Date: Thu, 30 Mar 1995 16:46:17 -0800 From: David Greenman <davidg@Root.COM> To: Nate Williams <nate@trout.sri.mt.net> Cc: terry@cs.weber.edu (Terry Lambert), freebsd-hackers@FreeBSD.org Subject: Re: help with splbio, splnet, spl... Message-ID: <199503310046.QAA00377@corbin.Root.COM> In-Reply-To: Your message of "Thu, 30 Mar 95 17:45:05 MST." <199503310045.RAA08865@trout.sri.MT.net>
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>> It doesn't work this way in FreeBSD. It is not a tierd interrupt scheme. >> Each of the interrupt classes are independant and do NOT block the others. The >> only exception to this is tty and net are ored together if you are using SLIP >> or PPP (the reason should be obvious). > >Interesting. I wasn't aware that you could do this on a PC, since I was >under the impression that you had to have a tiered scheme with the 8259. >Obviously I was mis-informed since this would imply that no interrupt is >given a higher priority over another interrupt. Is there any way this >can be done short of OR'ing a lot of the different masks together to >keep certain interrupts from happening? Is this how the sio driver does >things? 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. -DG
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