Date: Thu, 05 Dec 1996 11:04:17 -0700 From: Steve Passe <smp@csn.net> To: vanmaren@fast.cs.utah.edu (Kevin Van Maren) Cc: ccsanady@friley216.res.iastate.edu, peter@spinner.dialix.com, smp@freebsd.org Subject: Re: make locking more generic? Message-ID: <199612051804.LAA13790@clem.systemsix.com> In-Reply-To: Your message of "Thu, 05 Dec 1996 10:59:01 MST." <199612051759.KAA19283@fast.cs.utah.edu>
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Hi, > If you have a driver that is used for two devices, and you > allow both to generate interrupts and have the driver executing > on two processors simultaneously, the shared data structures > are not going to be protected. So the simple fix would be to > put a lock around each driver. But you will still have > problems with other shared data structures; the same problem > with allowing multiple processes to make kernel calls. one thing to know about is that the APIC has a notion of 'focus processor'. this means that if a CPU is currently servicing a specific IRQ, if that IRQ is generated again the request is sent to that CPU, reguardless of TPR and/or PPR > This is all part of the enormous problem of adding fine-grained > locking to an existing single-threaded kernel. yes, it will be a HUGE task to get it right! -- Steve Passe | powered by smp@csn.net | FreeBSD -----BEGIN PGP PUBLIC KEY BLOCK----- Version: 2.6.2 mQCNAzHe7tEAAAEEAM274wAEEdP+grIrV6UtBt54FB5ufifFRA5ujzflrvlF8aoE 04it5BsUPFi3jJLfvOQeydbegexspPXL6kUejYt2OeptHuroIVW5+y2M2naTwqtX WVGeBP6s2q/fPPAS+g+sNZCpVBTbuinKa/C4Q6HJ++M9AyzIq5EuvO0a8Rr9AAUR tBlTdGV2ZSBQYXNzZSA8c21wQGNzbi5uZXQ+ =ds99 -----END PGP PUBLIC KEY BLOCK-----
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