Merge tag 'sched-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Fix inconsistency in misfit task load-balancing

 - Fix CPU isolation bugs in the task-wakeup logic

 - Rework and unify the sched_use_asym_prio() and sched_asym_prefer()
   logic

 - Clean up and simplify ->avg_* accesses

 - Misc cleanups and fixes

* tag 'sched-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/topology: Rename SD_SHARE_PKG_RESOURCES to SD_SHARE_LLC
  sched/fair: Check the SD_ASYM_PACKING flag in sched_use_asym_prio()
  sched/fair: Rework sched_use_asym_prio() and sched_asym_prefer()
  sched/fair: Remove unused parameter from sched_asym()
  sched/topology: Remove duplicate descriptions from TOPOLOGY_SD_FLAGS
  sched/fair: Simplify the update_sd_pick_busiest() logic
  sched/fair: Do strict inequality check for busiest misfit task group
  sched/fair: Remove unnecessary goto in update_sd_lb_stats()
  sched/fair: Take the scheduling domain into account in select_idle_core()
  sched/fair: Take the scheduling domain into account in select_idle_smt()
  sched/fair: Add READ_ONCE() and use existing helper function to access ->avg_irq
  sched/fair: Use existing helper functions to access ->avg_rt and ->avg_dl
  sched/core: Simplify code by removing duplicate #ifdefs

arch/powerpc/kernel/smp.c

@@ -984,7 +984,7 @@ static bool shared_caches __ro_after_init;
 /* cpumask of CPUs with asymmetric SMT dependency */
 static int powerpc_smt_flags(void)
 {
-	int flags = SD_SHARE_CPUCAPACITY | SD_SHARE_PKG_RESOURCES;
+	int flags = SD_SHARE_CPUCAPACITY | SD_SHARE_LLC;
 
 	if (cpu_has_feature(CPU_FTR_ASYM_SMT)) {
 		printk_once(KERN_INFO "Enabling Asymmetric SMT scheduling\n");
@@ -1010,9 +1010,9 @@ static __ro_after_init DEFINE_STATIC_KEY_FALSE(splpar_asym_pack);
 static int powerpc_shared_cache_flags(void)
 {
 	if (static_branch_unlikely(&splpar_asym_pack))
-		return SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING;
+		return SD_SHARE_LLC | SD_ASYM_PACKING;
 
-	return SD_SHARE_PKG_RESOURCES;
+	return SD_SHARE_LLC;
 }
 
 static int powerpc_shared_proc_flags(void)

include/linux/sched/sd_flags.h

@@ -117,13 +117,13 @@ SD_FLAG(SD_SHARE_CPUCAPACITY, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
 SD_FLAG(SD_CLUSTER, SDF_NEEDS_GROUPS)
 
 /*
- * Domain members share CPU package resources (i.e. caches)
+ * Domain members share CPU Last Level Caches
  *
  * SHARED_CHILD: Set from the base domain up until spanned CPUs no longer share
  *               the same cache(s).
  * NEEDS_GROUPS: Caches are shared between groups.
  */
-SD_FLAG(SD_SHARE_PKG_RESOURCES, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
+SD_FLAG(SD_SHARE_LLC, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
 
 /*
  * Only a single load balancing instance

include/linux/sched/topology.h

@@ -38,21 +38,21 @@ extern const struct sd_flag_debug sd_flag_debug[];
 #ifdef CONFIG_SCHED_SMT
 static inline int cpu_smt_flags(void)
 {
-	return SD_SHARE_CPUCAPACITY | SD_SHARE_PKG_RESOURCES;
+	return SD_SHARE_CPUCAPACITY | SD_SHARE_LLC;
 }
 #endif
 
 #ifdef CONFIG_SCHED_CLUSTER
 static inline int cpu_cluster_flags(void)
 {
-	return SD_CLUSTER | SD_SHARE_PKG_RESOURCES;
+	return SD_CLUSTER | SD_SHARE_LLC;
 }
 #endif
 
