RCU, IBM, Sequent, and Paul McKenney
Posted Jun 13, 2003 17:18 UTC (Fri) by ncm
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
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
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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