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RCU, IBM, Sequent, and Paul McKenneyRCU, IBM, Sequent, and Paul McKenneyPosted Jun 13, 2003 17:18 UTC (Fri) by ncm (subscriber, #165)Parent article: Does SCO own read-copy-update? I went to school with Paul McKenney. He went off to work at Sequent a long time ago. While there, he and Slingwine invented RCU. (Somebody else at IBM invented it independently, later.) When IBM bought Sequent, they got Dynix, and Paul, and the patent. Paul started working on getting RCU usage incorporated into Linux a few years back. The mailing list archives reveal that for way too long, several of the kernel maintainers were unconscionably rude over what turned out to be differences of macro naming style. Now the RCU technique is used in a half dozen places in the kernel, and its use will probably continue to grow. It's a brilliant technique, and remarkably underreported. IBM has published a license allowing RCU to be used freely in GPLed code, but retains all other rights. The BSDs can't use it. One thing is certain, though: SCO doesn't own it. Interestingly, the patent implicitly forbids use of RCU in proprietary drivers. That is, the driver vendor would need a separate license from IBM. It's not clear whether proprietary drivers can even use the regular kernel header macros without a license. Incidentally, while at Sequent, Paul also did seminal work on SMP/NUMA memory allocators, and some of the principles he identified are about to be folded into GNU libstdc++ memory management. I think the kernel memory allocator has yet to be blessed with McKenney goodness.
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