Merge tag 'sched-core-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:
 "Scheduler Kconfig space updates:

   - Further consolidate configurable preemption modes (Peter Zijlstra)

     Reduce the number of architectures that are allowed to offer
     PREEMPT_NONE and PREEMPT_VOLUNTARY, reducing the number of
     preemption models from four to just two: 'full' and 'lazy' on
     up-to-date architectures (arm64, loongarch, powerpc, riscv, s390,
     x86).

     None and voluntary are only available as legacy features on
     platforms that don't implement lazy preemption yet, or which don't
     even support preemption.

     The goal is to eventually remove cond_resched() and voluntary
     preemption altogether.

  RSEQ based 'scheduler time slice extension' support (Thomas Gleixner
  and Peter Zijlstra):

  This allows a thread to request a time slice extension when it enters
  a critical section to avoid contention on a resource when the thread
  is scheduled out inside of the critical section.

   - Add fields and constants for time slice extension
   - Provide static branch for time slice extensions
   - Add statistics for time slice extensions
   - Add prctl() to enable time slice extensions
   - Implement sys_rseq_slice_yield()
   - Implement syscall entry work for time slice extensions
   - Implement time slice extension enforcement timer
   - Reset slice extension when scheduled
   - Implement rseq_grant_slice_extension()
   - entry: Hook up rseq time slice extension
   - selftests: Implement time slice extension test
   - Allow registering RSEQ with slice extension
   - Move slice_ext_nsec to debugfs
   - Lower default slice extension
   - selftests/rseq: Add rseq slice histogram script

  Scheduler performance/scalability improvements:

   - Update rq->avg_idle when a task is moved to an idle CPU, which
     improves the scalability of various workloads (Shubhang Kaushik)

   - Reorder fields in 'struct rq' for better caching (Blake Jones)

   - Fair scheduler SMP NOHZ balancing code speedups (Shrikanth Hegde):
      - Move checking for nohz cpus after time check
      - Change likelyhood of nohz.nr_cpus
      - Remove nohz.nr_cpus and use weight of cpumask instead

   - Avoid false sharing for sched_clock_irqtime (Wangyang Guo)

   - Cleanups (Yury Norov):
      - Drop useless cpumask_empty() in find_energy_efficient_cpu()
      - Simplify task_numa_find_cpu()
      - Use cpumask_weight_and() in sched_balance_find_dst_group()

  DL scheduler updates:

   - Add a deadline server for sched_ext tasks (by Andrea Righi and Joel
     Fernandes, with fixes by Peter Zijlstra)

  RT scheduler updates:

   - Skip currently executing CPU in rto_next_cpu() (Chen Jinghuang)

  Entry code updates and performance improvements (Jinjie Ruan)

  This is part of the scheduler tree in this cycle due to inter-
  dependencies with the RSEQ based time slice extension work:

    - Remove unused syscall argument from syscall_trace_enter()
    - Rework syscall_exit_to_user_mode_work() for architecture reuse
    - Add arch_ptrace_report_syscall_entry/exit()
    - Inline syscall_exit_work() and syscall_trace_enter()

  Scheduler core updates (Peter Zijlstra):

   - Rework sched_class::wakeup_preempt() and rq_modified_*()
   - Avoid rq->lock bouncing in sched_balance_newidle()
   - Rename rcu_dereference_check_sched_domain() =>
            rcu_dereference_sched_domain()
   - <linux/compiler_types.h>: Add the __signed_scalar_typeof() helper

  Fair scheduler updates/refactoring (Peter Zijlstra and Ingo Molnar):

   - Fold the sched_avg update
   - Change rcu_dereference_check_sched_domain() to rcu-sched
   - Switch to rcu_dereference_all()
   - Remove superfluous rcu_read_lock()
   - Limit hrtick work
   - Join two #ifdef CONFIG_FAIR_GROUP_SCHED blocks
   - Clean up comments in 'struct cfs_rq'
   - Separate se->vlag from se->vprot
   - Rename cfs_rq::avg_load to cfs_rq::sum_weight
   - Rename cfs_rq::avg_vruntime to ::sum_w_vruntime & helper functions
   - Introduce and use the vruntime_cmp() and vruntime_op() wrappers for
     wrapped-signed aritmetics
   - Sort out 'blocked_load*' namespace noise

  Scheduler debugging code updates:

   - Export hidden tracepoints to modules (Gabriele Monaco)

   - Convert copy_from_user() + kstrtouint() to kstrtouint_from_user()
     (Fushuai Wang)

   - Add assertions to QUEUE_CLASS (Peter Zijlstra)

   - hrtimer: Fix tracing oddity (Thomas Gleixner)

  Misc fixes and cleanups:

   - Re-evaluate scheduling when migrating queued tasks out of throttled
     cgroups (Zicheng Qu)

