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Re: [Xen-devel] [PATCH 06/11] qspinlock: Optimize pending bit

Il 15/06/2014 14:47, Peter Zijlstra ha scritto:
XXX: merge into the pending bit patch..

Agree, or if not move it right after the pending bit patch, before the NR_CPUS optimization.


It is possible so observe the pending bit without the locked bit when
the last owner has just released but the pending owner has not yet
taken ownership.

In this case we would normally queue -- because the pending bit is
already taken. However, in this case the pending bit is guaranteed to
be released 'soon', therefore wait for it and avoid queueing.

Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

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