Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:
 "The main scheduler changes in this cycle were:

   - NUMA balancing improvements (Mel Gorman)

   - Further load tracking improvements (Patrick Bellasi)

   - Various NOHZ balancing cleanups and optimizations (Peter Zijlstra)

   - Improve blocked load handling, in particular we can now reduce and
     eventually stop periodic load updates on 'very idle' CPUs. (Vincent
     Guittot)

   - On isolated CPUs offload the final 1Hz scheduler tick as well, plus
     related cleanups and reorganization. (Frederic Weisbecker)

   - Core scheduler code cleanups (Ingo Molnar)"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (45 commits)
  sched/core: Update preempt_notifier_key to modern API
  sched/cpufreq: Rate limits for SCHED_DEADLINE
  sched/fair: Update util_est only on util_avg updates
  sched/cpufreq/schedutil: Use util_est for OPP selection
  sched/fair: Use util_est in LB and WU paths
  sched/fair: Add util_est on top of PELT
  sched/core: Remove TASK_ALL
  sched/completions: Use bool in try_wait_for_completion()
  sched/fair: Update blocked load when newly idle
  sched/fair: Move idle_balance()
  sched/nohz: Merge CONFIG_NO_HZ_COMMON blocks
  sched/fair: Move rebalance_domains()
  sched/nohz: Optimize nohz_idle_balance()
  sched/fair: Reduce the periodic update duration
  sched/nohz: Stop NOHZ stats when decayed
  sched/cpufreq: Provide migration hint
  sched/nohz: Clean up nohz enter/exit
  sched/fair: Update blocked load from NEWIDLE
  sched/fair: Add NOHZ stats balancing
  sched/fair: Restructure nohz_balance_kick()
  ...

Documentation/admin-guide/kernel-parameters.txt

@@ -1766,6 +1766,17 @@
 
 			nohz
 			  Disable the tick when a single task runs.
+
+			  A residual 1Hz tick is offloaded to workqueues, which you
+			  need to affine to housekeeping through the global
+			  workqueue's affinity configured via the
+			  /sys/devices/virtual/workqueue/cpumask sysfs file, or
+			  by using the 'domain' flag described below.
+
+			  NOTE: by default the global workqueue runs on all CPUs,
+			  so to protect individual CPUs the 'cpumask' file has to
+			  be configured manually after bootup.
+
 			domain
 			  Isolate from the general SMP balancing and scheduling
 			  algorithms. Note that performing domain isolation this way

include/linux/sched.h

@@ -93,7 +93,6 @@ struct task_group;
 
 /* Convenience macros for the sake of wake_up(): */
 #define TASK_NORMAL			(TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE)
-#define TASK_ALL			(TASK_NORMAL | __TASK_STOPPED | __TASK_TRACED)
 
 /* get_task_state(): */
 #define TASK_REPORT			(TASK_RUNNING | TASK_INTERRUPTIBLE | \
@@ -275,6 +274,34 @@ struct load_weight {
 	u32				inv_weight;
 };
 
+/**
+ * struct util_est - Estimation utilization of FAIR tasks
+ * @enqueued: instantaneous estimated utilization of a task/cpu
+ * @ewma:     the Exponential Weighted Moving Average (EWMA)
+ *            utilization of a task
+ *
+ * Support data structure to track an Exponential Weighted Moving Average
+ * (EWMA) of a FAIR task's utilization. New samples are added to the moving
+ * average each time a task completes an activation. Sample's weight is chosen
+ * so that the EWMA will be relatively insensitive to transient changes to the
+ * task's workload.
+ *
+ * The enqueued attribute has a slightly different meaning for tasks and cpus:
+ * - task:   the task's util_avg at last task dequeue time
+ * - cfs_rq: the sum of util_est.enqueued for each RUNNABLE task on that CPU
+ * Thus, the util_est.enqueued of a task represents the contribution on the
+ * estimated utilization of the CPU where that task is currently enqueued.
+ *
+ * Only for tasks we track a moving average of the past instantaneous
+ * estimated utilization. This allows to absorb sporadic drops in utilization
+ * of an otherwise almost periodic task.
+ */
+struct util_est {
+	unsigned int			enqueued;
+	unsigned int			ewma;
+#define UTIL_EST_WEIGHT_SHIFT		2
+};
+
 /*
  * The load_avg/util_avg accumulates an infinite geometric series
  * (see __update_load_avg() in kernel/sched/fair.c).
@@ -336,6 +363,7 @@ struct sched_avg {
 	unsigned long			load_avg;
 	unsigned long			runnable_load_avg;
 	unsigned long			util_avg;
+	struct util_est			util_est;
 };
 
 struct sched_statistics {

include/linux/sched/cpufreq.h

@@ -8,9 +8,8 @@
  * Interface between cpufreq drivers and the scheduler:
  */
 
-#define SCHED_CPUFREQ_RT	(1U << 0)
-#define SCHED_CPUFREQ_DL	(1U << 1)
-#define SCHED_CPUFREQ_IOWAIT	(1U << 2)
+#define SCHED_CPUFREQ_IOWAIT	(1U << 0)
+#define SCHED_CPUFREQ_MIGRATION	(1U << 1)
 
 #ifdef CONFIG_CPU_FREQ
 struct update_util_data {

include/linux/sched/deadline.h

 /* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _LINUX_SCHED_DEADLINE_H
-#define _LINUX_SCHED_DEADLINE_H
-
-#include <linux/sched.h>
 
 /*
  * SCHED_DEADLINE tasks has negative priorities, reflecting
@@ -28,5 +24,3 @@ static inline bool dl_time_before(u64 a, u64 b)
 {
 	return (s64)(a - b) < 0;
 }
-
-#endif /* _LINUX_SCHED_DEADLINE_H */

include/linux/sched/isolation.h

@@ -12,6 +12,7 @@ enum hk_flags {
 	HK_FLAG_SCHED		= (1 << 3),
 	HK_FLAG_TICK		= (1 << 4),
 	HK_FLAG_DOMAIN		= (1 << 5),
+	HK_FLAG_WQ		= (1 << 6),
 };
 
 #ifdef CONFIG_CPU_ISOLATION

include/linux/sched/nohz.h

@@ -16,11 +16,9 @@ static inline void cpu_load_update_nohz_stop(void) { }
 
 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
 extern void nohz_balance_enter_idle(int cpu);
-extern void set_cpu_sd_state_idle(void);
 extern int get_nohz_timer_target(void);
 #else
 static inline void nohz_balance_enter_idle(int cpu) { }
-static inline void set_cpu_sd_state_idle(void) { }
 #endif
 
 #ifdef CONFIG_NO_HZ_COMMON
@@ -37,8 +35,4 @@ extern void wake_up_nohz_cpu(int cpu);
 static inline void wake_up_nohz_cpu(int cpu) { }
 #endif
 
-#ifdef CONFIG_NO_HZ_FULL
-extern u64 scheduler_tick_max_deferment(void);
-#endif
-
 #endif /* _LINUX_SCHED_NOHZ_H */

include/linux/tick.h

@@ -113,7 +113,8 @@ enum tick_dep_bits {
 
 #ifdef CONFIG_NO_HZ_COMMON
 extern bool tick_nohz_enabled;
-extern int tick_nohz_tick_stopped(void);
+extern bool tick_nohz_tick_stopped(void);
+extern bool tick_nohz_tick_stopped_cpu(int cpu);
 extern void tick_nohz_idle_enter(void);
 extern void tick_nohz_idle_exit(void);
 extern void tick_nohz_irq_exit(void);
@@ -125,6 +126,7 @@ extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
 #else /* !CONFIG_NO_HZ_COMMON */
 #define tick_nohz_enabled (0)
 static inline int tick_nohz_tick_stopped(void) { return 0; }
+static inline int tick_nohz_tick_stopped_cpu(int cpu) { return 0; }
 static inline void tick_nohz_idle_enter(void) { }
 static inline void tick_nohz_idle_exit(void) { }
 

kernel/sched/Makefile

@@ -17,8 +17,9 @@ CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
 endif
 
 obj-y += core.o loadavg.o clock.o cputime.o
-obj-y += idle_task.o fair.o rt.o deadline.o
-obj-y += wait.o wait_bit.o swait.o completion.o idle.o
+obj-y += idle.o fair.o rt.o deadline.o
+obj-y += wait.o wait_bit.o swait.o completion.o
+
 obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o topology.o stop_task.o
 obj-$(CONFIG_SCHED_AUTOGROUP) += autogroup.o
 obj-$(CONFIG_SCHEDSTATS) += stats.o

kernel/sched/autogroup.c

 // SPDX-License-Identifier: GPL-2.0
-#include <linux/proc_fs.h>
-#include <linux/seq_file.h>
-#include <linux/utsname.h>
-#include <linux/security.h>
-#include <linux/export.h>
-
+/*
+ * Auto-group scheduling implementation:
+ */
 #include "sched.h"
 
 unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
@@ -168,18 +165,19 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 	autogroup_kref_put(prev);
 }
 
-/* Allocates GFP_KERNEL, cannot be called under any spinlock */
+/* Allocates GFP_KERNEL, cannot be called under any spinlock: */
 void sched_autogroup_create_attach(struct task_struct *p)
 {
 	struct autogroup *ag = autogroup_create();
 
 	autogroup_move_group(p, ag);
-	/* drop extra reference added by autogroup_create() */
+
+	/* Drop extra reference added by autogroup_create(): */
 	autogroup_kref_put(ag);
 }
 EXPORT_SYMBOL(sched_autogroup_create_attach);
 
-/* Cannot be called under siglock.  Currently has no users */
+/* Cannot be called under siglock. Currently has no users: */
 void sched_autogroup_detach(struct task_struct *p)
 {
 	autogroup_move_group(p, &autogroup_default);
@@ -202,7 +200,6 @@ static int __init setup_autogroup(char *str)
 
 	return 1;
 }
-
 __setup("noautogroup", setup_autogroup);
 
 #ifdef CONFIG_PROC_FS
@@ -224,7 +221,7 @@ int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
 	if (nice < 0 && !can_nice(current, nice))
 		return -EPERM;
 
-	/* this is a heavy operation taking global locks.. */
+	/* This is a heavy operation, taking global locks.. */
 	if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
 		return -EAGAIN;
 
@@ -267,4 +264,4 @@ int autogroup_path(struct task_group *tg, char *buf, int buflen)
 
 	return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
 }
-#endif /* CONFIG_SCHED_DEBUG */
+#endif

kernel/sched/autogroup.h

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifdef CONFIG_SCHED_AUTOGROUP
 
-#include <linux/kref.h>
-#include <linux/rwsem.h>
-#include <linux/sched/autogroup.h>
-
 struct autogroup {
 	/*
-	 * reference doesn't mean how many thread attach to this
-	 * autogroup now. It just stands for the number of task
-	 * could use this autogroup.
+	 * Reference doesn't mean how many threads attach to this
+	 * autogroup now. It just stands for the number of tasks
+	 * which could use this autogroup.
 	 */
 	struct kref		kref;
 	struct task_group	*tg;
@@ -56,11 +52,9 @@ autogroup_task_group(struct task_struct *p, struct task_group *tg)
 	return tg;
 }
 
-#ifdef CONFIG_SCHED_DEBUG
 static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
 {
 	return 0;
 }
-#endif
 
 #endif /* CONFIG_SCHED_AUTOGROUP */

kernel/sched/clock.c

 /*
- * sched_clock for unstable cpu clocks
+ * sched_clock() for unstable CPU clocks
  *
  *  Copyright (C) 2008 Red Hat, Inc., Peter Zijlstra
  *
@@ -11,7 +11,7 @@
  *   Guillaume Chazarain <guichaz@gmail.com>
  *
  *
- * What:
+ * What this file implements:
  *
  * cpu_clock(i) provides a fast (execution time) high resolution
  * clock with bounded drift between CPUs. The value of cpu_clock(i)
@@ -26,11 +26,11 @@
  * at 0 on boot (but people really shouldn't rely on that).
  *
  * cpu_clock(i)       -- can be used from any context, including NMI.
- * local_clock()      -- is cpu_clock() on the current cpu.
+ * local_clock()      -- is cpu_clock() on the current CPU.
  *
  * sched_clock_cpu(i)
  *
- * How:
+ * How it is implemented:
  *
  * The implementation either uses sched_clock() when
  * !CONFIG_HAVE_UNSTABLE_SCHED_CLOCK, which means in that case the
@@ -52,19 +52,7 @@
  * that is otherwise invisible (TSC gets stopped).
  *
  */
-#include <linux/spinlock.h>
-#include <linux/hardirq.h>
-#include <linux/export.h>
-#include <linux/percpu.h>
-#include <linux/ktime.h>
-#include <linux/sched.h>
-#include <linux/nmi.h>
-#include <linux/sched/clock.h>
-#include <linux/static_key.h>
-#include <linux/workqueue.h>
-#include <linux/compiler.h>
-#include <linux/tick.h>
-#include <linux/init.h>
+#include "sched.h"
 
