Date: Thu, 30 Mar 95 18:17:01 MST From: terry@cs.weber.edu (Terry Lambert) To: davidg@Root.COM Cc: nate@trout.sri.mt.net, freebsd-hackers@FreeBSD.org Subject: Re: help with splbio, splnet, spl... Message-ID: <9503310117.AA00103@cs.weber.edu> In-Reply-To: <199503310046.QAA00377@corbin.Root.COM> from "David Greenman" at Mar 30, 95 04:46:17 pm
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> Interrupts are blocked via software in FreeBSD - the interrupt controller > isn't messed with (the interrupts are always enabled). I think you're > confusing its arbitration priority with the classic unix spl "tiering" that > Terry thought we had. When presented with multiple simultaneous interrupts, > the interrupt controller does have an arbitration priority scheme that is > based on the interrupt number...but this nothing to do with spl tiering. Unless the splbio/splclock blocking of everything else but fast wasn't true, it's at least partiall tiered (jury still out on that, since you haven't had time to reply to the posting I made immediately before this one). If this is truly the case, then it's a major step forward toward kernel preemption (depending on implementation, I suppose). The question I then have is why is it still called "spl" which stands for "set priority level" if what it is really doing is blocking a particular class of interrupts instead of all interrupts at or below a particular level? A duck us like a bicycle because they both have two wheels except the duck. 8-). Terry Lambert terry@cs.weber.edu --- Any opinions in this posting are my own and not those of my present or previous employers.
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