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, 70 insertions, 72 deletions

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 275370854481..62f9278b1663 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -418,6 +418,7 @@ extern void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
 extern void sched_init_dl_servers(void);
 
 extern void fair_server_init(struct rq *rq);
+extern void ext_server_init(struct rq *rq);
 extern void __dl_server_attach_root(struct sched_dl_entity *dl_se, struct rq *rq);
 extern int dl_server_apply_params(struct sched_dl_entity *dl_se,
 		    u64 runtime, u64 period, bool init);
@@ -674,16 +675,16 @@ struct balance_callback {
 	void (*func)(struct rq *rq);
 };
 
-/* CFS-related fields in a runqueue */
+/* Fair scheduling SCHED_{NORMAL,BATCH,IDLE} related fields in a runqueue: */
 struct cfs_rq {
 	struct load_weight	load;
 	unsigned int		nr_queued;
-	unsigned int		h_nr_queued;       /* SCHED_{NORMAL,BATCH,IDLE} */
-	unsigned int		h_nr_runnable;     /* SCHED_{NORMAL,BATCH,IDLE} */
-	unsigned int		h_nr_idle; /* SCHED_IDLE */
+	unsigned int		h_nr_queued;		/* SCHED_{NORMAL,BATCH,IDLE} */
+	unsigned int		h_nr_runnable;		/* SCHED_{NORMAL,BATCH,IDLE} */
+	unsigned int		h_nr_idle;		/* SCHED_IDLE */
 
-	s64			avg_vruntime;
-	u64			avg_load;
+	s64			sum_w_vruntime;
+	u64			sum_weight;
 
 	u64			zero_vruntime;
 #ifdef CONFIG_SCHED_CORE
@@ -694,7 +695,7 @@ struct cfs_rq {
 	struct rb_root_cached	tasks_timeline;
 
 	/*
-	 * 'curr' points to currently running entity on this cfs_rq.
+	 * 'curr' points to the currently running entity on this cfs_rq.
 	 * It is set to NULL otherwise (i.e when none are currently running).
 	 */
 	struct sched_entity	*curr;
@@ -730,9 +731,7 @@ struct cfs_rq {
 	unsigned long		h_load;
 	u64			last_h_load_update;
 	struct sched_entity	*h_load_next;
-#endif /* CONFIG_FAIR_GROUP_SCHED */
 
-#ifdef CONFIG_FAIR_GROUP_SCHED
 	struct rq		*rq;	/* CPU runqueue to which this cfs_rq is attached */
 
 	/*
@@ -745,19 +744,19 @@ struct cfs_rq {
 	 */
 	int			on_list;
 	struct list_head	leaf_cfs_rq_list;
-	struct task_group	*tg;	/* group that "owns" this runqueue */
+	struct task_group	*tg;	/* Group that "owns" this runqueue */
 
 	/* Locally cached copy of our task_group's idle value */
 	int			idle;
 
-#ifdef CONFIG_CFS_BANDWIDTH
+# ifdef CONFIG_CFS_BANDWIDTH
 	int			runtime_enabled;
 	s64			runtime_remaining;
 
 	u64			throttled_pelt_idle;
-#ifndef CONFIG_64BIT
+#  ifndef CONFIG_64BIT
 	u64                     throttled_pelt_idle_copy;
-#endif
+#  endif
 	u64			throttled_clock;
 	u64			throttled_clock_pelt;
 	u64			throttled_clock_pelt_time;
@@ -769,7 +768,7 @@ struct cfs_rq {
 	struct list_head	throttled_list;
 	struct list_head	throttled_csd_list;
 	struct list_head        throttled_limbo_list;
-#endif /* CONFIG_CFS_BANDWIDTH */
+# endif /* CONFIG_CFS_BANDWIDTH */
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 };
 
