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-rw-r--r--kernel/sched/core.c8493
1 files changed, 8493 insertions, 0 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
new file mode 100644
index 000000000..40f40f359
--- /dev/null
+++ b/kernel/sched/core.c
@@ -0,0 +1,8493 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kernel/sched/core.c
+ *
+ * Core kernel scheduler code and related syscalls
+ *
+ * Copyright (C) 1991-2002 Linus Torvalds
+ */
+#define CREATE_TRACE_POINTS
+#include <trace/events/sched.h>
+#undef CREATE_TRACE_POINTS
+
+#include "sched.h"
+
+#include <linux/nospec.h>
+
+#include <linux/kcov.h>
+#include <linux/scs.h>
+
+#include <asm/switch_to.h>
+#include <asm/tlb.h>
+
+#include "../workqueue_internal.h"
+#include "../../io_uring/io-wq.h"
+#include "../smpboot.h"
+
+#include "pelt.h"
+#include "smp.h"
+
+/*
+ * Export tracepoints that act as a bare tracehook (ie: have no trace event
+ * associated with them) to allow external modules to probe them.
+ */
+EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_thermal_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
+EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
+
+DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
+
+#ifdef CONFIG_SCHED_DEBUG
+/*
+ * Debugging: various feature bits
+ *
+ * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
+ * sysctl_sched_features, defined in sched.h, to allow constants propagation
+ * at compile time and compiler optimization based on features default.
+ */
+#define SCHED_FEAT(name, enabled) \
+ (1UL << __SCHED_FEAT_##name) * enabled |
+const_debug unsigned int sysctl_sched_features =
+#include "features.h"
+ 0;
+#undef SCHED_FEAT
+#endif
+
+/*
+ * Number of tasks to iterate in a single balance run.
+ * Limited because this is done with IRQs disabled.
+ */
+const_debug unsigned int sysctl_sched_nr_migrate = 32;
+
+/*
+ * period over which we measure -rt task CPU usage in us.
+ * default: 1s
+ */
+unsigned int sysctl_sched_rt_period = 1000000;
+
+__read_mostly int scheduler_running;
+
+/*
+ * part of the period that we allow rt tasks to run in us.
+ * default: 0.95s
+ */
+int sysctl_sched_rt_runtime = 950000;
+
+
+/*
+ * Serialization rules:
+ *
+ * Lock order:
+ *
+ * p->pi_lock
+ * rq->lock
+ * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls)
+ *
+ * rq1->lock
+ * rq2->lock where: rq1 < rq2
+ *
+ * Regular state:
+ *
+ * Normal scheduling state is serialized by rq->lock. __schedule() takes the
+ * local CPU's rq->lock, it optionally removes the task from the runqueue and
+ * always looks at the local rq data structures to find the most elegible task
+ * to run next.
+ *
+ * Task enqueue is also under rq->lock, possibly taken from another CPU.
+ * Wakeups from another LLC domain might use an IPI to transfer the enqueue to
+ * the local CPU to avoid bouncing the runqueue state around [ see
+ * ttwu_queue_wakelist() ]
+ *
+ * Task wakeup, specifically wakeups that involve migration, are horribly
+ * complicated to avoid having to take two rq->locks.
+ *
+ * Special state:
+ *
+ * System-calls and anything external will use task_rq_lock() which acquires
+ * both p->pi_lock and rq->lock. As a consequence the state they change is
+ * stable while holding either lock:
+ *
+ * - sched_setaffinity()/
+ * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed
+ * - set_user_nice(): p->se.load, p->*prio
+ * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio,
+ * p->se.load, p->rt_priority,
+ * p->dl.dl_{runtime, deadline, period, flags, bw, density}
+ * - sched_setnuma(): p->numa_preferred_nid
+ * - sched_move_task()/
+ * cpu_cgroup_fork(): p->sched_task_group
+ * - uclamp_update_active() p->uclamp*
+ *
+ * p->state <- TASK_*:
+ *
+ * is changed locklessly using set_current_state(), __set_current_state() or
+ * set_special_state(), see their respective comments, or by
+ * try_to_wake_up(). This latter uses p->pi_lock to serialize against
+ * concurrent self.
