Date: Mon, 18 Dec 2000 13:14:50 -0700 From: Chuck Paterson <cp@bsdi.com> To: Julian Elischer <julian@elischer.org> Cc: smp@FreeBSD.ORG Subject: Re: Netgraph locking primatives. take 1. Message-ID: <200012182014.eBIKEoP22868@berserker.bsdi.com> In-Reply-To: Your message of "Mon, 18 Dec 2000 05:59:44 PST." <3A3E1850.671A4AE2@elischer.org>
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Julian, I read your mail and looked at your example and still am not sure if there is a problem. In the last email I used the word process several times when it really isn't the right notion with respect to messages. It should really be processes and/or message. The thread of control in this case is a message, not a process. It may not be a process that hangs, but rather a pair of messages that can never make progress. You said that if you are running in node X then you hold a reader lock on node X. This means that code running in node X can never get a writer lock, if it is to avoid deadlock. I think what needs to happen is that if you are running in node X you must hold a reader or writer lock. Both the decision of which type of lock is needed and the acquistion of the lock must be made before entering the node. As I said I looked through your mail and the example and could not tell for sure where you were at. Sorry if I am just saying the samething you were talking about. Chuck To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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