   - Remove task_struct->faults_disabled_mapping (Christoph Hellwig)

   - Fix math notation errors in avg_vruntime comment (Zhan Xusheng)

   - sched/cpufreq: Use %pe format for PTR_ERR() printing
     (zenghongling)"

* tag 'sched-core-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits)
  sched: Re-evaluate scheduling when migrating queued tasks out of throttled cgroups
  sched/cpufreq: Use %pe format for PTR_ERR() printing
  sched/rt: Skip currently executing CPU in rto_next_cpu()
  sched/clock: Avoid false sharing for sched_clock_irqtime
  selftests/sched_ext: Add test for DL server total_bw consistency
  selftests/sched_ext: Add test for sched_ext dl_server
  sched/debug: Fix dl_server (re)start conditions
  sched/debug: Add support to change sched_ext server params
  sched_ext: Add a DL server for sched_ext tasks
  sched/debug: Stop and start server based on if it was active
  sched/debug: Fix updating of ppos on server write ops
  sched/deadline: Clear the defer params
  entry: Inline syscall_exit_work() and syscall_trace_enter()
  entry: Add arch_ptrace_report_syscall_entry/exit()
  entry: Rework syscall_exit_to_user_mode_work() for architecture reuse
  entry: Remove unused syscall argument from syscall_trace_enter()
  sched: remove task_struct->faults_disabled_mapping
  sched: Update rq->avg_idle when a task is moved to an idle CPU
  selftests/rseq: Add rseq slice histogram script
  hrtimer: Fix trace oddity
  ...

1 files changed, 64 insertions, 22 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d78d7b6d30bb..23406f037dde 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -119,6 +119,9 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(sched_entry_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(sched_exit_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(sched_set_need_resched_tp);
 
 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 DEFINE_PER_CPU(struct rnd_state, sched_rnd_state);
@@ -1141,6 +1144,7 @@ void __trace_set_need_resched(struct task_struct *curr, int tif)
 {
 	trace_sched_set_need_resched_tp(curr, smp_processor_id(), tif);
 }
+EXPORT_SYMBOL_GPL(__trace_set_need_resched);
 
 void resched_curr(struct rq *rq)
 {
@@ -2095,7 +2099,6 @@ void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
 	 */
 	uclamp_rq_inc(rq, p, flags);
 
-	rq->queue_mask |= p->sched_class->queue_mask;
 	p->sched_class->enqueue_task(rq, p, flags);
 
 	psi_enqueue(p, flags);
@@ -2128,7 +2131,6 @@ inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags)
 	 * and mark the task ->sched_delayed.
 	 */
 	uclamp_rq_dec(rq, p);
-	rq->queue_mask |= p->sched_class->queue_mask;
 	return p->sched_class->dequeue_task(rq, p, flags);
 }
 
@@ -2179,10 +2181,14 @@ void wakeup_preempt(struct rq *rq, struct task_struct *p, int flags)
 {
 	struct task_struct *donor = rq->donor;
 
-	if (p->sched_class == donor->sched_class)
-		donor->sched_class->wakeup_preempt(rq, p, flags);
-	else if (sched_class_above(p->sched_class, donor->sched_class))
+	if (p->sched_class == rq->next_class) {
+		rq->next_class->wakeup_preempt(rq, p, flags);
+
+	} else if (sched_class_above(p->sched_class, rq->next_class)) {
+		rq->next_class->wakeup_preempt(rq, p, flags);
 		resched_curr(rq);
+		rq->next_class = p->sched_class;
+	}
 
 	/*
 	 * A queue event has occurred, and we're going to schedule.  In
@@ -3620,6 +3626,18 @@ static inline void ttwu_do_wakeup(struct task_struct *p)
 	trace_sched_wakeup(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;
+
+	update_avg(&rq->avg_idle, delta);
+
+	if (rq->avg_idle > max)
+		rq->avg_idle = max;
+	rq->idle_stamp = 0;
+}
+
 static void
 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
 		 struct rq_flags *rf)
@@ -3655,18 +3673,6 @@ ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
 		p->sched_class->task_woken(rq, p);
 		rq_repin_lock(rq, rf);
 	}
-
-	if (rq->idle_stamp) {
-		u64 delta = rq_clock(rq) - rq->idle_stamp;
-		u64 max = 2*rq->max_idle_balance_cost;
-
-		update_avg(&rq->avg_idle, delta);
-
-		if (rq->avg_idle > max)
-			rq->avg_idle = max;
-
-		rq->idle_stamp = 0;
-	}
 }
 
