Miscellaneous scheduler fixes:

- Fix a timestamping bug in pick_task_fair() and
    yield_task_fair() (Zhan Xusheng)
 
  - Skip migrate-disabled tasks when picking a push
    candidate in the RT and DL schedulers (Seiji Nishikawa)
 
  - Skip rq->avg_idle update without a valid idle_stamp
    (Shubhang Kaushik)
 
  - Fix throttling bug in throttle_cfs_rq(), caused
    by the recent single-runqueue conversion (Wanwu Li)
 
  - Fix bandwidth calculation bug in distribute_cfs_runtime(),
    caused by the single-runqueue conversion (Wanwu Li)
 
  - Don't make x86 ITMT enablement depend on debugfs (Mario Limonciello)
 
  - Avoid creating misfits during cache-aware load-balancing
    on hybrid systems (Tim Chen)
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-urgent-2026-09-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Ingo Molnar:

 - Fix a timestamping bug in pick_task_fair() and yield_task_fair()
   (Zhan Xusheng)

 - Skip migrate-disabled tasks when picking a push candidate in the
   RT and DL schedulers (Seiji Nishikawa)

 - Skip rq->avg_idle update without a valid idle_stamp (Shubhang
   Kaushik)

 - Fix throttling bug in throttle_cfs_rq(), caused by the recent
   single-runqueue conversion (Wanwu Li)

 - Fix bandwidth calculation bug in distribute_cfs_runtime(),
   caused by the single-runqueue conversion (Wanwu Li)

 - Don't make x86 ITMT enablement depend on debugfs (Mario Limonciello)

 - Avoid creating misfits during cache-aware load-balancing on hybrid
   systems (Tim Chen)

* tag 'sched-urgent-2026-09-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Avoid creating misfits during cache-aware balancing
  x86/itmt: Don't make ITMT enablement depend on debugfs
  sched/fair: Use cfs_rq->h_curr in distribute_cfs_runtime()
  sched/fair: Use cfs_rq->h_curr in throttle_cfs_rq()
  sched/core: Skip rq->avg_idle update without a valid idle_stamp
  sched/rt,dl: Skip migrate-disabled tasks when picking a push candidate
  sched/fair: Use update_curr_eevdf() for the remaining root cfs_rq callers

arch/x86/kernel/itmt.c

@@ -110,18 +110,14 @@ int sched_set_itmt_support(void)
 						    arch_debugfs_dir,
 						    &sysctl_sched_itmt_enabled,
 						    &dfs_sched_itmt_fops);
-	if (IS_ERR_OR_NULL(dfs_sched_itmt)) {
+	if (IS_ERR(dfs_sched_itmt))
 		dfs_sched_itmt = NULL;
-		return -ENOMEM;
-	}
 
 	dfs_sched_core_prio = debugfs_create_file("sched_core_priority", 0644,
 						  arch_debugfs_dir, NULL,
 						  &sched_core_priority_fops);
-	if (IS_ERR_OR_NULL(dfs_sched_core_prio)) {
+	if (IS_ERR(dfs_sched_core_prio))
 		dfs_sched_core_prio = NULL;
-		return -ENOMEM;
-	}
 
 	sched_itmt_capable = true;
 

kernel/sched/core.c

@@ -3742,11 +3742,17 @@ static inline void ttwu_do_wakeup(struct task_struct *p)
 
 void update_rq_avg_idle(struct rq *rq)
 {
-	u64 delta = rq_clock(rq) - rq->idle_stamp;
-	u64 max = 2*rq->max_idle_balance_cost;
+	u64 idle_stamp = rq->idle_stamp;
+	u64 delta, max;
+
+	if (!idle_stamp)
+		return;
+
+	delta = rq_clock(rq) - idle_stamp;
 
 	update_avg(&rq->avg_idle, delta);
 
+	max = 2 * rq->max_idle_balance_cost;
 	if (rq->avg_idle > max)
 		rq->avg_idle = max;
 	rq->idle_stamp = 0;

kernel/sched/deadline.c

@@ -3028,8 +3028,8 @@ static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
 	next_node = rb_first_cached(&rq->dl.pushable_dl_tasks_root);
 	while (next_node) {
 		i = __node_2_pdl(next_node);
-		/* make sure task isn't on_cpu (possible with proxy-exec) */
-		if (!task_on_cpu(rq, i)) {
+		/* skip tasks that cannot be migrated */
+		if (!task_on_cpu(rq, i) && !is_migration_disabled(i)) {
 			p = i;
 			break;
 		}

kernel/sched/fair.c

@@ -6978,14 +6978,14 @@ static int tg_throttle_down(struct task_group *tg, void *data)
 static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
 {
 	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
-	struct sched_entity *curr = cfs_rq->curr;
+	struct sched_entity *curr = cfs_rq->h_curr;
 	struct rq *rq = rq_of(cfs_rq);
 
 	scoped_guard(raw_spinlock, &cfs_b->lock) {
 		u64 target_runtime = 1;
 
 		/*
-		 * If cfs_rq->curr is still runnable, we are here from an
+		 * If cfs_rq->h_curr is still runnable, we are here from an
 		 * update_curr(). Request sysctl_sched_cfs_bandwidth_slice
 		 * worth of bandwidth to continue running.
 		 *
@@ -7192,7 +7192,7 @@ static bool distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
 		if (!list_empty(&cfs_rq->throttled_csd_list))
 			continue;
 