+ *
+ * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }:
+ *
+ * is set by activate_task() and cleared by deactivate_task(), under
+ * rq->lock. Non-zero indicates the task is runnable, the special
+ * ON_RQ_MIGRATING state is used for migration without holding both
+ * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
+ *
+ * p->on_cpu <- { 0, 1 }:
+ *
+ * is set by prepare_task() and cleared by finish_task() such that it will be
+ * set before p is scheduled-in and cleared after p is scheduled-out, both
+ * under rq->lock. Non-zero indicates the task is running on its CPU.
+ *
+ * [ The astute reader will observe that it is possible for two tasks on one
+ * CPU to have ->on_cpu = 1 at the same time. ]
+ *
+ * task_cpu(p): is changed by set_task_cpu(), the rules are:
+ *
+ * - Don't call set_task_cpu() on a blocked task:
+ *
+ * We don't care what CPU we're not running on, this simplifies hotplug,
+ * the CPU assignment of blocked tasks isn't required to be valid.
+ *
+ * - for try_to_wake_up(), called under p->pi_lock:
+ *
+ * This allows try_to_wake_up() to only take one rq->lock, see its comment.
+ *
+ * - for migration called under rq->lock:
+ * [ see task_on_rq_migrating() in task_rq_lock() ]
+ *
+ * o move_queued_task()
+ * o detach_task()
+ *
+ * - for migration called under double_rq_lock():
+ *
+ * o __migrate_swap_task()
+ * o push_rt_task() / pull_rt_task()
+ * o push_dl_task() / pull_dl_task()
+ * o dl_task_offline_migration()
+ *
+ */
+
+/*
+ * __task_rq_lock - lock the rq @p resides on.
+ */
+struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
+ __acquires(rq->lock)
+{
+ struct rq *rq;
+
+ lockdep_assert_held(&p->pi_lock);
+
+ for (;;) {
+ rq = task_rq(p);
+ raw_spin_lock(&rq->lock);
+ if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
+ rq_pin_lock(rq, rf);
+ return rq;
+ }
+ raw_spin_unlock(&rq->lock);
+
+ while (unlikely(task_on_rq_migrating(p)))
+ cpu_relax();
+ }
+}
+
+/*
+ * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
+ */
+struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
+ __acquires(p->pi_lock)
+ __acquires(rq->lock)
+{
+ struct rq *rq;
+
+ for (;;) {
+ raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
+ rq = task_rq(p);
+ raw_spin_lock(&rq->lock);
+ /*
+ * move_queued_task() task_rq_lock()
+ *
+ * ACQUIRE (rq->lock)
+ * [S] ->on_rq = MIGRATING [L] rq = task_rq()
+ * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
+ * [S] ->cpu = new_cpu [L] task_rq()
+ * [L] ->on_rq
+ * RELEASE (rq->lock)
+ *
+ * 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 address
+ * dependency headed by '[L] rq = task_rq()' and the acquire
+ * will pair with the WMB to ensure we then also see migrating.
+ */
+ if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
+ rq_pin_lock(rq, rf);
+ return rq;
+ }
+ raw_spin_unlock(&rq->lock);
+ raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
+
+ while (unlikely(task_on_rq_migrating(p)))
+ cpu_relax();
+ }
+}
+
+/*
+ * RQ-clock updating methods:
+ */
+
+static void update_rq_clock_task(struct rq *rq, s64 delta)
+{
+/*
+ * In theory, the compile should just see 0 here, and optimize out the call
+ * to sched_rt_avg_update. But I don't trust it...
+ */
+ s64 __maybe_unused steal = 0, irq_delta = 0;
+
+#ifdef CONFIG_IRQ_TIME_ACCOUNTING
+ irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
+
+ /*
+ * Since irq_time is only updated on {soft,}irq_exit, we might run into
+ * this case when a previous update_rq_clock() happened inside a
+ * {soft,}irq region.
