Re: [RFC PATCH 0/7] priority-boost urcu
From: Paolo Bonzini
Date: Mon Aug 22 2011 - 05:11:17 EST
On 08/18/2011 03:30 PM, Steven Rostedt wrote:
In QEMU I added the manual-reset event and use it in the
implementation of RCU.
That was me. :)
Be careful with this. You better make sure that Microsoft does not hold
any patents to this method, otherwise all your work will be in vain.
I found the synchronization primitive mentioned in a patent filed 1994,
so I would be surprised if the primitive itself is younger than 20 years
(or even younger than 30 years in fact).
The only possibly novel thing is the userspace-only path when there is
no contention. Windows events always do a system call, so there is some
hope it isn't patented.
But if Microsoft did have a patent and it applied, both the
userspace-RCU and QEMU code would have a problem. The technique is the
same independent of whether you call futex primitives directly, or you
wrap them in an API.
Paolo
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