Re: [PATCH v2 2/4] sched/fair: add util_est on top of PELT

[Peter Zijlstra]

On Tue, Dec 05, 2017 at 05:10:16PM +0000, Patrick Bellasi wrote:
> +	if (cfs_rq->nr_running > 0) {
> +		util_est  = cfs_rq->util_est_runnable;
> +		util_est -= task_util_est(p);
> +		if (util_est < 0)
> +			util_est = 0;
> +		cfs_rq->util_est_runnable = util_est;
> +	} else {

I'm thinking that's an explicit load-store to avoid intermediate values
landing in cfs_rq->util_esp_runnable, right?

That would need READ_ONCE() / WRITE_ONCE() I think, without that the
compiler is free to munge the lot together.