+ *
+ * When this happens, we stop ->clock_task and only update the
+ * prev_irq_time stamp to account for the part that fit, so that a next
+ * update will consume the rest. This ensures ->clock_task is
+ * monotonic.
+ *
+ * It does however cause some slight miss-attribution of {soft,}irq
+ * time, a more accurate solution would be to update the irq_time using
+ * the current rq->clock timestamp, except that would require using
+ * atomic ops.
+ */
+ if (irq_delta > delta)
+ irq_delta = delta;
+
+ rq->prev_irq_time += irq_delta;
+ delta -= irq_delta;
+#endif
+#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
+ if (static_key_false((&paravirt_steal_rq_enabled))) {
+ steal = paravirt_steal_clock(cpu_of(rq));
+ steal -= rq->prev_steal_time_rq;
+
+ if (unlikely(steal > delta))
+ steal = delta;
+
+ rq->prev_steal_time_rq += steal;
+ delta -= steal;
+ }
+#endif
+
+ rq->clock_task += delta;
+
+#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
+ if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
+ update_irq_load_avg(rq, irq_delta + steal);
+#endif
+ update_rq_clock_pelt(rq, delta);
+}
+
+void update_rq_clock(struct rq *rq)
+{
+ s64 delta;
+
+ lockdep_assert_held(&rq->lock);
+
+ if (rq->clock_update_flags & RQCF_ACT_SKIP)
+ return;
+
+#ifdef CONFIG_SCHED_DEBUG
+ if (sched_feat(WARN_DOUBLE_CLOCK))
+ SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
+ rq->clock_update_flags |= RQCF_UPDATED;
+#endif
+
+ delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
+ if (delta < 0)
+ return;
+ rq->clock += delta;
+ update_rq_clock_task(rq, delta);
+}
+
+static inline void
+rq_csd_init(struct rq *rq, struct __call_single_data *csd, smp_call_func_t func)
+{
+ csd->flags = 0;
+ csd->func = func;
+ csd->info = rq;
+}
+
+#ifdef CONFIG_SCHED_HRTICK
+/*
+ * Use HR-timers to deliver accurate preemption points.
+ */
+
+static void hrtick_clear(struct rq *rq)
+{
+ if (hrtimer_active(&rq->hrtick_timer))
+ hrtimer_cancel(&rq->hrtick_timer);
+}
+
+/*
+ * High-resolution timer tick.
+ * Runs from hardirq context with interrupts disabled.
+ */
+static enum hrtimer_restart hrtick(struct hrtimer *timer)
+{
+ struct rq *rq = container_of(timer, struct rq, hrtick_timer);
+ struct rq_flags rf;
+
+ WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
+
+ rq_lock(rq, &rf);
+ update_rq_clock(rq);
+ rq->curr->sched_class->task_tick(rq, rq->curr, 1);
+ rq_unlock(rq, &rf);
+
+ return HRTIMER_NORESTART;
+}
+
+#ifdef CONFIG_SMP
+
+static void __hrtick_restart(struct rq *rq)
+{
+ struct hrtimer *timer = &rq->hrtick_timer;
+ ktime_t time = rq->hrtick_time;
+
+ hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD);
+}
+
+/*
+ * called from hardirq (IPI) context
+ */
+static void __hrtick_start(void *arg)
+{
+ struct rq *rq = arg;
+ struct rq_flags rf;
+
+ rq_lock(rq, &rf);
+ __hrtick_restart(rq);
+ rq_unlock(rq, &rf);
+}
+
+/*
+ * Called to set the hrtick timer state.
+ *
+ * called with rq->lock held and irqs disabled
+ */
+void hrtick_start(struct rq *rq, u64 delay)
+{
+ struct hrtimer *timer = &rq->hrtick_timer;
+ s64 delta;
+
+ /*
+ * Don't schedule slices shorter than 10000ns, that just
+ * doesn't make sense and can cause timer DoS.
+ */
+ delta = max_t(s64, delay, 10000LL);
+ rq->hrtick_time = ktime_add_ns(timer->base->get_time(), delta);
+
+ if (rq == this_rq())
+ __hrtick_restart(rq);
+ else
+ smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
+}
+
+#else
+/*
+ * Called to set the hrtick timer state.
