[lttng-dev] [PATCH 5/8] urcu-mb/signal/membarrier: move quiescent threads to separate list

[Lai Jiangshan]

On 11/18/2012 12:16 AM, Mathieu Desnoyers wrote:
> Accelerate 2-phase grace period by not having to iterate twice on
> threads not nested within a RCU read-side lock.

You almost gain nothing.
The first wait_for_readers() waits none very likely.

> @@ -341,7 +361,12 @@ void synchronize_rcu(void)
>  	/*
>  	 * Wait for readers to observe new parity or be quiescent.
>  	 */
> -	wait_for_readers();
> +	wait_for_readers(&registry, NULL, &qsreaders);

wait_for_readers(&cur_snap_readers, NULL, &qsreaders);