Commit 872aa4de authored by K Prateek Nayak's avatar K Prateek Nayak Committed by Peter Zijlstra
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sched/fair: Use READ_ONCE() to read sg->asym_prefer_cpu 



Subsequent commits add the support to dynamically update the sched_group
struct's "asym_prefer_cpu" member from a remote CPU. Use READ_ONCE()
when reading the "sg->asym_prefer_cpu" to ensure load balancer always
reads the latest value.

Signed-off-by: default avatarK Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250409053446.23367-2-kprateek.nayak@amd.com
parent 6432e163

kernel/sched/fair.c

+3 −2
Original line number Diff line number Diff line
@@ -10251,7 +10251,7 @@ sched_group_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group 
	    (sgs->group_weight - sgs->idle_cpus != 1))

		return false;



	return sched_asym(env->sd, env->dst_cpu, group->asym_prefer_cpu);

	return sched_asym(env->sd, env->dst_cpu, READ_ONCE(group->asym_prefer_cpu));

}



/* One group has more than one SMT CPU while the other group does not */
@@ -10488,7 +10488,8 @@ static bool update_sd_pick_busiest(struct lb_env *env, 


	case group_asym_packing:

		/* Prefer to move from lowest priority CPU's work */

		return sched_asym_prefer(sds->busiest->asym_prefer_cpu, sg->asym_prefer_cpu);

		return sched_asym_prefer(READ_ONCE(sds->busiest->asym_prefer_cpu),

					 READ_ONCE(sg->asym_prefer_cpu));



	case group_misfit_task:

		/*