+ *
+ * called with rq->lock held and irqs disabled
+ */
+void hrtick_start(struct rq *rq, u64 delay)
+{
+ /*
+ * Don't schedule slices shorter than 10000ns, that just
+ * doesn't make sense. Rely on vruntime for fairness.
+ */
+ delay = max_t(u64, delay, 10000LL);
+ hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
+ HRTIMER_MODE_REL_PINNED_HARD);
+}
+
+#endif /* CONFIG_SMP */
+
+static void hrtick_rq_init(struct rq *rq)
+{
+#ifdef CONFIG_SMP
+ rq_csd_init(rq, &rq->hrtick_csd, __hrtick_start);
+#endif
+ hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
+ rq->hrtick_timer.function = hrtick;
+}
+#else /* CONFIG_SCHED_HRTICK */
+static inline void hrtick_clear(struct rq *rq)
+{
+}
+
+static inline void hrtick_rq_init(struct rq *rq)
+{
+}
+#endif /* CONFIG_SCHED_HRTICK */
+
+/*
+ * cmpxchg based fetch_or, macro so it works for different integer types
+ */
+#define fetch_or(ptr, mask) \
+ ({ \
+ typeof(ptr) _ptr = (ptr); \
+ typeof(mask) _mask = (mask); \
+ typeof(*_ptr) _old, _val = *_ptr; \
+ \
+ for (;;) { \
+ _old = cmpxchg(_ptr, _val, _val | _mask); \
+ if (_old == _val) \
+ break; \
+ _val = _old; \
+ } \
+ _old; \
+})
+
+#if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
+/*
+ * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
+ * this avoids any races wrt polling state changes and thereby avoids
+ * spurious IPIs.
+ */
+static bool set_nr_and_not_polling(struct task_struct *p)
+{
+ struct thread_info *ti = task_thread_info(p);
+ return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
+}
+
+/*
+ * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
+ *
+ * If this returns true, then the idle task promises to call
+ * sched_ttwu_pending() and reschedule soon.
+ */
+static bool set_nr_if_polling(struct task_struct *p)
+{
+ struct thread_info *ti = task_thread_info(p);
+ typeof(ti->flags) old, val = READ_ONCE(ti->flags);
+
+ for (;;) {
+ if (!(val & _TIF_POLLING_NRFLAG))
+ return false;
+ if (val & _TIF_NEED_RESCHED)
+ return true;
+ old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
+ if (old == val)
+ break;
+ val = old;
+ }
+ return true;
+}
+
+#else
+static bool set_nr_and_not_polling(struct task_struct *p)
+{
+ set_tsk_need_resched(p);
+ return true;
+}
+
+#ifdef CONFIG_SMP
+static bool set_nr_if_polling(struct task_struct *p)
+{
+ return false;
+}
+#endif
+#endif
+
+static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task)
+{
+ struct wake_q_node *node = &task->wake_q;
+
+ /*
+ * Atomically grab the task, if ->wake_q is !nil already it means
+ * its already queued (either by us or someone else) and will get the
+ * wakeup due to that.
+ *
+ * In order to ensure that a pending wakeup will observe our pending
+ * state, even in the failed case, an explicit smp_mb() must be used.
+ */
+ smp_mb__before_atomic();
+ if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL)))
+ return false;
+
+ /*
+ * The head is context local, there can be no concurrency.
+ */
+ *head->lastp = node;
+ head->lastp = &node->next;
+ return true;
+}
+
+/**
+ * wake_q_add() - queue a wakeup for 'later' waking.
+ * @head: the wake_q_head to add @task to
+ * @task: the task to queue for 'later' wakeup
+ *
+ * Queue a task for later wakeup, most likely by the wake_up_q() call in the
+ * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
+ * instantly.
+ *
+ * This function must be used as-if it were wake_up_process(); IOW the task
+ * must be ready to be woken at this location.
