Date: Mon, 7 Aug 2000 19:38:07 -0700 (PDT) From: John Polstra <jdp@polstra.com> To: current@freebsd.org Cc: dg@root.com Subject: Re: Ugly, slow shutdown Message-ID: <200008080238.TAA40871@vashon.polstra.com> In-Reply-To: <200008080135.SAA04815@implode.root.com> References: <200008080135.SAA04815@implode.root.com>
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In article <200008080135.SAA04815@implode.root.com>, David Greenman <dg@root.com> wrote: > >I will add that this is the pattern that Kirk teaches in his kernel > >internals class. > > If that's true, Do you want me to fax you a copy of page 15 of his class notes from the course he gave at last year's FreeBSDCon, or will you just take my word for it? > then he should practice what he preaches. Some of the code that I'm > refering to (e.g. lockf) was apparantly written by him. Whether Kirk practices what he preaches is irrelevant to this discussion. Instead of focusing on a 1-sentence "I will add ..." from my posting, why not respond to the main thrust of it -- the paragraph I quoted from the Birrell paper? > I'll say again, however, that some of the cases that rely on the > historical symantics would become very expensive if they had to go > through a series of complex checks (perhaps list traversals, etc), > in order to verify that the wakeup wasn't bogus. I personally don't > think this is an improvement. Some of them might be expensive, but most of them would not. Obviously the waker-upper knows that the condition is true. Otherwise the existing code which doesn't check wouldn't work. In the expensive cases the waker-upper could simply set a flag for the sleeper to check. Note, I am not expressing an opinion about whether the sleeps should be terminated prematurely during shutdown. But I am expressing a strong opinion about whether sleepers should do a reality check before proceeding. John -- John Polstra jdp@polstra.com John D. Polstra & Co., Inc. Seattle, Washington USA "Disappointment is a good sign of basic intelligence." -- Chögyam Trungpa To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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