 /*
@@ -6836,6 +6842,7 @@ static void __sched notrace __schedule(int sched_mode)
 pick_again:
 	next = pick_next_task(rq, rq->donor, &rf);
 	rq_set_donor(rq, next);
+	rq->next_class = next->sched_class;
 	if (unlikely(task_is_blocked(next))) {
 		next = find_proxy_task(rq, next, &rf);
 		if (!next)
@@ -7580,7 +7587,7 @@ int preempt_dynamic_mode = preempt_dynamic_undefined;
 
 int sched_dynamic_mode(const char *str)
 {
-# ifndef CONFIG_PREEMPT_RT
+# if !(defined(CONFIG_PREEMPT_RT) || defined(CONFIG_ARCH_HAS_PREEMPT_LAZY))
 	if (!strcmp(str, "none"))
 		return preempt_dynamic_none;
 
@@ -8512,6 +8519,9 @@ int sched_cpu_dying(unsigned int cpu)
 		dump_rq_tasks(rq, KERN_WARNING);
 	}
 	dl_server_stop(&rq->fair_server);
+#ifdef CONFIG_SCHED_CLASS_EXT
+	dl_server_stop(&rq->ext_server);
+#endif
 	rq_unlock_irqrestore(rq, &rf);
 
 	calc_load_migrate(rq);
@@ -8687,6 +8697,8 @@ void __init sched_init(void)
 		rq->rt.rt_runtime = global_rt_runtime();
 		init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
 #endif
+		rq->next_class = &idle_sched_class;
+
 		rq->sd = NULL;
 		rq->rd = NULL;
 		rq->cpu_capacity = SCHED_CAPACITY_SCALE;
@@ -8715,6 +8727,9 @@ void __init sched_init(void)
 		hrtick_rq_init(rq);
 		atomic_set(&rq->nr_iowait, 0);
 		fair_server_init(rq);
+#ifdef CONFIG_SCHED_CLASS_EXT
+		ext_server_init(rq);
+#endif
 
 #ifdef CONFIG_SCHED_CORE
 		rq->core = rq;
@@ -9146,6 +9161,7 @@ void sched_move_task(struct task_struct *tsk, bool for_autogroup)
 {
 	unsigned int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE;
 	bool resched = false;
+	bool queued = false;
 	struct rq *rq;
 
 	CLASS(task_rq_lock, rq_guard)(tsk);
@@ -9157,10 +9173,13 @@ void sched_move_task(struct task_struct *tsk, bool for_autogroup)
 			scx_cgroup_move_task(tsk);
 		if (scope->running)
 			resched = true;
+		queued = scope->queued;
 	}
 
 	if (resched)
 		resched_curr(rq);
+	else if (queued)
+		wakeup_preempt(rq, tsk, 0);
 
 	__balance_callbacks(rq, &rq_guard.rf);
 }
@@ -10883,13 +10902,12 @@ struct sched_change_ctx *sched_change_begin(struct task_struct *p, unsigned int
 		flags |= DEQUEUE_NOCLOCK;
 	}
 
-	if (flags & DEQUEUE_CLASS) {
-		if (p->sched_class->switching_from)
-			p->sched_class->switching_from(rq, p);
-	}
+	if ((flags & DEQUEUE_CLASS) && p->sched_class->switching_from)
+		p->sched_class->switching_from(rq, p);
 
 	*ctx = (struct sched_change_ctx){
 		.p = p,
+		.class = p->sched_class,
 		.flags = flags,
 		.queued = task_on_rq_queued(p),
 		.running = task_current_donor(rq, p),
@@ -10920,6 +10938,11 @@ void sched_change_end(struct sched_change_ctx *ctx)
 
 	lockdep_assert_rq_held(rq);
 
+	/*
+	 * Changing class without *QUEUE_CLASS is bad.
+	 */
+	WARN_ON_ONCE(p->sched_class != ctx->class && !(ctx->flags & ENQUEUE_CLASS));
+
 	if ((ctx->flags & ENQUEUE_CLASS) && p->sched_class->switching_to)
 		p->sched_class->switching_to(rq, p);
 
@@ -10931,6 +10954,25 @@ void sched_change_end(struct sched_change_ctx *ctx)
 	if (ctx->flags & ENQUEUE_CLASS) {
 		if (p->sched_class->switched_to)
 			p->sched_class->switched_to(rq, p);
+
+		if (ctx->running) {
+			/*
+			 * If this was a class promotion; let the old class
+			 * know it got preempted. Note that none of the
+			 * switch*_from() methods know the new class and none
+			 * of the switch*_to() methods know the old class.
+			 */
+			if (sched_class_above(p->sched_class, ctx->class)) {
+				rq->next_class->wakeup_preempt(rq, p, 0);
+				rq->next_class = p->sched_class;
+			}
+			/*
+			 * If this was a degradation in class; make sure to
+			 * reschedule.
+			 */
+			if (sched_class_above(ctx->class, p->sched_class))
+				resched_curr(rq);
+		}
 	} else {
 		p->sched_class->prio_changed(rq, p, ctx->prio);
 	}