+ */
+void wake_q_add(struct wake_q_head *head, struct task_struct *task)
+{
+ if (__wake_q_add(head, task))
+ get_task_struct(task);
+}
+
+/**
+ * wake_q_add_safe() - safely queue a wakeup for 'later' waking.
+ * @head: the wake_q_head to add @task to
+ * @task: the task to queue for 'later' wakeup
+ *
+ * Queue a task for later wakeup, most likely by the wake_up_q() call in the
+ * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
+ * instantly.
+ *
+ * This function must be used as-if it were wake_up_process(); IOW the task
+ * must be ready to be woken at this location.
+ *
+ * This function is essentially a task-safe equivalent to wake_q_add(). Callers
+ * that already hold reference to @task can call the 'safe' version and trust
+ * wake_q to do the right thing depending whether or not the @task is already
+ * queued for wakeup.
+ */
+void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
+{
+ if (!__wake_q_add(head, task))
+ put_task_struct(task);
+}
+
+void wake_up_q(struct wake_q_head *head)
+{
+ struct wake_q_node *node = head->first;
+
+ while (node != WAKE_Q_TAIL) {
+ struct task_struct *task;
+
+ task = container_of(node, struct task_struct, wake_q);
+ BUG_ON(!task);
+ /* Task can safely be re-inserted now: */
+ node = node->next;
+ task->wake_q.next = NULL;
+
+ /*
+ * wake_up_process() executes a full barrier, which pairs with
+ * the queueing in wake_q_add() so as not to miss wakeups.
+ */
+ wake_up_process(task);
+ put_task_struct(task);
+ }
+}
+
+/*
+ * resched_curr - mark rq's current task 'to be rescheduled now'.
+ *
+ * On UP this means the setting of the need_resched flag, on SMP it
+ * might also involve a cross-CPU call to trigger the scheduler on
+ * the target CPU.
+ */
+void resched_curr(struct rq *rq)
+{
+ struct task_struct *curr = rq->curr;
+ int cpu;
+
+ lockdep_assert_held(&rq->lock);
+
+ if (test_tsk_need_resched(curr))
+ return;
+
+ cpu = cpu_of(rq);
+
+ if (cpu == smp_processor_id()) {
+ set_tsk_need_resched(curr);
+ set_preempt_need_resched();
+ return;
+ }
+
+ if (set_nr_and_not_polling(curr))
+ smp_send_reschedule(cpu);
+ else
+ trace_sched_wake_idle_without_ipi(cpu);
+}
+
+void resched_cpu(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&rq->lock, flags);
+ if (cpu_online(cpu) || cpu == smp_processor_id())
+ resched_curr(rq);
+ raw_spin_unlock_irqrestore(&rq->lock, flags);
+}
+
+#ifdef CONFIG_SMP
+#ifdef CONFIG_NO_HZ_COMMON
+/*
+ * In the semi idle case, use the nearest busy CPU for migrating timers
+ * from an idle CPU. This is good for power-savings.
+ *
+ * We don't do similar optimization for completely idle system, as
+ * selecting an idle CPU will add more delays to the timers than intended
+ * (as that CPU's timer base may not be uptodate wrt jiffies etc).
+ */
+int get_nohz_timer_target(void)
+{
+ int i, cpu = smp_processor_id(), default_cpu = -1;
+ struct sched_domain *sd;
+
+ if (housekeeping_cpu(cpu, HK_FLAG_TIMER)) {
+ if (!idle_cpu(cpu))
+ return cpu;
+ default_cpu = cpu;
+ }
+
+ rcu_read_lock();
+ for_each_domain(cpu, sd) {
+ for_each_cpu_and(i, sched_domain_span(sd),
+ housekeeping_cpumask(HK_FLAG_TIMER)) {
+ if (cpu == i)
+ continue;
+
+ if (!idle_cpu(i)) {
+ cpu = i;
+ goto unlock;
+ }
+ }
+ }
+
+ if (default_cpu == -1)
+ default_cpu = housekeeping_any_cpu(HK_FLAG_TIMER);
+ cpu = default_cpu;
+unlock:
+ rcu_read_unlock();
+ return cpu;
+}
+
+/*
+ * When add_timer_on() enqueues a timer into the timer wheel of an
+ * idle CPU then this timer might expire before the next timer event
+ * which is scheduled to wake up that CPU. In case of a completely
+ * idle system the next event might even be infinite time into the
+ * future. wake_up_idle_cpu() ensures that the CPU is woken up and
+ * leaves the inner idle loop so the newly added timer is taken into
+ * account when the CPU goes back to idle and evaluates the timer
+ * wheel for the next timer event.