 /*
  * Scheduler clock - returns current time in nanosec units.
@@ -302,21 +290,21 @@ static u64 sched_clock_remote(struct sched_clock_data *scd)
 	 * cmpxchg64 below only protects one readout.
 	 *
 	 * We must reread via sched_clock_local() in the retry case on
-	 * 32bit as an NMI could use sched_clock_local() via the
+	 * 32-bit kernels as an NMI could use sched_clock_local() via the
 	 * tracer and hit between the readout of
-	 * the low32bit and the high 32bit portion.
+	 * the low 32-bit and the high 32-bit portion.
 	 */
 	this_clock = sched_clock_local(my_scd);
 	/*
-	 * We must enforce atomic readout on 32bit, otherwise the
-	 * update on the remote cpu can hit inbetween the readout of
-	 * the low32bit and the high 32bit portion.
+	 * We must enforce atomic readout on 32-bit, otherwise the
+	 * update on the remote CPU can hit inbetween the readout of
+	 * the low 32-bit and the high 32-bit portion.
 	 */
 	remote_clock = cmpxchg64(&scd->clock, 0, 0);
 #else
 	/*
-	 * On 64bit the read of [my]scd->clock is atomic versus the
-	 * update, so we can avoid the above 32bit dance.
+	 * On 64-bit kernels the read of [my]scd->clock is atomic versus the
+	 * update, so we can avoid the above 32-bit dance.
 	 */
 	sched_clock_local(my_scd);
 again:

kernel/sched/completion.c

@@ -11,10 +11,7 @@
  * typically be used for exclusion which gives rise to priority inversion.
  * Waiting for completion is a typically sync point, but not an exclusion point.
  */
-
-#include <linux/sched/signal.h>
-#include <linux/sched/debug.h>
-#include <linux/completion.h>
+#include "sched.h"
 
 /**
  * complete: - signals a single thread waiting on this completion
@@ -283,7 +280,7 @@ EXPORT_SYMBOL(wait_for_completion_killable_timeout);
 bool try_wait_for_completion(struct completion *x)
 {
 	unsigned long flags;
-	int ret = 1;
+	bool ret = true;
 
 	/*
 	 * Since x->done will need to be locked only
@@ -292,11 +289,11 @@ bool try_wait_for_completion(struct completion *x)
 	 * return early in the blocking case.
 	 */
 	if (!READ_ONCE(x->done))
-		return 0;
+		return false;
 
 	spin_lock_irqsave(&x->wait.lock, flags);
 	if (!x->done)
-		ret = 0;
+		ret = false;
 	else if (x->done != UINT_MAX)
 		x->done--;
 	spin_unlock_irqrestore(&x->wait.lock, flags);

kernel/sched/core.c

@@ -5,37 +5,11 @@
  *
  *  Copyright (C) 1991-2002  Linus Torvalds
  */
-#include <linux/sched.h>
-#include <linux/sched/clock.h>
-#include <uapi/linux/sched/types.h>
-#include <linux/sched/loadavg.h>
-#include <linux/sched/hotplug.h>
-#include <linux/wait_bit.h>
-#include <linux/cpuset.h>
-#include <linux/delayacct.h>
-#include <linux/init_task.h>
-#include <linux/context_tracking.h>
-#include <linux/rcupdate_wait.h>
-#include <linux/compat.h>
-
-#include <linux/blkdev.h>
-#include <linux/kprobes.h>
-#include <linux/mmu_context.h>
-#include <linux/module.h>
-#include <linux/nmi.h>
-#include <linux/prefetch.h>
-#include <linux/profile.h>
-#include <linux/security.h>
-#include <linux/syscalls.h>
-#include <linux/sched/isolation.h>
+#include "sched.h"
 
 #include <asm/switch_to.h>
 #include <asm/tlb.h>
-#ifdef CONFIG_PARAVIRT
-#include <asm/paravirt.h>
-#endif
 
-#include "sched.h"
 #include "../workqueue_internal.h"
 #include "../smpboot.h"
 
@@ -135,7 +109,7 @@ struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
 		 *					[L] ->on_rq
 		 *	RELEASE (rq->lock)
 		 *
-		 * If we observe the old cpu in task_rq_lock, the acquire of
+		 * If we observe the old CPU in task_rq_lock, the acquire of
 		 * the old rq->lock will fully serialize against the stores.
 		 *
 		 * If we observe the new CPU in task_rq_lock, the acquire will
@@ -333,7 +307,7 @@ void hrtick_start(struct rq *rq, u64 delay)
 }
 #endif /* CONFIG_SMP */
 
-static void init_rq_hrtick(struct rq *rq)
+static void hrtick_rq_init(struct rq *rq)
 {
 #ifdef CONFIG_SMP
 	rq->hrtick_csd_pending = 0;
@@ -351,7 +325,7 @@ static inline void hrtick_clear(struct rq *rq)
 {
 }
 
-static inline void init_rq_hrtick(struct rq *rq)
+static inline void hrtick_rq_init(struct rq *rq)
 {
 }
 #endif	/* CONFIG_SCHED_HRTICK */
@@ -609,7 +583,7 @@ static inline bool got_nohz_idle_kick(void)
 {
 	int cpu = smp_processor_id();
 
-	if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)))
+	if (!(atomic_read(nohz_flags(cpu)) & NOHZ_KICK_MASK))
 		return false;
 
 	if (idle_cpu(cpu) && !need_resched())
@@ -619,7 +593,7 @@ static inline bool got_nohz_idle_kick(void)
 	 * We can't run Idle Load Balance on this CPU for this time so we
 	 * cancel it and clear NOHZ_BALANCE_KICK
 	 */
-	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
+	atomic_andnot(NOHZ_KICK_MASK, nohz_flags(cpu));
 	return false;
 }
 
@@ -1457,7 +1431,7 @@ EXPORT_SYMBOL_GPL(kick_process);
  *
  *  - cpu_active must be a subset of cpu_online
  *
- *  - on cpu-up we allow per-cpu kthreads on the online && !active cpu,
+ *  - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
  *    see __set_cpus_allowed_ptr(). At this point the newly online
  *    CPU isn't yet part of the sched domains, and balancing will not
  *    see it.
@@ -2488,17 +2462,17 @@ void wake_up_new_task(struct task_struct *p)
 
 #ifdef CONFIG_PREEMPT_NOTIFIERS
 
-static struct static_key preempt_notifier_key = STATIC_KEY_INIT_FALSE;
+static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
 
 void preempt_notifier_inc(void)
 {
-	static_key_slow_inc(&preempt_notifier_key);
+	static_branch_inc(&preempt_notifier_key);
 }
 EXPORT_SYMBOL_GPL(preempt_notifier_inc);
 
 void preempt_notifier_dec(void)
 {
-	static_key_slow_dec(&preempt_notifier_key);
+	static_branch_dec(&preempt_notifier_key);
 }
 EXPORT_SYMBOL_GPL(preempt_notifier_dec);
 
@@ -2508,7 +2482,7 @@ EXPORT_SYMBOL_GPL(preempt_notifier_dec);
  */
 void preempt_notifier_register(struct preempt_notifier *notifier)
 {
-	if (!static_key_false(&preempt_notifier_key))
+	if (!static_branch_unlikely(&preempt_notifier_key))
 		WARN(1, "registering preempt_notifier while notifiers disabled\n");
 
 	hlist_add_head(&notifier->link, &current->preempt_notifiers);
@@ -2537,7 +2511,7 @@ static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
 
 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
 {
-	if (static_key_false(&preempt_notifier_key))
+	if (static_branch_unlikely(&preempt_notifier_key))
 		__fire_sched_in_preempt_notifiers(curr);
 }
 
@@ -2555,7 +2529,7 @@ static __always_inline void
 fire_sched_out_preempt_notifiers(struct task_struct *curr,
 				 struct task_struct *next)
 {
-	if (static_key_false(&preempt_notifier_key))
+	if (static_branch_unlikely(&preempt_notifier_key))
 		__fire_sched_out_preempt_notifiers(curr, next);
 }
 
@@ -2629,6 +2603,18 @@ static inline void finish_lock_switch(struct rq *rq)
 	raw_spin_unlock_irq(&rq->lock);
 }
 
+/*
+ * NOP if the arch has not defined these:
+ */
+
+#ifndef prepare_arch_switch
+# define prepare_arch_switch(next)	do { } while (0)
+#endif
+
+#ifndef finish_arch_post_lock_switch
+# define finish_arch_post_lock_switch()	do { } while (0)
+#endif
+
 /**
  * prepare_task_switch - prepare to switch tasks
  * @rq: the runqueue preparing to switch
@@ -3037,7 +3023,7 @@ unsigned long long task_sched_runtime(struct task_struct *p)
 
 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
 	/*
-	 * 64-bit doesn't need locks to atomically read a 64bit value.
+	 * 64-bit doesn't need locks to atomically read a 64-bit value.
 	 * So we have a optimization chance when the task's delta_exec is 0.
 	 * Reading ->on_cpu is racy, but this is ok.
 	 *
@@ -3096,35 +3082,99 @@ void scheduler_tick(void)
 	rq->idle_balance = idle_cpu(cpu);
 	trigger_load_balance(rq);
 #endif
-	rq_last_tick_reset(rq);
 }
 
 #ifdef CONFIG_NO_HZ_FULL
-/**
- * scheduler_tick_max_deferment
- *
- * Keep at least one tick per second when a single
- * active task is running because the scheduler doesn't
- * yet completely support full dynticks environment.
- *
- * This makes sure that uptime, CFS vruntime, load
- * balancing, etc... continue to move forward, even
- * with a very low granularity.
- *
- * Return: Maximum deferment in nanoseconds.
- */
-u64 scheduler_tick_max_deferment(void)
+
+struct tick_work {
+	int			cpu;
+	struct delayed_work	work;
+};
+
+static struct tick_work __percpu *tick_work_cpu;
+
+static void sched_tick_remote(struct work_struct *work)
 {
-	struct rq *rq = this_rq();
-	unsigned long next, now = READ_ONCE(jiffies);
+	struct delayed_work *dwork = to_delayed_work(work);
+	struct tick_work *twork = container_of(dwork, struct tick_work, work);
+	int cpu = twork->cpu;
+	struct rq *rq = cpu_rq(cpu);
+	struct rq_flags rf;
 
-	next = rq->last_sched_tick + HZ;
+	/*
+	 * Handle the tick only if it appears the remote CPU is running in full
+	 * dynticks mode. The check is racy by nature, but missing a tick or
+	 * having one too much is no big deal because the scheduler tick updates
+	 * statistics and checks timeslices in a time-independent way, regardless
+	 * of when exactly it is running.
+	 */
+	if (!idle_cpu(cpu) && tick_nohz_tick_stopped_cpu(cpu)) {
+		struct task_struct *curr;
+		u64 delta;
 
-	if (time_before_eq(next, now))
-		return 0;
+		rq_lock_irq(rq, &rf);
+		update_rq_clock(rq);
+		curr = rq->curr;
+		delta = rq_clock_task(rq) - curr->se.exec_start;
 
