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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!spool.mu.edu!howland.reston.ans.net!gatech!news.mathworks.com!fu-berlin.de!irz401!orion.sax.de!uriah.heep!news From: j@uriah.heep.sax.de (J Wunsch) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: User PPP connection is s......l......o.......w......! Date: 19 Jul 1996 08:00:41 GMT Organization: Private BSD site, Dresden Lines: 27 Message-ID: <4snfb9$35r@uriah.heep.sax.de> References: <01bb6e37.014cfd20$38673fcb@simonh.addease.com.au> <4s1g7h$fr@anorak.coverform.lan> <4s3ul6$h0c@godzilla.zeta.org.au> <4scjps$92@anorak.coverform.lan> <4sfus4$meq@uriah.heep.sax.de> <4sj25l$k6@anorak.coverform.lan> Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) NNTP-Posting-Host: localhost.heep.sax.de Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Newsreader: knews 0.9.6 X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E brian@awfulhak.demon.co.uk (Brian Somers) wrote: > As I said, if the interrupt handler can get preempted - this is brilliant. > > I wondered if he *meant* calling something like preempt() (or whatever) > every now and again to allow higher priorities in. If interrupt > handlers can be preempted by higher level IPL routines (by swtch), > this implies (I think) that FreeBSD has to somehow lock any relevent > data structures (ones shared by interrupts of a different IPL) in a given > interrupt routine. Surely this is an overhead on a uniprocessor > machine.... 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. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)