 #ifdef CONFIG_SCHED_MC
 static inline int cpu_core_flags(void)
 {
-	return SD_SHARE_PKG_RESOURCES;
+	return SD_SHARE_LLC;
 }
 #endif
 

kernel/sched/core.c

@@ -1792,7 +1792,6 @@ static void cpu_util_update_eff(struct cgroup_subsys_state *css);
 #endif
 
 #ifdef CONFIG_SYSCTL
-#ifdef CONFIG_UCLAMP_TASK
 #ifdef CONFIG_UCLAMP_TASK_GROUP
 static void uclamp_update_root_tg(void)
 {
@@ -1898,7 +1897,6 @@ static int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
 	return result;
 }
 #endif
-#endif
 
 static int uclamp_validate(struct task_struct *p,
 			   const struct sched_attr *attr)
@@ -2065,7 +2063,7 @@ static void __init init_uclamp(void)
 	}
 }
 
-#else /* CONFIG_UCLAMP_TASK */
+#else /* !CONFIG_UCLAMP_TASK */
 static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { }
 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
 static inline int uclamp_validate(struct task_struct *p,

kernel/sched/fair.c

@@ -7289,7 +7289,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
 		if (!available_idle_cpu(cpu)) {
 			idle = false;
 			if (*idle_cpu == -1) {
-				if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
+				if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, cpus)) {
 					*idle_cpu = cpu;
 					break;
 				}
@@ -7297,7 +7297,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
 			}
 			break;
 		}
-		if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
+		if (*idle_cpu == -1 && cpumask_test_cpu(cpu, cpus))
 			*idle_cpu = cpu;
 	}
 
@@ -7311,13 +7311,19 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
 /*
  * Scan the local SMT mask for idle CPUs.
  */
-static int select_idle_smt(struct task_struct *p, int target)
+static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
 	int cpu;
 
 	for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
 		if (cpu == target)
 			continue;
+		/*
+		 * Check if the CPU is in the LLC scheduling domain of @target.
+		 * Due to isolcpus, there is no guarantee that all the siblings are in the domain.
+		 */
+		if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
+			continue;
 		if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
 			return cpu;
 	}
@@ -7341,7 +7347,7 @@ static inline int select_idle_core(struct task_struct *p, int core, struct cpuma
 	return __select_idle_cpu(core, p);
 }
 
-static inline int select_idle_smt(struct task_struct *p, int target)
+static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
 	return -1;
 }
@@ -7591,7 +7597,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 		has_idle_core = test_idle_cores(target);
 
 		if (!has_idle_core && cpus_share_cache(prev, target)) {
-			i = select_idle_smt(p, prev);
+			i = select_idle_smt(p, sd, prev);
 			if ((unsigned int)i < nr_cpumask_bits)
 				return i;
 		}
@@ -9237,19 +9243,17 @@ static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
 
 static inline bool others_have_blocked(struct rq *rq)
 {
-	if (READ_ONCE(rq->avg_rt.util_avg))
+	if (cpu_util_rt(rq))
 		return true;
 
-	if (READ_ONCE(rq->avg_dl.util_avg))
+	if (cpu_util_dl(rq))
 		return true;
 
 	if (thermal_load_avg(rq))
 		return true;
 
-#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
-	if (READ_ONCE(rq->avg_irq.util_avg))
+	if (cpu_util_irq(rq))
 		return true;
-#endif
 
 	return false;
 }
@@ -9506,8 +9510,8 @@ static unsigned long scale_rt_capacity(int cpu)
 	 * avg_thermal.load_avg tracks thermal pressure and the weighted
 	 * average uses the actual delta max capacity(load).
 	 */
-	used = READ_ONCE(rq->avg_rt.util_avg);
-	used += READ_ONCE(rq->avg_dl.util_avg);
+	used = cpu_util_rt(rq);
+	used += cpu_util_dl(rq);
 	used += thermal_load_avg(rq);
 