-	return jiffies_to_nsecs(next - now);
+		/*
+		 * Make sure the next tick runs within a reasonable
+		 * amount of time.
+		 */
+		WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
+		curr->sched_class->task_tick(rq, curr, 0);
+		rq_unlock_irq(rq, &rf);
+	}
+
+	/*
+	 * Run the remote tick once per second (1Hz). This arbitrary
+	 * frequency is large enough to avoid overload but short enough
+	 * to keep scheduler internal stats reasonably up to date.
+	 */
+	queue_delayed_work(system_unbound_wq, dwork, HZ);
 }
+
+static void sched_tick_start(int cpu)
+{
+	struct tick_work *twork;
+
+	if (housekeeping_cpu(cpu, HK_FLAG_TICK))
+		return;
+
+	WARN_ON_ONCE(!tick_work_cpu);
+
+	twork = per_cpu_ptr(tick_work_cpu, cpu);
+	twork->cpu = cpu;
+	INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
+	queue_delayed_work(system_unbound_wq, &twork->work, HZ);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void sched_tick_stop(int cpu)
+{
+	struct tick_work *twork;
+
+	if (housekeeping_cpu(cpu, HK_FLAG_TICK))
+		return;
+
+	WARN_ON_ONCE(!tick_work_cpu);
+
+	twork = per_cpu_ptr(tick_work_cpu, cpu);
+	cancel_delayed_work_sync(&twork->work);
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
+int __init sched_tick_offload_init(void)
+{
+	tick_work_cpu = alloc_percpu(struct tick_work);
+	BUG_ON(!tick_work_cpu);
+
+	return 0;
+}
+
+#else /* !CONFIG_NO_HZ_FULL */
+static inline void sched_tick_start(int cpu) { }
+static inline void sched_tick_stop(int cpu) { }
 #endif
 
 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
@@ -5786,6 +5836,7 @@ int sched_cpu_starting(unsigned int cpu)
 {
 	set_cpu_rq_start_time(cpu);
 	sched_rq_cpu_starting(cpu);
+	sched_tick_start(cpu);
 	return 0;
 }
 
@@ -5797,6 +5848,7 @@ int sched_cpu_dying(unsigned int cpu)
 
 	/* Handle pending wakeups and then migrate everything off */
 	sched_ttwu_pending();
+	sched_tick_stop(cpu);
 
 	rq_lock_irqsave(rq, &rf);
 	if (rq->rd) {
@@ -5809,7 +5861,7 @@ int sched_cpu_dying(unsigned int cpu)
 
 	calc_load_migrate(rq);
 	update_max_interval();
-	nohz_balance_exit_idle(cpu);
+	nohz_balance_exit_idle(rq);
 	hrtick_clear(rq);
 	return 0;
 }
@@ -6022,13 +6074,11 @@ void __init sched_init(void)
 		rq_attach_root(rq, &def_root_domain);
 #ifdef CONFIG_NO_HZ_COMMON
 		rq->last_load_update_tick = jiffies;
-		rq->nohz_flags = 0;
-#endif
-#ifdef CONFIG_NO_HZ_FULL
-		rq->last_sched_tick = 0;
+		rq->last_blocked_load_update_tick = jiffies;
+		atomic_set(&rq->nohz_flags, 0);
 #endif
 #endif /* CONFIG_SMP */
-		init_rq_hrtick(rq);
+		hrtick_rq_init(rq);
 		atomic_set(&rq->nr_iowait, 0);
 	}
 
@@ -7027,3 +7077,5 @@ const u32 sched_prio_to_wmult[40] = {
  /*  10 */  39045157,  49367440,  61356676,  76695844,  95443717,
  /*  15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
 };
+
+#undef CREATE_TRACE_POINTS

kernel/sched/cpuacct.c

 // SPDX-License-Identifier: GPL-2.0
-#include <linux/cgroup.h>
-#include <linux/slab.h>
-#include <linux/percpu.h>
-#include <linux/spinlock.h>
-#include <linux/cpumask.h>
-#include <linux/seq_file.h>
-#include <linux/rcupdate.h>
-#include <linux/kernel_stat.h>
-#include <linux/err.h>
-
-#include "sched.h"
-
 /*
  * CPU accounting code for task groups.
  *
  * Based on the work by Paul Menage (menage@google.com) and Balbir Singh
  * (balbir@in.ibm.com).
  */
+#include "sched.h"
 
-/* Time spent by the tasks of the cpu accounting group executing in ... */
+/* Time spent by the tasks of the CPU accounting group executing in ... */
 enum cpuacct_stat_index {
 	CPUACCT_STAT_USER,	/* ... user mode */
 	CPUACCT_STAT_SYSTEM,	/* ... kernel mode */
@@ -35,12 +24,12 @@ struct cpuacct_usage {
 	u64	usages[CPUACCT_STAT_NSTATS];
 };
 
-/* track cpu usage of a group of tasks and its child groups */
+/* track CPU usage of a group of tasks and its child groups */
 struct cpuacct {
-	struct cgroup_subsys_state css;
-	/* cpuusage holds pointer to a u64-type object on every cpu */
-	struct cpuacct_usage __percpu *cpuusage;
-	struct kernel_cpustat __percpu *cpustat;
+	struct cgroup_subsys_state	css;
+	/* cpuusage holds pointer to a u64-type object on every CPU */
+	struct cpuacct_usage __percpu	*cpuusage;
+	struct kernel_cpustat __percpu	*cpustat;
 };
 
 static inline struct cpuacct *css_ca(struct cgroup_subsys_state *css)
@@ -48,7 +37,7 @@ static inline struct cpuacct *css_ca(struct cgroup_subsys_state *css)
 	return css ? container_of(css, struct cpuacct, css) : NULL;
 }
 
-/* return cpu accounting group to which this task belongs */
+/* Return CPU accounting group to which this task belongs */
 static inline struct cpuacct *task_ca(struct task_struct *tsk)
 {
 	return css_ca(task_css(tsk, cpuacct_cgrp_id));
@@ -65,7 +54,7 @@ static struct cpuacct root_cpuacct = {
 	.cpuusage	= &root_cpuacct_cpuusage,
 };
 
-/* create a new cpu accounting group */
+/* Create a new CPU accounting group */
 static struct cgroup_subsys_state *
 cpuacct_css_alloc(struct cgroup_subsys_state *parent_css)
 {
@@ -96,7 +85,7 @@ cpuacct_css_alloc(struct cgroup_subsys_state *parent_css)
 	return ERR_PTR(-ENOMEM);
 }
 
-/* destroy an existing cpu accounting group */
+/* Destroy an existing CPU accounting group */
 static void cpuacct_css_free(struct cgroup_subsys_state *css)
 {
 	struct cpuacct *ca = css_ca(css);
@@ -162,7 +151,7 @@ static void cpuacct_cpuusage_write(struct cpuacct *ca, int cpu, u64 val)
 #endif
 }
 
-/* return total cpu usage (in nanoseconds) of a group */
+/* Return total CPU usage (in nanoseconds) of a group */
 static u64 __cpuusage_read(struct cgroup_subsys_state *css,
 			   enum cpuacct_stat_index index)
 {

kernel/sched/cpudeadline.c

@@ -10,11 +10,7 @@
  *  as published by the Free Software Foundation; version 2
  *  of the License.
  */
-
-#include <linux/gfp.h>
-#include <linux/kernel.h>
-#include <linux/slab.h>
-#include "cpudeadline.h"
+#include "sched.h"
 
 static inline int parent(int i)
 {
@@ -42,8 +38,9 @@ static void cpudl_heapify_down(struct cpudl *cp, int idx)
 		return;
 
 	/* adapted from lib/prio_heap.c */
-	while(1) {
+	while (1) {
 		u64 largest_dl;
+
 		l = left_child(idx);
 		r = right_child(idx);
 		largest = idx;
@@ -131,6 +128,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 		return 1;
 	} else {
 		int best_cpu = cpudl_maximum(cp);
+
 		WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
 
 		if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
@@ -145,9 +143,9 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 }
 
 /*
- * cpudl_clear - remove a cpu from the cpudl max-heap
+ * cpudl_clear - remove a CPU from the cpudl max-heap
  * @cp: the cpudl max-heap context
- * @cpu: the target cpu
+ * @cpu: the target CPU
  *
  * Notes: assumes cpu_rq(cpu)->lock is locked
  *
@@ -186,8 +184,8 @@ void cpudl_clear(struct cpudl *cp, int cpu)
 /*
  * cpudl_set - update the cpudl max-heap
  * @cp: the cpudl max-heap context
- * @cpu: the target cpu
- * @dl: the new earliest deadline for this cpu
+ * @cpu: the target CPU
+ * @dl: the new earliest deadline for this CPU
  *
  * Notes: assumes cpu_rq(cpu)->lock is locked
  *
@@ -205,6 +203,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl)
 	old_idx = cp->elements[cpu].idx;
 	if (old_idx == IDX_INVALID) {
 		int new_idx = cp->size++;
+
 		cp->elements[new_idx].dl = dl;
 		cp->elements[new_idx].cpu = cpu;
 		cp->elements[cpu].idx = new_idx;
@@ -221,7 +220,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl)
 /*
  * cpudl_set_freecpu - Set the cpudl.free_cpus
  * @cp: the cpudl max-heap context
- * @cpu: rd attached cpu
+ * @cpu: rd attached CPU
  */
 void cpudl_set_freecpu(struct cpudl *cp, int cpu)
 {
@@ -231,7 +230,7 @@ void cpudl_set_freecpu(struct cpudl *cp, int cpu)
 /*
  * cpudl_clear_freecpu - Clear the cpudl.free_cpus
  * @cp: the cpudl max-heap context
- * @cpu: rd attached cpu
+ * @cpu: rd attached CPU
  */
 void cpudl_clear_freecpu(struct cpudl *cp, int cpu)
 {

kernel/sched/cpudeadline.h

 /* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _LINUX_CPUDL_H
-#define _LINUX_CPUDL_H
 
-#include <linux/sched.h>
-#include <linux/sched/deadline.h>
-
-#define IDX_INVALID     -1
+#define IDX_INVALID		-1
 
 struct cpudl_item {
-	u64 dl;
-	int cpu;
-	int idx;
+	u64			dl;
+	int			cpu;
+	int			idx;
 };
 
 struct cpudl {
-	raw_spinlock_t lock;
-	int size;
-	cpumask_var_t free_cpus;
-	struct cpudl_item *elements;
+	raw_spinlock_t		lock;
+	int			size;
+	cpumask_var_t		free_cpus;
+	struct cpudl_item	*elements;
 };
 
-
 #ifdef CONFIG_SMP
-int cpudl_find(struct cpudl *cp, struct task_struct *p,
-	       struct cpumask *later_mask);
+int  cpudl_find(struct cpudl *cp, struct task_struct *p, struct cpumask *later_mask);
 void cpudl_set(struct cpudl *cp, int cpu, u64 dl);
 void cpudl_clear(struct cpudl *cp, int cpu);
-int cpudl_init(struct cpudl *cp);
+int  cpudl_init(struct cpudl *cp);
 void cpudl_set_freecpu(struct cpudl *cp, int cpu);
 void cpudl_clear_freecpu(struct cpudl *cp, int cpu);
 void cpudl_cleanup(struct cpudl *cp);
 #endif /* CONFIG_SMP */
-
-#endif /* _LINUX_CPUDL_H */

kernel/sched/cpufreq.c

@@ -8,7 +8,6 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
-
 #include "sched.h"
 
 DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);

kernel/sched/cpupri.c

@@ -14,7 +14,7 @@
  *
  *  going from the lowest priority to the highest.  CPUs in the INVALID state
  *  are not eligible for routing.  The system maintains this state with
- *  a 2 dimensional bitmap (the first for priority class, the second for cpus
+ *  a 2 dimensional bitmap (the first for priority class, the second for CPUs
  *  in that class).  Therefore a typical application without affinity
  *  restrictions can find a suitable CPU with O(1) complexity (e.g. two bit
  *  searches).  For tasks with affinity restrictions, the algorithm has a
@@ -26,12 +26,7 @@
  *  as published by the Free Software Foundation; version 2
  *  of the License.
  */
-
-#include <linux/gfp.h>
-#include <linux/sched.h>
-#include <linux/sched/rt.h>
-#include <linux/slab.h>
-#include "cpupri.h"
+#include "sched.h"
 
 /* Convert between a 140 based task->prio, and our 102 based cpupri */
 static int convert_prio(int prio)
@@ -128,9 +123,9 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
 }
 
 /**
- * cpupri_set - update the cpu priority setting
+ * cpupri_set - update the CPU priority setting
  * @cp: The cpupri context
- * @cpu: The target cpu
+ * @cpu: The target CPU
  * @newpri: The priority (INVALID-RT99) to assign to this CPU
  *
  * Note: Assumes cpu_rq(cpu)->lock is locked
@@ -151,7 +146,7 @@ void cpupri_set(struct cpupri *cp, int cpu, int newpri)
 		return;
 
