Re: [PATCH RFC 4/5] sched/topology: Annonate RCU pointers properly

[Peter Zijlstra]

On Thu, Feb 21, 2019 at 12:49:41AM -0500, Joel Fernandes (Google) wrote:

> Also replace rcu_assign_pointer call on rq->sd with WRITE_ONCE. This
> should be sufficient for the rq->sd initialization.

> @@ -668,7 +668,7 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
>  
>  	rq_attach_root(rq, rd);
>  	tmp = rq->sd;
> -	rcu_assign_pointer(rq->sd, sd);
> +	WRITE_ONCE(rq->sd, sd);
>  	dirty_sched_domain_sysctl(cpu);
>  	destroy_sched_domains(tmp);

Where did the RELEASE barrier go?

That was a publish operation, now it is not.