 	if (unlikely(used >= max))
@@ -9740,51 +9744,49 @@ group_type group_classify(unsigned int imbalance_pct,
  */
 static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
 {
+	if (!(sd->flags & SD_ASYM_PACKING))
+		return false;
+
 	if (!sched_smt_active())
 		return true;
 
 	return sd->flags & SD_SHARE_CPUCAPACITY || is_core_idle(cpu);
 }
 
+static inline bool sched_asym(struct sched_domain *sd, int dst_cpu, int src_cpu)
+{
+	/*
+	 * First check if @dst_cpu can do asym_packing load balance. Only do it
+	 * if it has higher priority than @src_cpu.
+	 */
+	return sched_use_asym_prio(sd, dst_cpu) &&
+		sched_asym_prefer(dst_cpu, src_cpu);
+}
+
 /**
- * sched_asym - Check if the destination CPU can do asym_packing load balance
+ * sched_group_asym - Check if the destination CPU can do asym_packing balance
  * @env:	The load balancing environment
- * @sds:	Load-balancing data with statistics of the local group
  * @sgs:	Load-balancing statistics of the candidate busiest group
  * @group:	The candidate busiest group
  *
  * @env::dst_cpu can do asym_packing if it has higher priority than the
  * preferred CPU of @group.
  *
- * SMT is a special case. If we are balancing load between cores, @env::dst_cpu
- * can do asym_packing balance only if all its SMT siblings are idle. Also, it
- * can only do it if @group is an SMT group and has exactly on busy CPU. Larger
- * imbalances in the number of CPUS are dealt with in find_busiest_group().
- *
- * If we are balancing load within an SMT core, or at PKG domain level, always
- * proceed.
- *
  * Return: true if @env::dst_cpu can do with asym_packing load balance. False
  * otherwise.
  */
 static inline bool
-sched_asym(struct lb_env *env, struct sd_lb_stats *sds,  struct sg_lb_stats *sgs,
-	   struct sched_group *group)
+sched_group_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group)
 {
-	/* Ensure that the whole local core is idle, if applicable. */
-	if (!sched_use_asym_prio(env->sd, env->dst_cpu))
-		return false;
-
 	/*
-	 * CPU priorities does not make sense for SMT cores with more than one
+	 * CPU priorities do not make sense for SMT cores with more than one
 	 * busy sibling.
 	 */
-	if (group->flags & SD_SHARE_CPUCAPACITY) {
-		if (sgs->group_weight - sgs->idle_cpus != 1)
-			return false;
-	}
+	if ((group->flags & SD_SHARE_CPUCAPACITY) &&
+	    (sgs->group_weight - sgs->idle_cpus != 1))
+		return false;
 
-	return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu);
+	return sched_asym(env->sd, env->dst_cpu, group->asym_prefer_cpu);
 }
 
 /* One group has more than one SMT CPU while the other group does not */
@@ -9938,11 +9940,9 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 	sgs->group_weight = group->group_weight;
 
 	/* Check if dst CPU is idle and preferred to this group */
-	if (!local_group && env->sd->flags & SD_ASYM_PACKING &&
-	    env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
-	    sched_asym(env, sds, sgs, group)) {
+	if (!local_group && env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
+	    sched_group_asym(env, sgs, group))
 		sgs->group_asym_packing = 1;
-	}
 
 	/* Check for loaded SMT group to be balanced to dst CPU */
 	if (!local_group && smt_balance(env, sgs, group))
@@ -10006,9 +10006,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
 	switch (sgs->group_type) {
 	case group_overloaded:
 		/* Select the overloaded group with highest avg_load. */
-		if (sgs->avg_load <= busiest->avg_load)
-			return false;
-		break;
+		return sgs->avg_load > busiest->avg_load;
 
 	case group_imbalanced:
 		/*
@@ -10019,18 +10017,14 @@ static bool update_sd_pick_busiest(struct lb_env *env,
 
 	case group_asym_packing:
 		/* Prefer to move from lowest priority CPU's work */
-		if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu))
-			return false;
-		break;
+		return sched_asym_prefer(sds->busiest->asym_prefer_cpu, sg->asym_prefer_cpu);
 
 	case group_misfit_task:
 		/*
 		 * If we have more than one misfit sg go with the biggest
 		 * misfit.
 		 */
-		if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
-			return false;
-		break;
+		return sgs->group_misfit_task_load > busiest->group_misfit_task_load;
 
 	case group_smt_balance:
 		/*
@@ -10182,10 +10176,8 @@ static int idle_cpu_without(int cpu, struct task_struct *p)
 	 * be computed and tested before calling idle_cpu_without().
 	 */
 