 	/*
-	 * If the cpu was currently mapped to a different value, we
+	 * If the CPU was currently mapped to a different value, we
 	 * need to map it to the new value then remove the old value.
 	 * Note, we must add the new value first, otherwise we risk the
 	 * cpu being missed by the priority loop in cpupri_find.

kernel/sched/cpupri.h

 /* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _LINUX_CPUPRI_H
-#define _LINUX_CPUPRI_H
-
-#include <linux/sched.h>
 
 #define CPUPRI_NR_PRIORITIES	(MAX_RT_PRIO + 2)
 
-#define CPUPRI_INVALID -1
-#define CPUPRI_IDLE     0
-#define CPUPRI_NORMAL   1
+#define CPUPRI_INVALID		-1
+#define CPUPRI_IDLE		 0
+#define CPUPRI_NORMAL		 1
 /* values 2-101 are RT priorities 0-99 */
 
 struct cpupri_vec {
-	atomic_t	count;
-	cpumask_var_t	mask;
+	atomic_t		count;
+	cpumask_var_t		mask;
 };
 
 struct cpupri {
-	struct cpupri_vec pri_to_cpu[CPUPRI_NR_PRIORITIES];
-	int *cpu_to_pri;
+	struct cpupri_vec	pri_to_cpu[CPUPRI_NR_PRIORITIES];
+	int			*cpu_to_pri;
 };
 
 #ifdef CONFIG_SMP
-int  cpupri_find(struct cpupri *cp,
-		 struct task_struct *p, struct cpumask *lowest_mask);
+int  cpupri_find(struct cpupri *cp, struct task_struct *p, struct cpumask *lowest_mask);
 void cpupri_set(struct cpupri *cp, int cpu, int pri);
-int cpupri_init(struct cpupri *cp);
+int  cpupri_init(struct cpupri *cp);
 void cpupri_cleanup(struct cpupri *cp);
 #endif
-
-#endif /* _LINUX_CPUPRI_H */

kernel/sched/cputime.c

-#include <linux/export.h>
-#include <linux/sched.h>
-#include <linux/tsacct_kern.h>
-#include <linux/kernel_stat.h>
-#include <linux/static_key.h>
-#include <linux/context_tracking.h>
-#include <linux/sched/cputime.h>
+/*
+ * Simple CPU accounting cgroup controller
+ */
 #include "sched.h"
 
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
@@ -113,9 +109,9 @@ static inline void task_group_account_field(struct task_struct *p, int index,
 }
 
 /*
- * Account user cpu time to a process.
- * @p: the process that the cpu time gets accounted to
- * @cputime: the cpu time spent in user space since the last update
+ * Account user CPU time to a process.
+ * @p: the process that the CPU time gets accounted to
+ * @cputime: the CPU time spent in user space since the last update
  */
 void account_user_time(struct task_struct *p, u64 cputime)
 {
@@ -135,9 +131,9 @@ void account_user_time(struct task_struct *p, u64 cputime)
 }
 
 /*
- * Account guest cpu time to a process.
- * @p: the process that the cpu time gets accounted to
- * @cputime: the cpu time spent in virtual machine since the last update
+ * Account guest CPU time to a process.
+ * @p: the process that the CPU time gets accounted to
+ * @cputime: the CPU time spent in virtual machine since the last update
  */
 void account_guest_time(struct task_struct *p, u64 cputime)
 {
@@ -159,9 +155,9 @@ void account_guest_time(struct task_struct *p, u64 cputime)
 }
 
 /*
- * Account system cpu time to a process and desired cpustat field
- * @p: the process that the cpu time gets accounted to
- * @cputime: the cpu time spent in kernel space since the last update
+ * Account system CPU time to a process and desired cpustat field
+ * @p: the process that the CPU time gets accounted to
+ * @cputime: the CPU time spent in kernel space since the last update
  * @index: pointer to cpustat field that has to be updated
  */
 void account_system_index_time(struct task_struct *p,
@@ -179,10 +175,10 @@ void account_system_index_time(struct task_struct *p,
 }
 
 /*
- * Account system cpu time to a process.
- * @p: the process that the cpu time gets accounted to
+ * Account system CPU time to a process.
+ * @p: the process that the CPU time gets accounted to
  * @hardirq_offset: the offset to subtract from hardirq_count()
- * @cputime: the cpu time spent in kernel space since the last update
+ * @cputime: the CPU time spent in kernel space since the last update
  */
 void account_system_time(struct task_struct *p, int hardirq_offset, u64 cputime)
 {
@@ -205,7 +201,7 @@ void account_system_time(struct task_struct *p, int hardirq_offset, u64 cputime)
 
 /*
  * Account for involuntary wait time.
- * @cputime: the cpu time spent in involuntary wait
+ * @cputime: the CPU time spent in involuntary wait
  */
 void account_steal_time(u64 cputime)
 {
@@ -216,7 +212,7 @@ void account_steal_time(u64 cputime)
 
 /*
  * Account for idle time.
- * @cputime: the cpu time spent in idle wait
+ * @cputime: the CPU time spent in idle wait
  */
 void account_idle_time(u64 cputime)
 {
@@ -338,7 +334,7 @@ void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 /*
  * Account a tick to a process and cpustat
- * @p: the process that the cpu time gets accounted to
+ * @p: the process that the CPU time gets accounted to
  * @user_tick: is the tick from userspace
  * @rq: the pointer to rq
  *
@@ -400,17 +396,16 @@ static void irqtime_account_idle_ticks(int ticks)
 	irqtime_account_process_tick(current, 0, rq, ticks);
 }
 #else /* CONFIG_IRQ_TIME_ACCOUNTING */
-static inline void irqtime_account_idle_ticks(int ticks) {}
+static inline void irqtime_account_idle_ticks(int ticks) { }
 static inline void irqtime_account_process_tick(struct task_struct *p, int user_tick,
-						struct rq *rq, int nr_ticks) {}
+						struct rq *rq, int nr_ticks) { }
 #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
 
 /*
  * Use precise platform statistics if available:
  */
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
-
-#ifndef __ARCH_HAS_VTIME_TASK_SWITCH
+# ifndef __ARCH_HAS_VTIME_TASK_SWITCH
 void vtime_common_task_switch(struct task_struct *prev)
 {
 	if (is_idle_task(prev))
@@ -421,8 +416,7 @@ void vtime_common_task_switch(struct task_struct *prev)
 	vtime_flush(prev);
 	arch_vtime_task_switch(prev);
 }
-#endif
-
+# endif
 #endif /* CONFIG_VIRT_CPU_ACCOUNTING */
 
 
@@ -469,10 +463,12 @@ void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
 	*ut = cputime.utime;
 	*st = cputime.stime;
 }
-#else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
+
+#else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE: */
+
 /*
- * Account a single tick of cpu time.
- * @p: the process that the cpu time gets accounted to
+ * Account a single tick of CPU time.
+ * @p: the process that the CPU time gets accounted to
  * @user_tick: indicates if the tick is a user or a system tick
  */
 void account_process_tick(struct task_struct *p, int user_tick)

kernel/sched/deadline.c

@@ -17,9 +17,6 @@
  */
 #include "sched.h"
 
-#include <linux/slab.h>
-#include <uapi/linux/sched/types.h>
-
 struct dl_bandwidth def_dl_bandwidth;
 
 static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
@@ -87,7 +84,7 @@ void __add_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
 	SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */
 	SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
 	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
-	cpufreq_update_util(rq_of_dl_rq(dl_rq), SCHED_CPUFREQ_DL);
+	cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
 }
 
 static inline
@@ -101,7 +98,7 @@ void __sub_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
 	if (dl_rq->running_bw > old)
 		dl_rq->running_bw = 0;
 	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
-	cpufreq_update_util(rq_of_dl_rq(dl_rq), SCHED_CPUFREQ_DL);
+	cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
 }
 
 static inline
@@ -514,7 +511,7 @@ static DEFINE_PER_CPU(struct callback_head, dl_pull_head);
 static void push_dl_tasks(struct rq *);
 static void pull_dl_task(struct rq *);
 
-static inline void queue_push_tasks(struct rq *rq)
+static inline void deadline_queue_push_tasks(struct rq *rq)
 {
 	if (!has_pushable_dl_tasks(rq))
 		return;
@@ -522,7 +519,7 @@ static inline void queue_push_tasks(struct rq *rq)
 	queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
 }
 
-static inline void queue_pull_task(struct rq *rq)
+static inline void deadline_queue_pull_task(struct rq *rq)
 {
 	queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
 }
@@ -539,12 +536,12 @@ static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p
 
 		/*
 		 * If we cannot preempt any rq, fall back to pick any
-		 * online cpu.
+		 * online CPU:
 		 */
 		cpu = cpumask_any_and(cpu_active_mask, &p->cpus_allowed);
 		if (cpu >= nr_cpu_ids) {
 			/*
-			 * Fail to find any suitable cpu.
+			 * Failed to find any suitable CPU.
 			 * The task will never come back!
 			 */
 			BUG_ON(dl_bandwidth_enabled());
@@ -597,19 +594,18 @@ static inline void pull_dl_task(struct rq *rq)
 {
 }
 
-static inline void queue_push_tasks(struct rq *rq)
+static inline void deadline_queue_push_tasks(struct rq *rq)
 {
 }
 
-static inline void queue_pull_task(struct rq *rq)
+static inline void deadline_queue_pull_task(struct rq *rq)
 {
 }
 #endif /* CONFIG_SMP */
 
 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
 static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
-static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
-				  int flags);
+static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, int flags);
 
 /*
  * We are being explicitly informed that a new instance is starting,
@@ -1763,7 +1759,7 @@ pick_next_task_dl(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 	if (hrtick_enabled(rq))
 		start_hrtick_dl(rq, p);
 
-	queue_push_tasks(rq);
+	deadline_queue_push_tasks(rq);
 
 	return p;
 }
@@ -1776,6 +1772,14 @@ static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
 		enqueue_pushable_dl_task(rq, p);
 }
 
+/*
+ * scheduler tick hitting a task of our scheduling class.
+ *
+ * NOTE: This function can be called remotely by the tick offload that
+ * goes along full dynticks. Therefore no local assumption can be made
+ * and everything must be accessed through the @rq and @curr passed in
+ * parameters.
+ */
 static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
 {
 	update_curr_dl(rq);
@@ -1865,7 +1869,7 @@ static int find_later_rq(struct task_struct *task)
 
 	/*
 	 * We have to consider system topology and task affinity
-	 * first, then we can look for a suitable cpu.
+	 * first, then we can look for a suitable CPU.
 	 */
 	if (!cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask))
 		return -1;
@@ -1879,7 +1883,7 @@ static int find_later_rq(struct task_struct *task)
 	 * Now we check how well this matches with task's
 	 * affinity and system topology.
 	 *
-	 * The last cpu where the task run is our first
+	 * The last CPU where the task run is our first
 	 * guess, since it is most likely cache-hot there.
 	 */
 	if (cpumask_test_cpu(cpu, later_mask))
@@ -1909,9 +1913,9 @@ static int find_later_rq(struct task_struct *task)
 			best_cpu = cpumask_first_and(later_mask,
 							sched_domain_span(sd));
 			/*
-			 * Last chance: if a cpu being in both later_mask
+			 * Last chance: if a CPU being in both later_mask
 			 * and current sd span is valid, that becomes our
-			 * choice. Of course, the latest possible cpu is
+			 * choice. Of course, the latest possible CPU is
 			 * already under consideration through later_mask.
 			 */
 			if (best_cpu < nr_cpu_ids) {
@@ -2067,7 +2071,7 @@ static int push_dl_task(struct rq *rq)
 		if (task == next_task) {
 			/*
 			 * The task is still there. We don't try
-			 * again, some other cpu will pull it when ready.
+			 * again, some other CPU will pull it when ready.
 			 */
 			goto out;
 		}
@@ -2300,12 +2304,12 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
 	/*
 	 * Since this might be the only -deadline task on the rq,
 	 * this is the right place to try to pull some other one
-	 * from an overloaded cpu, if any.
+	 * from an overloaded CPU, if any.
 	 */
 	if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
 		return;
 
