Messages in this thread | | | From | Nikita Danilov <> | Date | Sat, 24 Mar 2007 18:55:04 +0300 | Subject | Re: [rfc][patch] queued spinlocks (i386) |
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Nick Piggin writes: > On Fri, Mar 23, 2007 at 11:04:18AM +0100, Ingo Molnar wrote: > > > > * Nick Piggin <npiggin@suse.de> wrote: > > > > > Implement queued spinlocks for i386. [...] > > > > isnt this patented by MS? (which might not worry you SuSE/Novell guys, > > but it might be a worry for the rest of the world ;-) > > Hmm, it looks like they have implemented a system where the spinning > cpu sleeps on a per-CPU variable rather than the lock itself, and > the releasing cpu writes to that variable to wake it. They do this > so that spinners don't continually perform exclusive->shared > transitions on the lock cacheline. They call these things queued > spinlocks. They don't seem to be very patent worthy either, but
Indeed, this technique is very well known. E.g., http://citeseer.ist.psu.edu/anderson01sharedmemory.html has a whole section (3. Local-spin Algorithms) on them, citing papers from the 1990 onward.
Nikita.
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