On Mon, 2014-02-10 at 20:58 +0100, Peter Zijlstra wrote:
> +void osq_unlock(struct optimistic_spin_queue **lock)
> +{
> + struct optimistic_spin_queue *node = this_cpu_ptr(&osq_node);
> + struct optimistic_spin_queue *next;
> +
> + /*
> + * Fast path for the uncontended case.
> + */
> + if (likely(cmpxchg(lock, node, NULL) == node))
> + return;
Can we can also add the following code here as I'm noticing next != NULL
is the much more likely scenario on my box:
next = xchg(&node->next, NULL);
if (next) {
ACCESS_ONCE(next->locked) = 1;
return;
> + next = osq_wait_next(lock, node, NULL);
> + if (next)
> + ACCESS_ONCE(next->locked) = 1;
> +}
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