-	queue_pull_task(rq);
+	deadline_queue_pull_task(rq);
 }
 
 /*
@@ -2327,7 +2331,7 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
 	if (rq->curr != p) {
 #ifdef CONFIG_SMP
 		if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
-			queue_push_tasks(rq);
+			deadline_queue_push_tasks(rq);
 #endif
 		if (dl_task(rq->curr))
 			check_preempt_curr_dl(rq, p, 0);
@@ -2352,7 +2356,7 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p,
 		 * or lowering its prio, so...
 		 */
 		if (!rq->dl.overloaded)
-			queue_pull_task(rq);
+			deadline_queue_pull_task(rq);
 
 		/*
 		 * If we now have a earlier deadline task than p,
@@ -2626,17 +2630,17 @@ void __dl_clear_params(struct task_struct *p)
 {
 	struct sched_dl_entity *dl_se = &p->dl;
 
-	dl_se->dl_runtime = 0;
-	dl_se->dl_deadline = 0;
-	dl_se->dl_period = 0;
-	dl_se->flags = 0;
-	dl_se->dl_bw = 0;
-	dl_se->dl_density = 0;
+	dl_se->dl_runtime		= 0;
+	dl_se->dl_deadline		= 0;
+	dl_se->dl_period		= 0;
+	dl_se->flags			= 0;
+	dl_se->dl_bw			= 0;
+	dl_se->dl_density		= 0;
 
-	dl_se->dl_throttled = 0;
-	dl_se->dl_yielded = 0;
-	dl_se->dl_non_contending = 0;
-	dl_se->dl_overrun = 0;
+	dl_se->dl_throttled		= 0;
+	dl_se->dl_yielded		= 0;
+	dl_se->dl_non_contending	= 0;
+	dl_se->dl_overrun		= 0;
 }
 
 bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
@@ -2655,21 +2659,22 @@ bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
 #ifdef CONFIG_SMP
 int dl_task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allowed)
 {
-	unsigned int dest_cpu = cpumask_any_and(cpu_active_mask,
-							cs_cpus_allowed);
+	unsigned int dest_cpu;
 	struct dl_bw *dl_b;
 	bool overflow;
 	int cpus, ret;
 	unsigned long flags;
 
+	dest_cpu = cpumask_any_and(cpu_active_mask, cs_cpus_allowed);
+
 	rcu_read_lock_sched();
 	dl_b = dl_bw_of(dest_cpu);
 	raw_spin_lock_irqsave(&dl_b->lock, flags);
 	cpus = dl_bw_cpus(dest_cpu);
 	overflow = __dl_overflow(dl_b, cpus, 0, p->dl.dl_bw);
-	if (overflow)
+	if (overflow) {
 		ret = -EBUSY;
-	else {
+	} else {
 		/*
 		 * We reserve space for this task in the destination
 		 * root_domain, as we can't fail after this point.
@@ -2681,6 +2686,7 @@ int dl_task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allo
 	}
 	raw_spin_unlock_irqrestore(&dl_b->lock, flags);
 	rcu_read_unlock_sched();
+
 	return ret;
 }
 
@@ -2701,6 +2707,7 @@ int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
 		ret = 0;
 	raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
 	rcu_read_unlock_sched();
+
 	return ret;
 }
 
@@ -2718,6 +2725,7 @@ bool dl_cpu_busy(unsigned int cpu)
 	overflow = __dl_overflow(dl_b, cpus, 0, 0);
 	raw_spin_unlock_irqrestore(&dl_b->lock, flags);
 	rcu_read_unlock_sched();
+
 	return overflow;
 }
 #endif

kernel/sched/debug.c

 /*
  * kernel/sched/debug.c
  *
- * Print the CFS rbtree
+ * Print the CFS rbtree and other debugging details
  *
  * Copyright(C) 2007, Red Hat, Inc., Ingo Molnar
  *
@@ -9,16 +9,6 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
-
-#include <linux/proc_fs.h>
-#include <linux/sched/mm.h>
-#include <linux/sched/task.h>
-#include <linux/seq_file.h>
-#include <linux/kallsyms.h>
-#include <linux/utsname.h>
-#include <linux/mempolicy.h>
-#include <linux/debugfs.h>
-
 #include "sched.h"
 
 static DEFINE_SPINLOCK(sched_debug_lock);
@@ -274,34 +264,19 @@ sd_alloc_ctl_domain_table(struct sched_domain *sd)
 	if (table == NULL)
 		return NULL;
 
-	set_table_entry(&table[0], "min_interval", &sd->min_interval,
-		sizeof(long), 0644, proc_doulongvec_minmax, false);
-	set_table_entry(&table[1], "max_interval", &sd->max_interval,
-		sizeof(long), 0644, proc_doulongvec_minmax, false);
-	set_table_entry(&table[2], "busy_idx", &sd->busy_idx,
-		sizeof(int), 0644, proc_dointvec_minmax, true);
-	set_table_entry(&table[3], "idle_idx", &sd->idle_idx,
-		sizeof(int), 0644, proc_dointvec_minmax, true);
-	set_table_entry(&table[4], "newidle_idx", &sd->newidle_idx,
-		sizeof(int), 0644, proc_dointvec_minmax, true);
-	set_table_entry(&table[5], "wake_idx", &sd->wake_idx,
-		sizeof(int), 0644, proc_dointvec_minmax, true);
-	set_table_entry(&table[6], "forkexec_idx", &sd->forkexec_idx,
-		sizeof(int), 0644, proc_dointvec_minmax, true);
-	set_table_entry(&table[7], "busy_factor", &sd->busy_factor,
-		sizeof(int), 0644, proc_dointvec_minmax, false);
-	set_table_entry(&table[8], "imbalance_pct", &sd->imbalance_pct,
-		sizeof(int), 0644, proc_dointvec_minmax, false);
-	set_table_entry(&table[9], "cache_nice_tries",
-		&sd->cache_nice_tries,
-		sizeof(int), 0644, proc_dointvec_minmax, false);
-	set_table_entry(&table[10], "flags", &sd->flags,
-		sizeof(int), 0644, proc_dointvec_minmax, false);
-	set_table_entry(&table[11], "max_newidle_lb_cost",
-		&sd->max_newidle_lb_cost,
-		sizeof(long), 0644, proc_doulongvec_minmax, false);
-	set_table_entry(&table[12], "name", sd->name,
-		CORENAME_MAX_SIZE, 0444, proc_dostring, false);
+	set_table_entry(&table[0] , "min_interval",	   &sd->min_interval,	     sizeof(long), 0644, proc_doulongvec_minmax, false);
+	set_table_entry(&table[1] , "max_interval",	   &sd->max_interval,	     sizeof(long), 0644, proc_doulongvec_minmax, false);
+	set_table_entry(&table[2] , "busy_idx",		   &sd->busy_idx,	     sizeof(int) , 0644, proc_dointvec_minmax,   true );
+	set_table_entry(&table[3] , "idle_idx",		   &sd->idle_idx,	     sizeof(int) , 0644, proc_dointvec_minmax,   true );
+	set_table_entry(&table[4] , "newidle_idx",	   &sd->newidle_idx,	     sizeof(int) , 0644, proc_dointvec_minmax,   true );
+	set_table_entry(&table[5] , "wake_idx",		   &sd->wake_idx,	     sizeof(int) , 0644, proc_dointvec_minmax,   true );
+	set_table_entry(&table[6] , "forkexec_idx",	   &sd->forkexec_idx,	     sizeof(int) , 0644, proc_dointvec_minmax,   true );
+	set_table_entry(&table[7] , "busy_factor",	   &sd->busy_factor,	     sizeof(int) , 0644, proc_dointvec_minmax,   false);
+	set_table_entry(&table[8] , "imbalance_pct",	   &sd->imbalance_pct,	     sizeof(int) , 0644, proc_dointvec_minmax,   false);
+	set_table_entry(&table[9] , "cache_nice_tries",	   &sd->cache_nice_tries,    sizeof(int) , 0644, proc_dointvec_minmax,   false);
+	set_table_entry(&table[10], "flags",		   &sd->flags,		     sizeof(int) , 0644, proc_dointvec_minmax,   false);
+	set_table_entry(&table[11], "max_newidle_lb_cost", &sd->max_newidle_lb_cost, sizeof(long), 0644, proc_doulongvec_minmax, false);
+	set_table_entry(&table[12], "name",		   sd->name,		CORENAME_MAX_SIZE, 0444, proc_dostring,		 false);
 	/* &table[13] is terminator */
 
 	return table;
@@ -332,8 +307,8 @@ static struct ctl_table *sd_alloc_ctl_cpu_table(int cpu)
 	return table;
 }
 
-static cpumask_var_t sd_sysctl_cpus;
-static struct ctl_table_header *sd_sysctl_header;
+static cpumask_var_t		sd_sysctl_cpus;
+static struct ctl_table_header	*sd_sysctl_header;
 
 void register_sched_domain_sysctl(void)
 {
@@ -413,14 +388,10 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
 {
 	struct sched_entity *se = tg->se[cpu];
 
-#define P(F) \
-	SEQ_printf(m, "  .%-30s: %lld\n", #F, (long long)F)
-#define P_SCHEDSTAT(F) \
-	SEQ_printf(m, "  .%-30s: %lld\n", #F, (long long)schedstat_val(F))
-#define PN(F) \
-	SEQ_printf(m, "  .%-30s: %lld.%06ld\n", #F, SPLIT_NS((long long)F))
-#define PN_SCHEDSTAT(F) \
-	SEQ_printf(m, "  .%-30s: %lld.%06ld\n", #F, SPLIT_NS((long long)schedstat_val(F)))
+#define P(F)		SEQ_printf(m, "  .%-30s: %lld\n",	#F, (long long)F)
+#define P_SCHEDSTAT(F)	SEQ_printf(m, "  .%-30s: %lld\n",	#F, (long long)schedstat_val(F))
+#define PN(F)		SEQ_printf(m, "  .%-30s: %lld.%06ld\n", #F, SPLIT_NS((long long)F))
+#define PN_SCHEDSTAT(F)	SEQ_printf(m, "  .%-30s: %lld.%06ld\n", #F, SPLIT_NS((long long)schedstat_val(F)))
 
 	if (!se)
 		return;
@@ -428,6 +399,7 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
 	PN(se->exec_start);
 	PN(se->vruntime);
 	PN(se->sum_exec_runtime);
+
 	if (schedstat_enabled()) {
 		PN_SCHEDSTAT(se->statistics.wait_start);
 		PN_SCHEDSTAT(se->statistics.sleep_start);
@@ -440,6 +412,7 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
 		PN_SCHEDSTAT(se->statistics.wait_sum);
 		P_SCHEDSTAT(se->statistics.wait_count);
 	}
+
 	P(se->load.weight);
 	P(se->runnable_weight);
 #ifdef CONFIG_SMP
@@ -464,6 +437,7 @@ static char *task_group_path(struct task_group *tg)
 		return group_path;
 
 	cgroup_path(tg->css.cgroup, group_path, PATH_MAX);
+
 	return group_path;
 }
 #endif
@@ -569,6 +543,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
 			cfs_rq->avg.runnable_load_avg);
 	SEQ_printf(m, "  .%-30s: %lu\n", "util_avg",
 			cfs_rq->avg.util_avg);
+	SEQ_printf(m, "  .%-30s: %u\n", "util_est_enqueued",
+			cfs_rq->avg.util_est.enqueued);
 	SEQ_printf(m, "  .%-30s: %ld\n", "removed.load_avg",
 			cfs_rq->removed.load_avg);
 	SEQ_printf(m, "  .%-30s: %ld\n", "removed.util_avg",
@@ -804,9 +780,9 @@ void sysrq_sched_debug_show(void)
 /*
  * This itererator needs some explanation.
  * It returns 1 for the header position.
- * This means 2 is cpu 0.
- * In a hotplugged system some cpus, including cpu 0, may be missing so we have
- * to use cpumask_* to iterate over the cpus.
+ * This means 2 is CPU 0.
+ * In a hotplugged system some CPUs, including CPU 0, may be missing so we have
+ * to use cpumask_* to iterate over the CPUs.
  */
 static void *sched_debug_start(struct seq_file *file, loff_t *offset)
 {
@@ -826,6 +802,7 @@ static void *sched_debug_start(struct seq_file *file, loff_t *offset)
 
 	if (n < nr_cpu_ids)
 		return (void *)(unsigned long)(n + 2);
+
 	return NULL;
 }
 
