1 files changed, 18 insertions, 13 deletions

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index ab7f371a3a17..f53f89df837d 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -615,13 +615,13 @@ static void destroy_sched_domains(struct sched_domain *sd)
  * the cpumask of the domain), this allows us to quickly tell if
  * two CPUs are in the same cache domain, see cpus_share_cache().
  */
-DEFINE_PER_CPU(struct sched_domain *, sd_llc);
+DEFINE_PER_CPU(struct sched_domain __rcu *, sd_llc);
 DEFINE_PER_CPU(int, sd_llc_size);
 DEFINE_PER_CPU(int, sd_llc_id);
-DEFINE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);
-DEFINE_PER_CPU(struct sched_domain *, sd_numa);
-DEFINE_PER_CPU(struct sched_domain *, sd_asym_packing);
-DEFINE_PER_CPU(struct sched_domain *, sd_asym_cpucapacity);
+DEFINE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared);
+DEFINE_PER_CPU(struct sched_domain __rcu *, sd_numa);
+DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
+DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
 DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity);
 
 static void update_top_cache_domain(int cpu)
@@ -1059,6 +1059,7 @@ static struct sched_group *get_group(int cpu, struct sd_data *sdd)
         struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
         struct sched_domain *child = sd->child;
         struct sched_group *sg;
+        bool already_visited;
 
         if (child)
                 cpu = cpumask_first(sched_domain_span(child));
@@ -1066,9 +1067,14 @@ static struct sched_group *get_group(int cpu, struct sd_data *sdd)
         sg = *per_cpu_ptr(sdd->sg, cpu);
         sg->sgc = *per_cpu_ptr(sdd->sgc, cpu);
 
-        /* For claim_allocations: */
-        atomic_inc(&sg->ref);
-        atomic_inc(&sg->sgc->ref);
+        /* Increase refcounts for claim_allocations: */
+        already_visited = atomic_inc_return(&sg->ref) > 1;
+        /* sgc visits should follow a similar trend as sg */
+        WARN_ON(already_visited != (atomic_inc_return(&sg->sgc->ref) > 1));
+
+        /* If we have already visited that group, it's already initialized. */
+        if (already_visited)
+                return sg;
 
         if (child) {
                 cpumask_copy(sched_group_span(sg), sched_domain_span(child));
@@ -1087,8 +1093,8 @@ static struct sched_group *get_group(int cpu, struct sd_data *sdd)
 
 /*
  * build_sched_groups will build a circular linked list of the groups
- * covered by the given span, and will set each group's ->cpumask correctly,
- * and ->cpu_capacity to 0.
+ * covered by the given span, will set each group's ->cpumask correctly,
+ * and will initialize their ->sgc.
  *
  * Assumes the sched_domain tree is fully constructed
  */
@@ -2075,9 +2081,8 @@ void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
 }
 
 /*
- * Set up scheduler domains and groups. Callers must hold the hotplug lock.
- * For now this just excludes isolated CPUs, but could be used to
- * exclude other special cases in the future.
+ * Set up scheduler domains and groups.  For now this just excludes isolated
+ * CPUs, but could be used to exclude other special cases in the future.
  */
 int sched_init_domains(const struct cpumask *cpu_map)
 {