Merge tag 'sched-core-2025-12-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:
 "Scalability and load-balancing improvements:

   - Enable scheduler feature NEXT_BUDDY (Mel Gorman)

   - Reimplement NEXT_BUDDY to align with EEVDF goals (Mel Gorman)

   - Skip sched_balance_running cmpxchg when balance is not due (Tim
     Chen)

   - Implement generic code for architecture specific sched domain NUMA
     distances (Tim Chen)

   - Optimize the NUMA distances of the sched-domains builds of Intel
     Granite Rapids (GNR) and Clearwater Forest (CWF) platforms (Tim
     Chen)

   - Implement proportional newidle balance: a randomized algorithm that
     runs newidle balancing proportional to its success rate. (Peter
     Zijlstra)

  Scheduler infrastructure changes:

   - Implement the 'sched_change' scoped_guard() pattern for the entire
     scheduler (Peter Zijlstra)

   - More broadly utilize the sched_change guard (Peter Zijlstra)

   - Add support to pick functions to take runqueue-flags (Joel
     Fernandes)

   - Provide and use set_need_resched_current() (Peter Zijlstra)

  Fair scheduling enhancements:

   - Forfeit vruntime on yield (Fernand Sieber)

   - Only update stats for allowed CPUs when looking for dst group (Adam
     Li)

  CPU-core scheduling enhancements:

   - Optimize core cookie matching check (Fernand Sieber)

  Deadline scheduler fixes:

   - Only set free_cpus for online runqueues (Doug Berger)

   - Fix dl_server time accounting (Peter Zijlstra)

   - Fix dl_server stop condition (Peter Zijlstra)

  Proxy scheduling fixes:

   - Yield the donor task (Fernand Sieber)

  Fixes and cleanups:

   - Fix do_set_cpus_allowed() locking (Peter Zijlstra)

   - Fix migrate_disable_switch() locking (Peter Zijlstra)

   - Remove double update_rq_clock() in __set_cpus_allowed_ptr_locked()
     (Hao Jia)

   - Increase sched_tick_remote timeout (Phil Auld)

   - sched/deadline: Use cpumask_weight_and() in dl_bw_cpus() (Shrikanth
     Hegde)

   - sched/deadline: Clean up select_task_rq_dl() (Shrikanth Hegde)"

* tag 'sched-core-2025-12-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
  sched: Provide and use set_need_resched_current()
  sched/fair: Proportional newidle balance
  sched/fair: Small cleanup to update_newidle_cost()
  sched/fair: Small cleanup to sched_balance_newidle()
  sched/fair: Revert max_newidle_lb_cost bump
  sched/fair: Reimplement NEXT_BUDDY to align with EEVDF goals
  sched/fair: Enable scheduler feature NEXT_BUDDY
  sched: Increase sched_tick_remote timeout
  sched/fair: Have SD_SERIALIZE affect newidle balancing
  sched/fair: Skip sched_balance_running cmpxchg when balance is not due
  sched/deadline: Minor cleanup in select_task_rq_dl()
  sched/deadline: Use cpumask_weight_and() in dl_bw_cpus
  sched/deadline: Document dl_server
  sched/deadline: Fix dl_server stop condition
  sched/deadline: Fix dl_server time accounting
  sched/core: Remove double update_rq_clock() in __set_cpus_allowed_ptr_locked()
  sched/eevdf: Fix min_vruntime vs avg_vruntime
  sched/core: Add comment explaining force-idle vruntime snapshots
  sched/core: Optimize core cookie matching check
  sched/proxy: Yield the donor task
  ...

1 files changed, 28 insertions, 59 deletions

diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c
index 77ae87f36e84..807879131add 100644
--- a/kernel/sched/syscalls.c
+++ b/kernel/sched/syscalls.c
@@ -64,8 +64,6 @@ static int effective_prio(struct task_struct *p)
 
 void set_user_nice(struct task_struct *p, long nice)
 {
-	bool queued, running;
-	struct rq *rq;
 	int old_prio;
 
 	if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
@@ -74,10 +72,7 @@ void set_user_nice(struct task_struct *p, long nice)
 	 * We have to be careful, if called from sys_setpriority(),
 	 * the task might be in the middle of scheduling on another CPU.
 	 */
-	CLASS(task_rq_lock, rq_guard)(p);
-	rq = rq_guard.rq;
-
-	update_rq_clock(rq);
+	guard(task_rq_lock)(p);
 