+ */
+static void wake_up_idle_cpu(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ if (cpu == smp_processor_id())
+ return;
+
+ if (set_nr_and_not_polling(rq->idle))
+ smp_send_reschedule(cpu);
+ else
+ trace_sched_wake_idle_without_ipi(cpu);
+}
+
+static bool wake_up_full_nohz_cpu(int cpu)
+{
+ /*
+ * We just need the target to call irq_exit() and re-evaluate
+ * the next tick. The nohz full kick at least implies that.
+ * If needed we can still optimize that later with an
+ * empty IRQ.
+ */
+ if (cpu_is_offline(cpu))
+ return true; /* Don't try to wake offline CPUs. */
+ if (tick_nohz_full_cpu(cpu)) {
+ if (cpu != smp_processor_id() ||
+ tick_nohz_tick_stopped())
+ tick_nohz_full_kick_cpu(cpu);
+ return true;
+ }
+
+ return false;
+}
+
+/*
+ * Wake up the specified CPU. If the CPU is going offline, it is the
+ * caller's responsibility to deal with the lost wakeup, for example,
+ * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
+ */
+void wake_up_nohz_cpu(int cpu)
+{
+ if (!wake_up_full_nohz_cpu(cpu))
+ wake_up_idle_cpu(cpu);
+}
+
+static void nohz_csd_func(void *info)
+{
+ struct rq *rq = info;
+ int cpu = cpu_of(rq);
+ unsigned int flags;
+
+ /*
+ * Release the rq::nohz_csd.
+ */
+ flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(cpu));
+ WARN_ON(!(flags & NOHZ_KICK_MASK));
+
+ rq->idle_balance = idle_cpu(cpu);
+ if (rq->idle_balance && !need_resched()) {
+ rq->nohz_idle_balance = flags;
+ raise_softirq_irqoff(SCHED_SOFTIRQ);
+ }
+}
+
+#endif /* CONFIG_NO_HZ_COMMON */
+
+#ifdef CONFIG_NO_HZ_FULL
+bool sched_can_stop_tick(struct rq *rq)
+{
+ int fifo_nr_running;
+
+ /* Deadline tasks, even if single, need the tick */
+ if (rq->dl.dl_nr_running)
+ return false;
+
+ /*
+ * If there are more than one RR tasks, we need the tick to effect the
+ * actual RR behaviour.
+ */
+ if (rq->rt.rr_nr_running) {
+ if (rq->rt.rr_nr_running == 1)
+ return true;
+ else
+ return false;
+ }
+
+ /*
+ * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
+ * forced preemption between FIFO tasks.
+ */
+ fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
+ if (fifo_nr_running)
+ return true;
+
+ /*
+ * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
+ * if there's more than one we need the tick for involuntary
+ * preemption.
+ */
+ if (rq->nr_running > 1)
+ return false;
+
+ return true;
+}
+#endif /* CONFIG_NO_HZ_FULL */
+#endif /* CONFIG_SMP */
+
+#if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
+ (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
+/*
+ * Iterate task_group tree rooted at *from, calling @down when first entering a
+ * node and @up when leaving it for the final time.
+ *
+ * Caller must hold rcu_lock or sufficient equivalent.
