010621233210.A37804@dogma.freebsd-uk.eu.org> <xzp7ky5e4ua.fsf@flood.ping.uio.no> <20010622062238.A45123@blackhelicopters.org> <20010622114548.A51977@dogma.freebsd-uk.eu.org>
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j mckitrick <jcm@FreeBSD-uk.eu.org> types: > On Fri, Jun 22, 2001 at 06:22:38AM -0400, Michael Lucas wrote: > | When I took the two-day FreeBSD Internals course McKusick taught, he > | brought up the context-switching code. > | > | The original UNIX authors were not much on comments. When they put a > | comment, it was to explain something really, really, *really* difficult. > | > | Apparently there was a seven-word comment in the context switching > | code that gave him a bit of a start: "You are not expected to > | understand this." Don't know if it's still there, but it's still > | probably pretty scary. > > Is this supposed to be in C or asm? I thought context switches were among > the only asm/machine dependent code. For the v6 kernel, this is in C code. I never went looking for it in later code, so I don't know when it vanished. The comment in question is a couple of paragraphs, followed by that seven-word note. If I remember correctly - my copy of Lyons being in storage - the code was the context-switching code, and what was being explained was the mechanism that was used to start the first process, which involved very machine-dependent work so that that code would do the job. Since it's been a decade or two since I looked at that code, I may not remember correctly. <mike -- Mike Meyer <mwm@mired.org> http://www.mired.org/home/mwm/ Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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