@@ -840,10 +817,10 @@ static void sched_debug_stop(struct seq_file *file, void *data)
 }
 
 static const struct seq_operations sched_debug_sops = {
-	.start = sched_debug_start,
-	.next = sched_debug_next,
-	.stop = sched_debug_stop,
-	.show = sched_debug_show,
+	.start		= sched_debug_start,
+	.next		= sched_debug_next,
+	.stop		= sched_debug_stop,
+	.show		= sched_debug_show,
 };
 
 static int sched_debug_release(struct inode *inode, struct file *file)
@@ -881,14 +858,10 @@ static int __init init_sched_debug_procfs(void)
 
 __initcall(init_sched_debug_procfs);
 
-#define __P(F) \
-	SEQ_printf(m, "%-45s:%21Ld\n", #F, (long long)F)
-#define P(F) \
-	SEQ_printf(m, "%-45s:%21Ld\n", #F, (long long)p->F)
-#define __PN(F) \
-	SEQ_printf(m, "%-45s:%14Ld.%06ld\n", #F, SPLIT_NS((long long)F))
-#define PN(F) \
-	SEQ_printf(m, "%-45s:%14Ld.%06ld\n", #F, SPLIT_NS((long long)p->F))
+#define __P(F)	SEQ_printf(m, "%-45s:%21Ld\n",	     #F, (long long)F)
+#define   P(F)	SEQ_printf(m, "%-45s:%21Ld\n",	     #F, (long long)p->F)
+#define __PN(F)	SEQ_printf(m, "%-45s:%14Ld.%06ld\n", #F, SPLIT_NS((long long)F))
+#define   PN(F)	SEQ_printf(m, "%-45s:%14Ld.%06ld\n", #F, SPLIT_NS((long long)p->F))
 
 
 #ifdef CONFIG_NUMA_BALANCING
@@ -1023,6 +996,8 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
 	P(se.avg.runnable_load_avg);
 	P(se.avg.util_avg);
 	P(se.avg.last_update_time);
+	P(se.avg.util_est.ewma);
+	P(se.avg.util_est.enqueued);
 #endif
 	P(policy);
 	P(prio);

kernel/sched/features.h

@@ -85,3 +85,8 @@ SCHED_FEAT(ATTACH_AGE_LOAD, true)
 SCHED_FEAT(WA_IDLE, true)
 SCHED_FEAT(WA_WEIGHT, true)
 SCHED_FEAT(WA_BIAS, true)
+
+/*
+ * UtilEstimation. Use estimated CPU utilization.
+ */
+SCHED_FEAT(UTIL_EST, true)

kernel/sched/idle.c

 /*
- * Generic entry point for the idle threads
+ * Generic entry points for the idle threads and
+ * implementation of the idle task scheduling class.
+ *
+ * (NOTE: these are not related to SCHED_IDLE batch scheduled
+ *        tasks which are handled in sched/fair.c )
  */
-#include <linux/sched.h>
-#include <linux/sched/idle.h>
-#include <linux/cpu.h>
-#include <linux/cpuidle.h>
-#include <linux/cpuhotplug.h>
-#include <linux/tick.h>
-#include <linux/mm.h>
-#include <linux/stackprotector.h>
-#include <linux/suspend.h>
-#include <linux/livepatch.h>
-
-#include <asm/tlb.h>
+#include "sched.h"
 
 #include <trace/events/power.h>
 
-#include "sched.h"
-
 /* Linker adds these: start and end of __cpuidle functions */
 extern char __cpuidle_text_start[], __cpuidle_text_end[];
 
@@ -46,6 +37,7 @@ void cpu_idle_poll_ctrl(bool enable)
 static int __init cpu_idle_poll_setup(char *__unused)
 {
 	cpu_idle_force_poll = 1;
+
 	return 1;
 }
 __setup("nohlt", cpu_idle_poll_setup);
@@ -53,6 +45,7 @@ __setup("nohlt", cpu_idle_poll_setup);
 static int __init cpu_idle_nopoll_setup(char *__unused)
 {
 	cpu_idle_force_poll = 0;
+
 	return 1;
 }
 __setup("hlt", cpu_idle_nopoll_setup);
@@ -64,12 +57,14 @@ static noinline int __cpuidle cpu_idle_poll(void)
 	trace_cpu_idle_rcuidle(0, smp_processor_id());
 	local_irq_enable();
 	stop_critical_timings();
+
 	while (!tif_need_resched() &&
 		(cpu_idle_force_poll || tick_check_broadcast_expired()))
 		cpu_relax();
 	start_critical_timings();
 	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
 	rcu_idle_exit();
+
 	return 1;
 }
 
@@ -332,8 +327,8 @@ void cpu_startup_entry(enum cpuhp_state state)
 {
 	/*
 	 * This #ifdef needs to die, but it's too late in the cycle to
-	 * make this generic (arm and sh have never invoked the canary
-	 * init for the non boot cpus!). Will be fixed in 3.11
+	 * make this generic (ARM and SH have never invoked the canary
+	 * init for the non boot CPUs!). Will be fixed in 3.11
 	 */
 #ifdef CONFIG_X86
 	/*
@@ -350,3 +345,116 @@ void cpu_startup_entry(enum cpuhp_state state)
 	while (1)
 		do_idle();
 }
+
+/*
+ * idle-task scheduling class.
+ */
+
+#ifdef CONFIG_SMP
+static int
+select_task_rq_idle(struct task_struct *p, int cpu, int sd_flag, int flags)
+{
+	return task_cpu(p); /* IDLE tasks as never migrated */
+}
+#endif
+
+/*
+ * Idle tasks are unconditionally rescheduled:
+ */
+static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
+{
+	resched_curr(rq);
+}
+
+static struct task_struct *
+pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+{
+	put_prev_task(rq, prev);
+	update_idle_core(rq);
+	schedstat_inc(rq->sched_goidle);
+
+	return rq->idle;
+}
+
+/*
+ * It is not legal to sleep in the idle task - print a warning
+ * message if some code attempts to do it:
+ */
+static void
+dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
+{
+	raw_spin_unlock_irq(&rq->lock);
+	printk(KERN_ERR "bad: scheduling from the idle thread!\n");
+	dump_stack();
+	raw_spin_lock_irq(&rq->lock);
+}
+
+static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
+{
+}
+
+/*
+ * scheduler tick hitting a task of our scheduling class.
+ *
+ * NOTE: This function can be called remotely by the tick offload that
+ * goes along full dynticks. Therefore no local assumption can be made
+ * and everything must be accessed through the @rq and @curr passed in
+ * parameters.
+ */
+static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
+{
+}
+
+static void set_curr_task_idle(struct rq *rq)
+{
+}
+
+static void switched_to_idle(struct rq *rq, struct task_struct *p)
+{
+	BUG();
+}
+
+static void
+prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
+{
+	BUG();
+}
+
+static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
+{
+	return 0;
+}
+
+static void update_curr_idle(struct rq *rq)
+{
+}
+
+/*
+ * Simple, special scheduling class for the per-CPU idle tasks:
+ */
+const struct sched_class idle_sched_class = {
+	/* .next is NULL */
+	/* no enqueue/yield_task for idle tasks */
+
+	/* dequeue is not valid, we print a debug message there: */
+	.dequeue_task		= dequeue_task_idle,
+
+	.check_preempt_curr	= check_preempt_curr_idle,
+
+	.pick_next_task		= pick_next_task_idle,
+	.put_prev_task		= put_prev_task_idle,
+
+#ifdef CONFIG_SMP
+	.select_task_rq		= select_task_rq_idle,
+	.set_cpus_allowed	= set_cpus_allowed_common,
+#endif
+
+	.set_curr_task          = set_curr_task_idle,
+	.task_tick		= task_tick_idle,
+
+	.get_rr_interval	= get_rr_interval_idle,
+
+	.prio_changed		= prio_changed_idle,
+	.switched_to		= switched_to_idle,
+	.update_curr		= update_curr_idle,
+};

kernel/sched/idle_task.c

-// SPDX-License-Identifier: GPL-2.0
-#include "sched.h"
-
-/*
- * idle-task scheduling class.
- *
- * (NOTE: these are not related to SCHED_IDLE tasks which are
- *  handled in sched/fair.c)
- */
-
-#ifdef CONFIG_SMP
-static int
-select_task_rq_idle(struct task_struct *p, int cpu, int sd_flag, int flags)
-{
-	return task_cpu(p); /* IDLE tasks as never migrated */
-}
-#endif /* CONFIG_SMP */
-
-/*
- * Idle tasks are unconditionally rescheduled:
- */
-static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
-{
-	resched_curr(rq);
-}
-
-static struct task_struct *
-pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
-{
-	put_prev_task(rq, prev);
-	update_idle_core(rq);
-	schedstat_inc(rq->sched_goidle);
-	return rq->idle;
-}
-
-/*
- * It is not legal to sleep in the idle task - print a warning
- * message if some code attempts to do it:
- */
-static void
-dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
-{
-	raw_spin_unlock_irq(&rq->lock);
-	printk(KERN_ERR "bad: scheduling from the idle thread!\n");
-	dump_stack();
-	raw_spin_lock_irq(&rq->lock);
-}
-
-static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
-{
-	rq_last_tick_reset(rq);
-}
-
-static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
-{
-}
-
-static void set_curr_task_idle(struct rq *rq)
-{
-}
-
-static void switched_to_idle(struct rq *rq, struct task_struct *p)
-{
-	BUG();
-}
-
-static void
-prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
-{
-	BUG();
-}
-
-static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
-{
-	return 0;
-}
-
-static void update_curr_idle(struct rq *rq)
-{
-}
-
-/*
- * Simple, special scheduling class for the per-CPU idle tasks:
- */
-const struct sched_class idle_sched_class = {
-	/* .next is NULL */
-	/* no enqueue/yield_task for idle tasks */
-
-	/* dequeue is not valid, we print a debug message there: */
-	.dequeue_task		= dequeue_task_idle,
-
-	.check_preempt_curr	= check_preempt_curr_idle,
-
-	.pick_next_task		= pick_next_task_idle,
-	.put_prev_task		= put_prev_task_idle,
-
-#ifdef CONFIG_SMP
-	.select_task_rq		= select_task_rq_idle,
-	.set_cpus_allowed	= set_cpus_allowed_common,
-#endif
-
-	.set_curr_task          = set_curr_task_idle,
-	.task_tick		= task_tick_idle,
-
-	.get_rr_interval	= get_rr_interval_idle,
-
-	.prio_changed		= prio_changed_idle,
-	.switched_to		= switched_to_idle,
-	.update_curr		= update_curr_idle,
-};

kernel/sched/isolation.c

@@ -3,15 +3,10 @@
  *  any CPU: unbound workqueues, timers, kthreads and any offloadable work.
  *
  * Copyright (C) 2017 Red Hat, Inc., Frederic Weisbecker
+ * Copyright (C) 2017-2018 SUSE, Frederic Weisbecker
  *
  */
-
-#include <linux/sched/isolation.h>
-#include <linux/tick.h>
-#include <linux/init.h>
-#include <linux/kernel.h>
-#include <linux/static_key.h>
-#include <linux/ctype.h>
+#include "sched.h"
 
 DEFINE_STATIC_KEY_FALSE(housekeeping_overriden);
 EXPORT_SYMBOL_GPL(housekeeping_overriden);
@@ -60,6 +55,9 @@ void __init housekeeping_init(void)
 
 	static_branch_enable(&housekeeping_overriden);
 
+	if (housekeeping_flags & HK_FLAG_TICK)
+		sched_tick_offload_init();
+
 	/* We need at least one CPU to handle housekeeping work */
 	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
 }
@@ -119,7 +117,7 @@ static int __init housekeeping_nohz_full_setup(char *str)
 {
 	unsigned int flags;
 
-	flags = HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
+	flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
 
 	return housekeeping_setup(str, flags);
 }

kernel/sched/loadavg.c

@@ -6,10 +6,6 @@
  * figure. Its a silly number but people think its important. We go through
  * great pains to make it work on big machines and tickless kernels.
  */
-
-#include <linux/export.h>
-#include <linux/sched/loadavg.h>
-
 #include "sched.h"
 
