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

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

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.
Paolo

> 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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