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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!nntp.coast.net!dispatch.news.demon.net!demon!awfulhak.demon.co.uk!awfulhak.demon.co.uk!awfulhak.demon.co.uk!not-for-mail From: brian@awfulhak.demon.co.uk (Brian Somers) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: User PPP connection is s......l......o.......w......! Date: 20 Jul 1996 05:25:04 +0100 Organization: Coverform Ltd. Lines: 23 Message-ID: <4spn30$2ds@anorak.coverform.lan> References: <01bb6e37.014cfd20$38673fcb@simonh.addease.com.au> <4snfb9$35r@uriah.heep.sax.de> NNTP-Posting-Host: localhost.coverform.lan X-NNTP-Posting-Host: awfulhak.demon.co.uk X-Newsreader: TIN [version 1.2 PL2] J Wunsch (j@uriah.heep.sax.de) wrote: : They are not being preempted by swtch(), this one is only appropriate : for process context switches. (Actually, what Vahalia describes as : swtch() is mi_switch() in BSD, which in turn calls cpu_switch().) : Interrupt handlers of the same priority cannot be preempted, but other : SPLs are always treated as ``higher priority'', i.e. the various SPLs : are mutually independant. I haven't looked into what might be locked : inside the generic interrupt code. Ah, I misunderstood your use of preempt.... Here, the interrupt handler is just getting interrupted by a higher priority interrupt (and the handler for that is being run). As I understand it, this is not a problem as far as mucking around with data structures is concerned. You've got a situation where *only* higher priority interrupts get run "inside" the running of the first interrupt handler. You'll never get a situation where mi_switch() sticks its head in and puts a kernel-mode process in front of the interrupt handler..... Now *that* would be a pig to code ! -- Brian <brian@awfulhak.demon.co.uk> Don't _EVER_ lose your sense of humour....