 /*
@@ -32,29 +28,29 @@
  * Due to a number of reasons the above turns in the mess below:
  *
  *  - for_each_possible_cpu() is prohibitively expensive on machines with
- *    serious number of cpus, therefore we need to take a distributed approach
+ *    serious number of CPUs, therefore we need to take a distributed approach
  *    to calculating nr_active.
  *
  *        \Sum_i x_i(t) = \Sum_i x_i(t) - x_i(t_0) | x_i(t_0) := 0
  *                      = \Sum_i { \Sum_j=1 x_i(t_j) - x_i(t_j-1) }
  *
  *    So assuming nr_active := 0 when we start out -- true per definition, we
- *    can simply take per-cpu deltas and fold those into a global accumulate
+ *    can simply take per-CPU deltas and fold those into a global accumulate
  *    to obtain the same result. See calc_load_fold_active().
  *
- *    Furthermore, in order to avoid synchronizing all per-cpu delta folding
+ *    Furthermore, in order to avoid synchronizing all per-CPU delta folding
  *    across the machine, we assume 10 ticks is sufficient time for every
- *    cpu to have completed this task.
+ *    CPU to have completed this task.
  *
  *    This places an upper-bound on the IRQ-off latency of the machine. Then
  *    again, being late doesn't loose the delta, just wrecks the sample.
  *
- *  - cpu_rq()->nr_uninterruptible isn't accurately tracked per-cpu because
- *    this would add another cross-cpu cacheline miss and atomic operation
- *    to the wakeup path. Instead we increment on whatever cpu the task ran
- *    when it went into uninterruptible state and decrement on whatever cpu
+ *  - cpu_rq()->nr_uninterruptible isn't accurately tracked per-CPU because
+ *    this would add another cross-CPU cacheline miss and atomic operation
+ *    to the wakeup path. Instead we increment on whatever CPU the task ran
+ *    when it went into uninterruptible state and decrement on whatever CPU
  *    did the wakeup. This means that only the sum of nr_uninterruptible over
- *    all cpus yields the correct result.
+ *    all CPUs yields the correct result.
  *
  *  This covers the NO_HZ=n code, for extra head-aches, see the comment below.
  */
@@ -115,11 +111,11 @@ calc_load(unsigned long load, unsigned long exp, unsigned long active)
  * Handle NO_HZ for the global load-average.
  *
  * Since the above described distributed algorithm to compute the global
- * load-average relies on per-cpu sampling from the tick, it is affected by
+ * load-average relies on per-CPU sampling from the tick, it is affected by
  * NO_HZ.
  *
  * The basic idea is to fold the nr_active delta into a global NO_HZ-delta upon
- * entering NO_HZ state such that we can include this as an 'extra' cpu delta
+ * entering NO_HZ state such that we can include this as an 'extra' CPU delta
  * when we read the global state.
  *
  * Obviously reality has to ruin such a delightfully simple scheme:
@@ -146,9 +142,9 @@ calc_load(unsigned long load, unsigned long exp, unsigned long active)
  *    busy state.
  *
  *    This is solved by pushing the window forward, and thus skipping the
- *    sample, for this cpu (effectively using the NO_HZ-delta for this cpu which
+ *    sample, for this CPU (effectively using the NO_HZ-delta for this CPU which
  *    was in effect at the time the window opened). This also solves the issue
- *    of having to deal with a cpu having been in NO_HZ for multiple LOAD_FREQ
+ *    of having to deal with a CPU having been in NO_HZ for multiple LOAD_FREQ
  *    intervals.
  *
  * When making the ILB scale, we should try to pull this in as well.
@@ -299,7 +295,7 @@ calc_load_n(unsigned long load, unsigned long exp,
 }
 
 /*
- * NO_HZ can leave us missing all per-cpu ticks calling
+ * NO_HZ can leave us missing all per-CPU ticks calling
  * calc_load_fold_active(), but since a NO_HZ CPU folds its delta into
  * calc_load_nohz per calc_load_nohz_start(), all we need to do is fold
  * in the pending NO_HZ delta if our NO_HZ period crossed a load cycle boundary.
@@ -363,7 +359,7 @@ void calc_global_load(unsigned long ticks)
 		return;
 
 	/*
-	 * Fold the 'old' NO_HZ-delta to include all NO_HZ cpus.
+	 * Fold the 'old' NO_HZ-delta to include all NO_HZ CPUs.
 	 */
 	delta = calc_load_nohz_fold();
 	if (delta)

kernel/sched/membarrier.c

@@ -13,32 +13,25 @@
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  */
-
-#include <linux/syscalls.h>
-#include <linux/membarrier.h>
-#include <linux/tick.h>
-#include <linux/cpumask.h>
-#include <linux/atomic.h>
-
-#include "sched.h"	/* for cpu_rq(). */
+#include "sched.h"
 
 /*
  * Bitmask made from a "or" of all commands within enum membarrier_cmd,
  * except MEMBARRIER_CMD_QUERY.
  */
 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE
-#define MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK	\
-	(MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE \
+#define MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK			\
+	(MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE			\
 	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE)
 #else
 #define MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK	0
 #endif
 
-#define MEMBARRIER_CMD_BITMASK	\
-	(MEMBARRIER_CMD_GLOBAL | MEMBARRIER_CMD_GLOBAL_EXPEDITED \
-	| MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED \
-	| MEMBARRIER_CMD_PRIVATE_EXPEDITED	\
-	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED	\
+#define MEMBARRIER_CMD_BITMASK						\
+	(MEMBARRIER_CMD_GLOBAL | MEMBARRIER_CMD_GLOBAL_EXPEDITED	\
+	| MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED			\
+	| MEMBARRIER_CMD_PRIVATE_EXPEDITED				\
+	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED			\
 	| MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK)
 
 static void ipi_mb(void *info)
@@ -85,6 +78,7 @@ static int membarrier_global_expedited(void)
 		 */
 		if (cpu == raw_smp_processor_id())
 			continue;
+
 		rcu_read_lock();
 		p = task_rcu_dereference(&cpu_rq(cpu)->curr);
 		if (p && p->mm && (atomic_read(&p->mm->membarrier_state) &
@@ -188,6 +182,7 @@ static int membarrier_private_expedited(int flags)
 	 * rq->curr modification in scheduler.
 	 */
 	smp_mb();	/* exit from system call is not a mb */
+
 	return 0;
 }
 
@@ -219,6 +214,7 @@ static int membarrier_register_global_expedited(void)
 	}
 	atomic_or(MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY,
 		  &mm->membarrier_state);
+
 	return 0;
 }
 
@@ -253,6 +249,7 @@ static int membarrier_register_private_expedited(int flags)
 		synchronize_sched();
 	}
 	atomic_or(state, &mm->membarrier_state);
+
 	return 0;
 }
 

kernel/sched/rt.c

@@ -3,12 +3,8 @@
  * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
  * policies)
  */
-
 #include "sched.h"
 
-#include <linux/slab.h>
-#include <linux/irq_work.h>
-
 int sched_rr_timeslice = RR_TIMESLICE;
 int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
 
@@ -359,7 +355,7 @@ static DEFINE_PER_CPU(struct callback_head, rt_pull_head);
 static void push_rt_tasks(struct rq *);
 static void pull_rt_task(struct rq *);
 
-static inline void queue_push_tasks(struct rq *rq)
+static inline void rt_queue_push_tasks(struct rq *rq)
 {
 	if (!has_pushable_tasks(rq))
 		return;
@@ -367,7 +363,7 @@ static inline void queue_push_tasks(struct rq *rq)
 	queue_balance_callback(rq, &per_cpu(rt_push_head, rq->cpu), push_rt_tasks);
 }
 
-static inline void queue_pull_task(struct rq *rq)
+static inline void rt_queue_pull_task(struct rq *rq)
 {
 	queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);
 }
@@ -425,7 +421,7 @@ static inline void pull_rt_task(struct rq *this_rq)
 {
 }
 
-static inline void queue_push_tasks(struct rq *rq)
+static inline void rt_queue_push_tasks(struct rq *rq)
 {
 }
 #endif /* CONFIG_SMP */
@@ -961,9 +957,6 @@ static void update_curr_rt(struct rq *rq)
 	if (unlikely((s64)delta_exec <= 0))
 		return;
 
-	/* Kick cpufreq (see the comment in kernel/sched/sched.h). */
-	cpufreq_update_util(rq, SCHED_CPUFREQ_RT);
-
 	schedstat_set(curr->se.statistics.exec_max,
 		      max(curr->se.statistics.exec_max, delta_exec));
 
@@ -1005,6 +998,9 @@ dequeue_top_rt_rq(struct rt_rq *rt_rq)
 
 	sub_nr_running(rq, rt_rq->rt_nr_running);
 	rt_rq->rt_queued = 0;
+
+	/* Kick cpufreq (see the comment in kernel/sched/sched.h). */
+	cpufreq_update_util(rq, 0);
 }
 
 static void
@@ -1021,6 +1017,9 @@ enqueue_top_rt_rq(struct rt_rq *rt_rq)
 
 	add_nr_running(rq, rt_rq->rt_nr_running);
 	rt_rq->rt_queued = 1;
+
+	/* Kick cpufreq (see the comment in kernel/sched/sched.h). */
+	cpufreq_update_util(rq, 0);
 }
 
 #if defined CONFIG_SMP
@@ -1453,9 +1452,9 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
 		return;
 
 	/*
-	 * There appears to be other cpus that can accept
-	 * current and none to run 'p', so lets reschedule
-	 * to try and push current away:
+	 * There appear to be other CPUs that can accept
+	 * the current task but none can run 'p', so lets reschedule
+	 * to try and push the current task away:
 	 */
 	requeue_task_rt(rq, p, 1);
 	resched_curr(rq);
@@ -1569,7 +1568,7 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 	/* The running task is never eligible for pushing */
 	dequeue_pushable_task(rq, p);
 
-	queue_push_tasks(rq);
+	rt_queue_push_tasks(rq);
 
 	return p;
 }
@@ -1596,12 +1595,13 @@ static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
 	if (!task_running(rq, p) &&
 	    cpumask_test_cpu(cpu, &p->cpus_allowed))
 		return 1;
+
 	return 0;
 }
 
 /*
  * Return the highest pushable rq's task, which is suitable to be executed
- * on the cpu, NULL otherwise
+ * on the CPU, NULL otherwise
  */
 static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
 {
@@ -1639,11 +1639,11 @@ static int find_lowest_rq(struct task_struct *task)
 		return -1; /* No targets found */
 
 	/*
-	 * At this point we have built a mask of cpus representing the
+	 * At this point we have built a mask of CPUs representing the
 	 * lowest priority tasks in the system.  Now we want to elect
 	 * the best one based on our affinity and topology.
 	 *
-	 * We prioritize the last cpu that the task executed on since
+	 * We prioritize the last CPU that the task executed on since
 	 * it is most likely cache-hot in that location.
 	 */
 	if (cpumask_test_cpu(cpu, lowest_mask))
@@ -1651,7 +1651,7 @@ static int find_lowest_rq(struct task_struct *task)
 
 	/*
 	 * Otherwise, we consult the sched_domains span maps to figure
-	 * out which cpu is logically closest to our hot cache data.
+	 * out which CPU is logically closest to our hot cache data.
 	 */
 	if (!cpumask_test_cpu(this_cpu, lowest_mask))
 		this_cpu = -1; /* Skip this_cpu opt if not among lowest */
@@ -1692,6 +1692,7 @@ static int find_lowest_rq(struct task_struct *task)
 	cpu = cpumask_any(lowest_mask);
 	if (cpu < nr_cpu_ids)
 		return cpu;
+
 	return -1;
 }
 
@@ -1827,7 +1828,7 @@ static int push_rt_task(struct rq *rq)
 			 * The task hasn't migrated, and is still the next
 			 * eligible task, but we failed to find a run-queue
 			 * to push it to.  Do not retry in this case, since
-			 * other cpus will pull from us when ready.
+			 * other CPUs will pull from us when ready.
 			 */
 			goto out;
 		}
@@ -1919,7 +1920,7 @@ static int rto_next_cpu(struct root_domain *rd)
 	 * rt_next_cpu() will simply return the first CPU found in
 	 * the rto_mask.
 	 *
-	 * If rto_next_cpu() is called with rto_cpu is a valid cpu, it
+	 * If rto_next_cpu() is called with rto_cpu is a valid CPU, it
 	 * will return the next CPU found in the rto_mask.
 	 *
 	 * If there are no more CPUs left in the rto_mask, then a check is made
@@ -1980,7 +1981,7 @@ static void tell_cpu_to_push(struct rq *rq)
 	raw_spin_lock(&rq->rd->rto_lock);
 