+ */
+int walk_tg_tree_from(struct task_group *from,
+ tg_visitor down, tg_visitor up, void *data)
+{
+ struct task_group *parent, *child;
+ int ret;
+
+ parent = from;
+
+down:
+ ret = (*down)(parent, data);
+ if (ret)
+ goto out;
+ list_for_each_entry_rcu(child, &parent->children, siblings) {
+ parent = child;
+ goto down;
+
+up:
+ continue;
+ }
+ ret = (*up)(parent, data);
+ if (ret || parent == from)
+ goto out;
+
+ child = parent;
+ parent = parent->parent;
+ if (parent)
+ goto up;
+out:
+ return ret;
+}
+
+int tg_nop(struct task_group *tg, void *data)
+{
+ return 0;
+}
+#endif
+
+static void set_load_weight(struct task_struct *p)
+{
+ bool update_load = !(READ_ONCE(p->state) & TASK_NEW);
+ int prio = p->static_prio - MAX_RT_PRIO;
+ struct load_weight *load = &p->se.load;
+
+ /*
+ * SCHED_IDLE tasks get minimal weight:
+ */
+ if (task_has_idle_policy(p)) {
+ load->weight = scale_load(WEIGHT_IDLEPRIO);
+ load->inv_weight = WMULT_IDLEPRIO;
+ return;
+ }
+
+ /*
+ * SCHED_OTHER tasks have to update their load when changing their
+ * weight
+ */
+ if (update_load && p->sched_class == &fair_sched_class) {
+ reweight_task(p, prio);
+ } else {
+ load->weight = scale_load(sched_prio_to_weight[prio]);
+ load->inv_weight = sched_prio_to_wmult[prio];
+ }
+}
+
+#ifdef CONFIG_UCLAMP_TASK
+/*
+ * Serializes updates of utilization clamp values
+ *
+ * The (slow-path) user-space triggers utilization clamp value updates which
+ * can require updates on (fast-path) scheduler's data structures used to
+ * support enqueue/dequeue operations.
+ * While the per-CPU rq lock protects fast-path update operations, user-space
+ * requests are serialized using a mutex to reduce the risk of conflicting
+ * updates or API abuses.
+ */
+static DEFINE_MUTEX(uclamp_mutex);
+
+/* Max allowed minimum utilization */
+unsigned int sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE;
+
+/* Max allowed maximum utilization */
+unsigned int sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE;
+
+/*
+ * By default RT tasks run at the maximum performance point/capacity of the
+ * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to
+ * SCHED_CAPACITY_SCALE.
+ *
+ * This knob allows admins to change the default behavior when uclamp is being
+ * used. In battery powered devices, particularly, running at the maximum
+ * capacity and frequency will increase energy consumption and shorten the
+ * battery life.
+ *
+ * This knob only affects RT tasks that their uclamp_se->user_defined == false.
+ *
+ * This knob will not override the system default sched_util_clamp_min defined
+ * above.
+ */
+unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE;
+
+/* All clamps are required to be less or equal than these values */
+static struct uclamp_se uclamp_default[UCLAMP_CNT];
+
+/*
+ * This static key is used to reduce the uclamp overhead in the fast path. It
+ * primarily disables the call to uclamp_rq_{inc, dec}() in
+ * enqueue/dequeue_task().
+ *
+ * This allows users to continue to enable uclamp in their kernel config with
+ * minimum uclamp overhead in the fast path.
+ *
+ * As soon as userspace modifies any of the uclamp knobs, the static key is
+ * enabled, since we have an actual users that make use of uclamp
+ * functionality.
+ *
+ * The knobs that would enable this static key are:
+ *
+ * * A task modifying its uclamp value with sched_setattr().
+ * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs.
+ * * An admin modifying the cgroup cpu.uclamp.{min, max}
+ */
+DEFINE_STATIC_KEY_FALSE(sched_uclamp_used);
+
+/* Integer rounded range for each bucket */
+#define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS)
+
+#define for_each_clamp_id(clamp_id) \
+ for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++)
+
+static inline unsigned int uclamp_bucket_id(unsigned int clamp_value)
+{
+ return min_t(unsigned int, clamp_value / UCLAMP_BUCKET_DELTA, UCLAMP_BUCKETS - 1);
+}
+
+static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
+{
+ if (clamp_id == UCLAMP_MIN)
+ return 0;
+ return SCHED_CAPACITY_SCALE;
+}
+
+static inline void uclamp_se_set(struct uclamp_se *uc_se,
+ unsigned int value, bool user_defined)
+{
+ uc_se->value = value;
+ uc_se->bucket_id = uclamp_bucket_id(value);
+ uc_se->user_defined = user_defined;
+}
+
+static inline unsigned int
+uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id,
+ unsigned int clamp_value)
+{
+ /*
+ * Avoid blocked utilization pushing up the frequency when we go
+ * idle (which drops the max-clamp) by retaining the last known
+ * max-clamp.