@@ -1121,28 +1120,50 @@ DECLARE_STATIC_KEY_FALSE(sched_uclamp_used);
  * acquire operations must be ordered by ascending &runqueue.
  */
 struct rq {
-	/* runqueue lock: */
-	raw_spinlock_t		__lock;
-
-	/* Per class runqueue modification mask; bits in class order. */
-	unsigned int		queue_mask;
+	/*
+	 * The following members are loaded together, without holding the
+	 * rq->lock, in an extremely hot loop in update_sg_lb_stats()
+	 * (called from pick_next_task()). To reduce cache pollution from
+	 * this operation, they are placed together on this dedicated cache
+	 * line. Even though some of them are frequently modified, they are
+	 * loaded much more frequently than they are stored.
+	 */
 	unsigned int		nr_running;
 #ifdef CONFIG_NUMA_BALANCING
 	unsigned int		nr_numa_running;
 	unsigned int		nr_preferred_running;
-	unsigned int		numa_migrate_on;
 #endif
+	unsigned int		ttwu_pending;
+	unsigned long		cpu_capacity;
+#ifdef CONFIG_SCHED_PROXY_EXEC
+	struct task_struct __rcu	*donor;  /* Scheduling context */
+	struct task_struct __rcu	*curr;   /* Execution context */
+#else
+	union {
+		struct task_struct __rcu *donor; /* Scheduler context */
+		struct task_struct __rcu *curr;  /* Execution context */
+	};
+#endif
+	struct task_struct	*idle;
+	/* padding left here deliberately */
+
+	/*
+	 * The next cacheline holds the (hot) runqueue lock, as well as
+	 * some other less performance-critical fields.
+	 */
+	u64			nr_switches	____cacheline_aligned;
+
+	/* runqueue lock: */
+	raw_spinlock_t		__lock;
+
 #ifdef CONFIG_NO_HZ_COMMON
-	unsigned long		last_blocked_load_update_tick;
-	unsigned int		has_blocked_load;
-	call_single_data_t	nohz_csd;
 	unsigned int		nohz_tick_stopped;
 	atomic_t		nohz_flags;
+	unsigned int		has_blocked_load;
+	unsigned long		last_blocked_load_update_tick;
+	call_single_data_t	nohz_csd;
 #endif /* CONFIG_NO_HZ_COMMON */
 
-	unsigned int		ttwu_pending;
-	u64			nr_switches;
-
 #ifdef CONFIG_UCLAMP_TASK
 	/* Utilization clamp values based on CPU's RUNNABLE tasks */
 	struct uclamp_rq	uclamp[UCLAMP_CNT] ____cacheline_aligned;
@@ -1155,6 +1176,7 @@ struct rq {
 	struct dl_rq		dl;
 #ifdef CONFIG_SCHED_CLASS_EXT
 	struct scx_rq		scx;
+	struct sched_dl_entity	ext_server;
 #endif
 
 	struct sched_dl_entity	fair_server;
@@ -1165,6 +1187,9 @@ struct rq {
 	struct list_head	*tmp_alone_branch;
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
+#ifdef CONFIG_NUMA_BALANCING
+	unsigned int		numa_migrate_on;
+#endif
 	/*
 	 * This is part of a global counter where only the total sum
 	 * over all CPUs matters. A task can increase this counter on
@@ -1173,36 +1198,29 @@ struct rq {
 	 */
 	unsigned long		nr_uninterruptible;
 
-#ifdef CONFIG_SCHED_PROXY_EXEC
-	struct task_struct __rcu	*donor;  /* Scheduling context */
-	struct task_struct __rcu	*curr;   /* Execution context */
-#else
-	union {
-		struct task_struct __rcu *donor; /* Scheduler context */
-		struct task_struct __rcu *curr;  /* Execution context */
-	};
-#endif
 	struct sched_dl_entity	*dl_server;
-	struct task_struct	*idle;
 	struct task_struct	*stop;
+	const struct sched_class *next_class;
 	unsigned long		next_balance;
 	struct mm_struct	*prev_mm;
 
-	unsigned int		clock_update_flags;
-	u64			clock;
-	/* Ensure that all clocks are in the same cache line */
+	/*
+	 * The following fields of clock data are frequently referenced
+	 * and updated together, and should go on their own cache line.
+	 */
 	u64			clock_task ____cacheline_aligned;
 	u64			clock_pelt;
+	u64			clock;
 	unsigned long		lost_idle_time;
+	unsigned int		clock_update_flags;
 	u64			clock_pelt_idle;
 	u64			clock_idle;
+
 #ifndef CONFIG_64BIT
 	u64			clock_pelt_idle_copy;
 	u64			clock_idle_copy;
 #endif
 