 	/*
-	 * The rto_cpu is updated under the lock, if it has a valid cpu
+	 * The rto_cpu is updated under the lock, if it has a valid CPU
 	 * then the IPI is still running and will continue due to the
 	 * update to loop_next, and nothing needs to be done here.
 	 * Otherwise it is finishing up and an ipi needs to be sent.
@@ -2105,7 +2106,7 @@ static void pull_rt_task(struct rq *this_rq)
 
 			/*
 			 * There's a chance that p is higher in priority
-			 * than what's currently running on its cpu.
+			 * than what's currently running on its CPU.
 			 * This is just that p is wakeing up and hasn't
 			 * had a chance to schedule. We only pull
 			 * p if it is lower in priority than the
@@ -2187,7 +2188,7 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
 	if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
 		return;
 
-	queue_pull_task(rq);
+	rt_queue_pull_task(rq);
 }
 
 void __init init_sched_rt_class(void)
@@ -2218,7 +2219,7 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p)
 	if (task_on_rq_queued(p) && rq->curr != p) {
 #ifdef CONFIG_SMP
 		if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
-			queue_push_tasks(rq);
+			rt_queue_push_tasks(rq);
 #endif /* CONFIG_SMP */
 		if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq)))
 			resched_curr(rq);
@@ -2242,7 +2243,7 @@ prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
 		 * may need to pull tasks to this runqueue.
 		 */
 		if (oldprio < p->prio)
-			queue_pull_task(rq);
+			rt_queue_pull_task(rq);
 
 		/*
 		 * If there's a higher priority task waiting to run
@@ -2292,6 +2293,14 @@ static void watchdog(struct rq *rq, struct task_struct *p)
 static inline void watchdog(struct rq *rq, struct task_struct *p) { }
 #endif
 
+/*
+ * scheduler tick hitting a task of our scheduling class.
+ *
+ * NOTE: This function can be called remotely by the tick offload that
+ * goes along full dynticks. Therefore no local assumption can be made
+ * and everything must be accessed through the @rq and @curr passed in
+ * parameters.
+ */
 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
 {
 	struct sched_rt_entity *rt_se = &p->rt;
@@ -2685,6 +2694,7 @@ int sched_rr_handler(struct ctl_table *table, int write,
 			msecs_to_jiffies(sysctl_sched_rr_timeslice);
 	}
 	mutex_unlock(&mutex);
+
 	return ret;
 }
 

kernel/sched/stats.c

 // SPDX-License-Identifier: GPL-2.0
-
-#include <linux/slab.h>
-#include <linux/fs.h>
-#include <linux/seq_file.h>
-#include <linux/proc_fs.h>
-
+/*
+ * /proc/schedstat implementation
+ */
 #include "sched.h"
 
 /*
- * bump this up when changing the output format or the meaning of an existing
+ * Current schedstat API version.
+ *
+ * Bump this up when changing the output format or the meaning of an existing
  * format, so that tools can adapt (or abort)
  */
 #define SCHEDSTAT_VERSION 15
@@ -78,8 +77,8 @@ static int show_schedstat(struct seq_file *seq, void *v)
  * This itererator needs some explanation.
  * It returns 1 for the header position.
  * This means 2 is cpu 0.
- * In a hotplugged system some cpus, including cpu 0, may be missing so we have
- * to use cpumask_* to iterate over the cpus.
+ * In a hotplugged system some CPUs, including cpu 0, may be missing so we have
+ * to use cpumask_* to iterate over the CPUs.
  */
 static void *schedstat_start(struct seq_file *file, loff_t *offset)
 {
@@ -99,12 +98,14 @@ static void *schedstat_start(struct seq_file *file, loff_t *offset)
 
 	if (n < nr_cpu_ids)
 		return (void *)(unsigned long)(n + 2);
+
 	return NULL;
 }
 
 static void *schedstat_next(struct seq_file *file, void *data, loff_t *offset)
 {
 	(*offset)++;
+
 	return schedstat_start(file, offset);
 }
 
@@ -134,6 +135,7 @@ static const struct file_operations proc_schedstat_operations = {
 static int __init proc_schedstat_init(void)
 {
 	proc_create("schedstat", 0, NULL, &proc_schedstat_operations);
+
 	return 0;
 }
 subsys_initcall(proc_schedstat_init);

kernel/sched/stats.h

@@ -30,35 +30,29 @@ rq_sched_info_dequeued(struct rq *rq, unsigned long long delta)
 	if (rq)
 		rq->rq_sched_info.run_delay += delta;
 }
-#define schedstat_enabled()		static_branch_unlikely(&sched_schedstats)
+#define   schedstat_enabled()		static_branch_unlikely(&sched_schedstats)
 #define __schedstat_inc(var)		do { var++; } while (0)
-#define schedstat_inc(var)		do { if (schedstat_enabled()) { var++; } } while (0)
+#define   schedstat_inc(var)		do { if (schedstat_enabled()) { var++; } } while (0)
 #define __schedstat_add(var, amt)	do { var += (amt); } while (0)
-#define schedstat_add(var, amt)		do { if (schedstat_enabled()) { var += (amt); } } while (0)
-#define __schedstat_set(var, val)		do { var = (val); } while (0)
-#define schedstat_set(var, val)		do { if (schedstat_enabled()) { var = (val); } } while (0)
-#define schedstat_val(var)		(var)
-#define schedstat_val_or_zero(var)	((schedstat_enabled()) ? (var) : 0)
-
-#else /* !CONFIG_SCHEDSTATS */
-static inline void
-rq_sched_info_arrive(struct rq *rq, unsigned long long delta)
-{}
-static inline void
-rq_sched_info_dequeued(struct rq *rq, unsigned long long delta)
-{}
-static inline void
-rq_sched_info_depart(struct rq *rq, unsigned long long delta)
-{}
-#define schedstat_enabled()		0
-#define __schedstat_inc(var)		do { } while (0)
-#define schedstat_inc(var)		do { } while (0)
-#define __schedstat_add(var, amt)	do { } while (0)
-#define schedstat_add(var, amt)		do { } while (0)
-#define __schedstat_set(var, val)	do { } while (0)
-#define schedstat_set(var, val)		do { } while (0)
-#define schedstat_val(var)		0
-#define schedstat_val_or_zero(var)	0
+#define   schedstat_add(var, amt)	do { if (schedstat_enabled()) { var += (amt); } } while (0)
+#define __schedstat_set(var, val)	do { var = (val); } while (0)
+#define   schedstat_set(var, val)	do { if (schedstat_enabled()) { var = (val); } } while (0)
+#define   schedstat_val(var)		(var)
+#define   schedstat_val_or_zero(var)	((schedstat_enabled()) ? (var) : 0)
+
+#else /* !CONFIG_SCHEDSTATS: */
+static inline void rq_sched_info_arrive  (struct rq *rq, unsigned long long delta) { }
+static inline void rq_sched_info_dequeued(struct rq *rq, unsigned long long delta) { }
+static inline void rq_sched_info_depart  (struct rq *rq, unsigned long long delta) { }
+# define   schedstat_enabled()		0
+# define __schedstat_inc(var)		do { } while (0)
+# define   schedstat_inc(var)		do { } while (0)
+# define __schedstat_add(var, amt)	do { } while (0)
+# define   schedstat_add(var, amt)	do { } while (0)
+# define __schedstat_set(var, val)	do { } while (0)
+# define   schedstat_set(var, val)	do { } while (0)
+# define   schedstat_val(var)		0
+# define   schedstat_val_or_zero(var)	0
 #endif /* CONFIG_SCHEDSTATS */
 
 #ifdef CONFIG_SCHED_INFO
@@ -69,9 +63,9 @@ static inline void sched_info_reset_dequeued(struct task_struct *t)
 
 /*
  * We are interested in knowing how long it was from the *first* time a
- * task was queued to the time that it finally hit a cpu, we call this routine
- * from dequeue_task() to account for possible rq->clock skew across cpus. The
- * delta taken on each cpu would annul the skew.
+ * task was queued to the time that it finally hit a CPU, we call this routine
+ * from dequeue_task() to account for possible rq->clock skew across CPUs. The
+ * delta taken on each CPU would annul the skew.
  */
 static inline void sched_info_dequeued(struct rq *rq, struct task_struct *t)
 {
@@ -87,7 +81,7 @@ static inline void sched_info_dequeued(struct rq *rq, struct task_struct *t)
 }
 
 /*
- * Called when a task finally hits the cpu.  We can now calculate how
+ * Called when a task finally hits the CPU.  We can now calculate how
  * long it was waiting to run.  We also note when it began so that we
  * can keep stats on how long its timeslice is.
  */
@@ -112,9 +106,10 @@ static void sched_info_arrive(struct rq *rq, struct task_struct *t)
  */
 static inline void sched_info_queued(struct rq *rq, struct task_struct *t)
 {
-	if (unlikely(sched_info_on()))
+	if (unlikely(sched_info_on())) {
 		if (!t->sched_info.last_queued)
 			t->sched_info.last_queued = rq_clock(rq);
+	}
 }
 
 /*
@@ -127,8 +122,7 @@ static inline void sched_info_queued(struct rq *rq, struct task_struct *t)
  */
 static inline void sched_info_depart(struct rq *rq, struct task_struct *t)
 {
-	unsigned long long delta = rq_clock(rq) -
-					t->sched_info.last_arrival;
+	unsigned long long delta = rq_clock(rq) - t->sched_info.last_arrival;
 
 	rq_sched_info_depart(rq, delta);
 
@@ -142,11 +136,10 @@ static inline void sched_info_depart(struct rq *rq, struct task_struct *t)
  * the idle task.)  We are only called when prev != next.
  */
 static inline void
-__sched_info_switch(struct rq *rq,
-		    struct task_struct *prev, struct task_struct *next)
+__sched_info_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next)
 {
 	/*
-	 * prev now departs the cpu.  It's not interesting to record
+	 * prev now departs the CPU.  It's not interesting to record
 	 * stats about how efficient we were at scheduling the idle
 	 * process, however.
 	 */
@@ -156,18 +149,19 @@ __sched_info_switch(struct rq *rq,
 	if (next != rq->idle)
 		sched_info_arrive(rq, next);
 }
+
 static inline void
-sched_info_switch(struct rq *rq,
-		  struct task_struct *prev, struct task_struct *next)
+sched_info_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next)
 {
 	if (unlikely(sched_info_on()))
 		__sched_info_switch(rq, prev, next);
 }
-#else
-#define sched_info_queued(rq, t)		do { } while (0)
-#define sched_info_reset_dequeued(t)	do { } while (0)
-#define sched_info_dequeued(rq, t)		do { } while (0)
-#define sched_info_depart(rq, t)		do { } while (0)
-#define sched_info_arrive(rq, next)		do { } while (0)
-#define sched_info_switch(rq, t, next)		do { } while (0)
+
+#else /* !CONFIG_SCHED_INFO: */
+# define sched_info_queued(rq, t)	do { } while (0)
+# define sched_info_reset_dequeued(t)	do { } while (0)
+# define sched_info_dequeued(rq, t)	do { } while (0)
+# define sched_info_depart(rq, t)	do { } while (0)
+# define sched_info_arrive(rq, next)	do { } while (0)
+# define sched_info_switch(rq, t, next)	do { } while (0)
 #endif /* CONFIG_SCHED_INFO */

kernel/sched/stop_task.c

 // SPDX-License-Identifier: GPL-2.0
-#include "sched.h"
-
 /*
  * stop-task scheduling class.
  *
@@ -9,6 +7,7 @@
  *
  * See kernel/stop_machine.c
  */
+#include "sched.h"
 
 #ifdef CONFIG_SMP
 static int
@@ -75,6 +74,14 @@ static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
 	cgroup_account_cputime(curr, delta_exec);
 }
 
+/*
+ * scheduler tick hitting a task of our scheduling class.
+ *
+ * NOTE: This function can be called remotely by the tick offload that
+ * goes along full dynticks. Therefore no local assumption can be made
+ * and everything must be accessed through the @rq and @curr passed in
+ * parameters.
+ */
 static void task_tick_stop(struct rq *rq, struct task_struct *curr, int queued)
 {
 }

kernel/sched/swait.c

 // SPDX-License-Identifier: GPL-2.0
-#include <linux/sched/signal.h>
-#include <linux/swait.h>
+/*
+ * <linux/swait.h> (simple wait queues ) implementation:
+ */
+#include "sched.h"
 
 void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
 			     struct lock_class_key *key)