-		if (cfs_rq->curr) {
+		if (cfs_rq->h_curr) {
 			update_rq_clock(rq);
 			update_curr(cfs_rq);
 		}
@@ -10057,7 +10057,7 @@ struct task_struct *pick_task_fair(struct rq *rq, struct rq_flags *rf)
 
 	/* Might not have done put_prev_entity() */
 	if (cfs_rq->curr && cfs_rq->curr->on_rq)
-		update_curr(cfs_rq);
+		update_curr_eevdf(cfs_rq);
 
 	se = pick_next_entity(rq, true);
 	if (!se)
@@ -10160,7 +10160,7 @@ static void yield_task_fair(struct rq *rq)
 	/*
 	 * Update run-time statistics of the 'current'.
 	 */
-	update_curr(cfs_rq);
+	update_curr_eevdf(cfs_rq);
 	/*
 	 * Tell update_rq_clock() that we've just updated,
 	 * so we don't do microscopic update in schedule()
@@ -10691,17 +10691,40 @@ static enum llc_mig can_migrate_llc(int src_cpu, int dst_cpu,
 	return mig_llc;
 }
 
+static inline bool task_misfits_asym_cpu(struct lb_env *env, struct task_struct *p)
+{
+	/*
+	 * On asymmetric CPU capacity domains, do not let cache-aware
+	 * balancing pull the task onto a destination CPU that cannot
+	 * accommodate it. Doing so would turn the task into a misfit on
+	 * the destination, trading a cache-locality gain for a capacity
+	 * loss. If the task already does not fit its source CPU, the move
+	 * cannot make things worse, so let the LLC preference decide.
+	 */
+	if ((env->sd->flags & SD_ASYM_CPUCAPACITY) && p &&
+	    !task_fits_cpu(p, env->dst_cpu) &&
+	    task_fits_cpu(p, env->src_cpu))
+		return true;
+
+	return false;
+}
+
 /*
  * Check if task p can migrate from source LLC to
  * destination LLC in terms of cache aware load balance.
  */
-static enum llc_mig can_migrate_llc_task(int src_cpu, int dst_cpu,
+static enum llc_mig can_migrate_llc_task(struct lb_env *env,
 					 struct task_struct *p)
 {
 	struct mm_struct *mm;
 	bool to_pref;
-	int cpu;
+	int cpu, src_cpu, dst_cpu;
 
+	if (task_misfits_asym_cpu(env, p))
+		return mig_forbid;
+
+	src_cpu = env->src_cpu;
+	dst_cpu = env->dst_cpu;
 	mm = p->mm;
 	if (!mm)
 		return mig_unrestricted;
@@ -10758,6 +10781,14 @@ alb_break_llc(struct lb_env *env)
 		unsigned long util = 0;
 		struct task_struct *cur;
 
+		/*
+		 * Migrating misfit tasks from current CPU
+		 * to CPU with a better fit.
+		 * Prioritize that over LLC preference.
+		 */
+		if (env->migration_type == migrate_misfit)
+			return false;
+
 		if (env->src_rq->nr_running <= 1)
 			return true;
 
@@ -10765,7 +10796,8 @@ alb_break_llc(struct lb_env *env)
 		if (cur && cur->sched_class == &fair_sched_class)
 			util = task_util(cur);
 
-		if (can_migrate_llc(env->src_cpu, env->dst_cpu,
+		if (task_misfits_asym_cpu(env, cur) ||
+		    can_migrate_llc(env->src_cpu, env->dst_cpu,
 				    util, false) == mig_forbid)
 			return true;
 	}
@@ -10805,8 +10837,7 @@ static bool migrate_degrades_llc(struct task_struct *p, struct lb_env *env)
 	    READ_ONCE(p->preferred_llc) != llc_id(env->dst_cpu))
 		return true;
 
-	if (can_migrate_llc_task(env->src_cpu,
-				 env->dst_cpu, p) != mig_forbid)
+	if (can_migrate_llc_task(env, p) != mig_forbid)
 		return false;
 
 	return true;
@@ -11869,6 +11900,15 @@ static inline bool llc_balance(struct lb_env *env, struct sg_lb_stats *sgs,
 	if (env->sd->flags & SD_SHARE_LLC)
 		return false;
 
+	/*
+	 * On asymmetric domains, group_misfit_task_load
+	 * should be prioritized to move tasks to CPU that fit them
+	 * over aggregating tasks to their preferred LLC.
+	 */
+	if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
+	    sgs->group_misfit_task_load)
+		return false;
+
 	/*
 	 * Skip cache aware tagging if nr_balanced_failed is sufficiently high.
 	 * Threshold of cache_nice_tries is set to 1 higher than nr_balance_failed

kernel/sched/rt.c

@@ -1872,8 +1872,8 @@ static struct task_struct *pick_next_pushable_task(struct rq *rq)
 		return NULL;
 
 	plist_for_each_entry(i, head, pushable_tasks) {
-		/* make sure task isn't on_cpu (possible with proxy-exec) */
-		if (!task_on_cpu(rq, i)) {
+		/* skip tasks that cannot be migrated */
+		if (!task_on_cpu(rq, i) && !is_migration_disabled(i)) {
 			p = i;
 			break;
 		}