-	atomic_t		nr_iowait;
-
 	u64 last_seen_need_resched_ns;
 	int ticks_without_resched;
 
@@ -1213,8 +1231,6 @@ struct rq {
 	struct root_domain		*rd;
 	struct sched_domain __rcu	*sd;
 
-	unsigned long		cpu_capacity;
-
 	struct balance_callback *balance_callback;
 
 	unsigned char		nohz_idle_balance;
@@ -1324,7 +1340,9 @@ struct rq {
 	call_single_data_t	cfsb_csd;
 	struct list_head	cfsb_csd_list;
 #endif
-};
+
+	atomic_t		nr_iowait;
+} __no_randomize_layout;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
@@ -1698,6 +1716,7 @@ static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
 
 #endif /* !CONFIG_FAIR_GROUP_SCHED */
 
+extern void update_rq_avg_idle(struct rq *rq);
 extern void update_rq_clock(struct rq *rq);
 
 /*
@@ -2062,8 +2081,8 @@ queue_balance_callback(struct rq *rq,
 	rq->balance_callback = head;
 }
 
-#define rcu_dereference_check_sched_domain(p) \
-	rcu_dereference_check((p), lockdep_is_held(&sched_domains_mutex))
+#define rcu_dereference_sched_domain(p) \
+	rcu_dereference_all_check((p), lockdep_is_held(&sched_domains_mutex))
 
 /*
  * The domain tree (rq->sd) is protected by RCU's quiescent state transition.
@@ -2073,7 +2092,7 @@ queue_balance_callback(struct rq *rq,
  * preempt-disabled sections.
  */
 #define for_each_domain(cpu, __sd) \
-	for (__sd = rcu_dereference_check_sched_domain(cpu_rq(cpu)->sd); \
+	for (__sd = rcu_dereference_sched_domain(cpu_rq(cpu)->sd); \
 			__sd; __sd = __sd->parent)
 
 /* A mask of all the SD flags that have the SDF_SHARED_CHILD metaflag */
@@ -2481,15 +2500,6 @@ struct sched_class {
 #ifdef CONFIG_UCLAMP_TASK
 	int uclamp_enabled;
 #endif
-	/*
-	 * idle:  0
-	 * ext:   1
-	 * fair:  2
-	 * rt:    4
-	 * dl:    8
-	 * stop: 16
-	 */
-	unsigned int queue_mask;
 
 	/*
 	 * move_queued_task/activate_task/enqueue_task: rq->lock
@@ -2648,20 +2658,6 @@ struct sched_class {
 #endif
 };
 
-/*
- * Does not nest; only used around sched_class::pick_task() rq-lock-breaks.
- */
-static inline void rq_modified_clear(struct rq *rq)
-{
-	rq->queue_mask = 0;
-}
-
-static inline bool rq_modified_above(struct rq *rq, const struct sched_class * class)
-{
-	unsigned int mask = class->queue_mask;
-	return rq->queue_mask & ~((mask << 1) - 1);
-}
-
 static inline void put_prev_task(struct rq *rq, struct task_struct *prev)
 {
 	WARN_ON_ONCE(rq->donor != prev);
@@ -3397,11 +3393,11 @@ struct irqtime {
 };
 
 DECLARE_PER_CPU(struct irqtime, cpu_irqtime);
-extern int sched_clock_irqtime;
+DECLARE_STATIC_KEY_FALSE(sched_clock_irqtime);
 
 static inline int irqtime_enabled(void)
 {
-	return sched_clock_irqtime;
+	return static_branch_likely(&sched_clock_irqtime);
 }
 
 /*
@@ -4010,6 +4006,7 @@ void move_queued_task_locked(struct rq *src_rq, struct rq *dst_rq, struct task_s
 	deactivate_task(src_rq, task, 0);
 	set_task_cpu(task, dst_rq->cpu);
 	activate_task(dst_rq, task, 0);
+	wakeup_preempt(dst_rq, task, 0);
 }
 
 static inline
@@ -4079,6 +4076,7 @@ extern void balance_callbacks(struct rq *rq, struct balance_callback *head);
 struct sched_change_ctx {
 	u64			prio;
 	struct task_struct	*p;
+	const struct sched_class *class;
 	int			flags;
 	bool			queued;
 	bool			running;