-#ifdef CONFIG_SMP
 	if (rq->ttwu_pending)
 		return 0;
-#endif
 
 	return 1;
 }
@@ -10578,16 +10570,11 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
 
 		update_sg_lb_stats(env, sds, sg, sgs, &sg_status);
 
-		if (local_group)
-			goto next_group;
-
-
-		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
+		if (!local_group && update_sd_pick_busiest(env, sds, sg, sgs)) {
 			sds->busiest = sg;
 			sds->busiest_stat = *sgs;
 		}
 
-next_group:
 		/* Now, start updating sd_lb_stats */
 		sds->total_load += sgs->group_load;
 		sds->total_capacity += sgs->group_capacity;
@@ -10691,7 +10678,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 	 */
 	if (local->group_type == group_has_spare) {
 		if ((busiest->group_type > group_fully_busy) &&
-		    !(env->sd->flags & SD_SHARE_PKG_RESOURCES)) {
+		    !(env->sd->flags & SD_SHARE_LLC)) {
 			/*
 			 * If busiest is overloaded, try to fill spare
 			 * capacity. This might end up creating spare capacity
@@ -11038,10 +11025,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 		 * If balancing between cores, let lower priority CPUs help
 		 * SMT cores with more than one busy sibling.
 		 */
-		if ((env->sd->flags & SD_ASYM_PACKING) &&
-		    sched_use_asym_prio(env->sd, i) &&
-		    sched_asym_prefer(i, env->dst_cpu) &&
-		    nr_running == 1)
+		if (sched_asym(env->sd, i, env->dst_cpu) && nr_running == 1)
 			continue;
 
 		switch (env->migration_type) {
@@ -11137,8 +11121,7 @@ asym_active_balance(struct lb_env *env)
 	 * the lower priority @env::dst_cpu help it. Do not follow
 	 * CPU priority.
 	 */
-	return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
-	       sched_use_asym_prio(env->sd, env->dst_cpu) &&
+	return env->idle != CPU_NOT_IDLE && sched_use_asym_prio(env->sd, env->dst_cpu) &&
 	       (sched_asym_prefer(env->dst_cpu, env->src_cpu) ||
 		!sched_use_asym_prio(env->sd, env->src_cpu));
 }
@@ -11910,8 +11893,7 @@ static void nohz_balancer_kick(struct rq *rq)
 		 * preferred CPU must be idle.
 		 */
 		for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
-			if (sched_use_asym_prio(sd, i) &&
-			    sched_asym_prefer(i, cpu)) {
+			if (sched_asym(sd, i, cpu)) {
 				flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
 				goto unlock;
 			}

kernel/sched/sched.h

@@ -3136,7 +3136,7 @@ static inline bool uclamp_rq_is_idle(struct rq *rq)
 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
 static inline unsigned long cpu_util_irq(struct rq *rq)
 {
-	return rq->avg_irq.util_avg;
+	return READ_ONCE(rq->avg_irq.util_avg);
 }
 
 static inline

kernel/sched/topology.c

@@ -657,13 +657,13 @@ static void destroy_sched_domains(struct sched_domain *sd)
 }
 