 	/*
 	 * The RT priorities are set via sched_setscheduler(), but we still
@@ -90,28 +85,12 @@ void set_user_nice(struct task_struct *p, long nice)
 		return;
 	}
 
-	queued = task_on_rq_queued(p);
-	running = task_current_donor(rq, p);
-	if (queued)
-		dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
-	if (running)
-		put_prev_task(rq, p);
-
-	p->static_prio = NICE_TO_PRIO(nice);
-	set_load_weight(p, true);
-	old_prio = p->prio;
-	p->prio = effective_prio(p);
-
-	if (queued)
-		enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
-	if (running)
-		set_next_task(rq, p);
-
-	/*
-	 * If the task increased its priority or is running and
-	 * lowered its priority, then reschedule its CPU:
-	 */
-	p->sched_class->prio_changed(rq, p, old_prio);
+	scoped_guard (sched_change, p, DEQUEUE_SAVE) {
+		p->static_prio = NICE_TO_PRIO(nice);
+		set_load_weight(p, true);
+		old_prio = p->prio;
+		p->prio = effective_prio(p);
+	}
 }
 EXPORT_SYMBOL(set_user_nice);
 
@@ -515,7 +494,7 @@ int __sched_setscheduler(struct task_struct *p,
 			 bool user, bool pi)
 {
 	int oldpolicy = -1, policy = attr->sched_policy;
-	int retval, oldprio, newprio, queued, running;
+	int retval, oldprio, newprio;
 	const struct sched_class *prev_class, *next_class;
 	struct balance_callback *head;
 	struct rq_flags rf;
@@ -695,38 +674,27 @@ change:
 	prev_class = p->sched_class;
 	next_class = __setscheduler_class(policy, newprio);
 
-	if (prev_class != next_class && p->se.sched_delayed)
-		dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED | DEQUEUE_NOCLOCK);
-
-	queued = task_on_rq_queued(p);
-	running = task_current_donor(rq, p);
-	if (queued)
-		dequeue_task(rq, p, queue_flags);
-	if (running)
-		put_prev_task(rq, p);
+	if (prev_class != next_class)
+		queue_flags |= DEQUEUE_CLASS;
 
-	if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
-		__setscheduler_params(p, attr);
-		p->sched_class = next_class;
-		p->prio = newprio;
-	}
-	__setscheduler_uclamp(p, attr);
-	check_class_changing(rq, p, prev_class);
+	scoped_guard (sched_change, p, queue_flags) {
 
-	if (queued) {
-		/*
-		 * We enqueue to tail when the priority of a task is
-		 * increased (user space view).
-		 */
-		if (oldprio < p->prio)
-			queue_flags |= ENQUEUE_HEAD;
+		if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
+			__setscheduler_params(p, attr);
+			p->sched_class = next_class;
+			p->prio = newprio;
+		}
+		__setscheduler_uclamp(p, attr);
 
-		enqueue_task(rq, p, queue_flags);
+		if (scope->queued) {
+			/*
+			 * We enqueue to tail when the priority of a task is
+			 * increased (user space view).
+			 */
+			if (oldprio < p->prio)
+				scope->flags |= ENQUEUE_HEAD;
+		}
 	}
-	if (running)
-		set_next_task(rq, p);
-
-	check_class_changed(rq, p, prev_class, oldprio);
 
 	/* Avoid rq from going away on us: */
 	preempt_disable();
@@ -1351,7 +1319,7 @@ static void do_sched_yield(void)
 	rq = this_rq_lock_irq(&rf);
 
 	schedstat_inc(rq->yld_count);
-	current->sched_class->yield_task(rq);
+	rq->donor->sched_class->yield_task(rq);
 
 	preempt_disable();
 	rq_unlock_irq(rq, &rf);
@@ -1420,12 +1388,13 @@ EXPORT_SYMBOL(yield);
  */
 int __sched yield_to(struct task_struct *p, bool preempt)
 {
-	struct task_struct *curr = current;
+	struct task_struct *curr;
 	struct rq *rq, *p_rq;
 	int yielded = 0;
 
 	scoped_guard (raw_spinlock_irqsave, &p->pi_lock) {
 		rq = this_rq();
+		curr = rq->donor;
 
 again:
 		p_rq = task_rq(p);