 /*
- * Keep a special pointer to the highest sched_domain that has
- * SD_SHARE_PKG_RESOURCE set (Last Level Cache Domain) for this
- * allows us to avoid some pointer chasing select_idle_sibling().
+ * Keep a special pointer to the highest sched_domain that has SD_SHARE_LLC set
+ * (Last Level Cache Domain) for this allows us to avoid some pointer chasing
+ * select_idle_sibling().
  *
- * Also keep a unique ID per domain (we use the first CPU number in
- * the cpumask of the domain), this allows us to quickly tell if
- * two CPUs are in the same cache domain, see cpus_share_cache().
+ * Also keep a unique ID per domain (we use the first CPU number in 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 __rcu *, sd_llc);
 DEFINE_PER_CPU(int, sd_llc_size);
@@ -684,7 +684,7 @@ static void update_top_cache_domain(int cpu)
 	int id = cpu;
 	int size = 1;
 
-	sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
+	sd = highest_flag_domain(cpu, SD_SHARE_LLC);
 	if (sd) {
 		id = cpumask_first(sched_domain_span(sd));
 		size = cpumask_weight(sched_domain_span(sd));
@@ -1551,11 +1551,12 @@ static struct cpumask		***sched_domains_numa_masks;
  *
  * These flags are purely descriptive of the topology and do not prescribe
  * behaviour. Behaviour is artificial and mapped in the below sd_init()
- * function:
+ * function. For details, see include/linux/sched/sd_flags.h.
  *
- *   SD_SHARE_CPUCAPACITY   - describes SMT topologies
- *   SD_SHARE_PKG_RESOURCES - describes shared caches
- *   SD_NUMA                - describes NUMA topologies
+ *   SD_SHARE_CPUCAPACITY
+ *   SD_SHARE_LLC
+ *   SD_CLUSTER
+ *   SD_NUMA
  *
  * Odd one out, which beside describing the topology has a quirk also
  * prescribes the desired behaviour that goes along with it:
@@ -1565,7 +1566,7 @@ static struct cpumask		***sched_domains_numa_masks;
 #define TOPOLOGY_SD_FLAGS		\
 	(SD_SHARE_CPUCAPACITY	|	\
 	 SD_CLUSTER		|	\
-	 SD_SHARE_PKG_RESOURCES |	\
+	 SD_SHARE_LLC		|	\
 	 SD_NUMA		|	\
 	 SD_ASYM_PACKING)
 
@@ -1608,7 +1609,7 @@ sd_init(struct sched_domain_topology_level *tl,
 					| 0*SD_BALANCE_WAKE
 					| 1*SD_WAKE_AFFINE
 					| 0*SD_SHARE_CPUCAPACITY
-					| 0*SD_SHARE_PKG_RESOURCES
+					| 0*SD_SHARE_LLC
 					| 0*SD_SERIALIZE
 					| 1*SD_PREFER_SIBLING
 					| 0*SD_NUMA
@@ -1645,7 +1646,7 @@ sd_init(struct sched_domain_topology_level *tl,
 	if (sd->flags & SD_SHARE_CPUCAPACITY) {
 		sd->imbalance_pct = 110;
 
-	} else if (sd->flags & SD_SHARE_PKG_RESOURCES) {
+	} else if (sd->flags & SD_SHARE_LLC) {
 		sd->imbalance_pct = 117;
 		sd->cache_nice_tries = 1;
 
@@ -1670,7 +1671,7 @@ sd_init(struct sched_domain_topology_level *tl,
 	 * For all levels sharing cache; connect a sched_domain_shared
 	 * instance.
 	 */
-	if (sd->flags & SD_SHARE_PKG_RESOURCES) {
+	if (sd->flags & SD_SHARE_LLC) {
 		sd->shared = *per_cpu_ptr(sdd->sds, sd_id);
 		atomic_inc(&sd->shared->ref);
 		atomic_set(&sd->shared->nr_busy_cpus, sd_weight);
@@ -2445,8 +2446,8 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
 		for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
 			struct sched_domain *child = sd->child;
 
-			if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child &&
-			    (child->flags & SD_SHARE_PKG_RESOURCES)) {
+			if (!(sd->flags & SD_SHARE_LLC) && child &&
+			    (child->flags & SD_SHARE_LLC)) {
 				struct sched_domain __rcu *top_p;
 				unsigned int nr_llcs;