+ */
+ if (clamp_id == UCLAMP_MAX) {
+ rq->uclamp_flags |= UCLAMP_FLAG_IDLE;
+ return clamp_value;
+ }
+
+ return uclamp_none(UCLAMP_MIN);
+}
+
+static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
+ unsigned int clamp_value)
+{
+ /* Reset max-clamp retention only on idle exit */
+ if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
+ return;
+
+ uclamp_rq_set(rq, clamp_id, clamp_value);
+}
+
+static inline
+unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
+ unsigned int clamp_value)
+{
+ struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
+ int bucket_id = UCLAMP_BUCKETS - 1;
+
+ /*
+ * Since both min and max clamps are max aggregated, find the
+ * top most bucket with tasks in.
+ */
+ for ( ; bucket_id >= 0; bucket_id--) {
+ if (!bucket[bucket_id].tasks)
+ continue;
+ return bucket[bucket_id].value;
+ }
+
+ /* No tasks -- default clamp values */
+ return uclamp_idle_value(rq, clamp_id, clamp_value);
+}
+
+static void __uclamp_update_util_min_rt_default(struct task_struct *p)
+{
+ unsigned int default_util_min;
+ struct uclamp_se *uc_se;
+
+ lockdep_assert_held(&p->pi_lock);
+
+ uc_se = &p->uclamp_req[UCLAMP_MIN];
+
+ /* Only sync if user didn't override the default */
+ if (uc_se->user_defined)
+ return;
+
+ default_util_min = sysctl_sched_uclamp_util_min_rt_default;
+ uclamp_se_set(uc_se, default_util_min, false);
+}
+
+static void uclamp_update_util_min_rt_default(struct task_struct *p)
+{
+ struct rq_flags rf;
+ struct rq *rq;
+
+ if (!rt_task(p))
+ return;
+
+ /* Protect updates to p->uclamp_* */
+ rq = task_rq_lock(p, &rf);
+ __uclamp_update_util_min_rt_default(p);
+ task_rq_unlock(rq, p, &rf);
+}
+
+static void uclamp_sync_util_min_rt_default(void)
+{
+ struct task_struct *g, *p;
+
+ /*
+ * copy_process() sysctl_uclamp
+ * uclamp_min_rt = X;
+ * write_lock(&tasklist_lock) read_lock(&tasklist_lock)
+ * // link thread smp_mb__after_spinlock()
+ * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock);
+ * sched_post_fork() for_each_process_thread()
+ * __uclamp_sync_rt() __uclamp_sync_rt()
+ *
+ * Ensures that either sched_post_fork() will observe the new
+ * uclamp_min_rt or for_each_process_thread() will observe the new
+ * task.
+ */
+ read_lock(&tasklist_lock);
+ smp_mb__after_spinlock();
+ read_unlock(&tasklist_lock);
+
+ rcu_read_lock();
+ for_each_process_thread(g, p)
+ uclamp_update_util_min_rt_default(p);
+ rcu_read_unlock();
+}
+
+static inline struct uclamp_se
+uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
+{
+ /* Copy by value as we could modify it */
+ struct uclamp_se uc_req = p->uclamp_req[clamp_id];
+#ifdef CONFIG_UCLAMP_TASK_GROUP
+ unsigned int tg_min, tg_max, value;
+
+ /*
+ * Tasks in autogroups or root task group will be
+ * restricted by system defaults.
+ */
+ if (task_group_is_autogroup(task_group(p)))
+ return uc_req;
+ if (task_group(p) == &root_task_group)
+ return uc_req;
+
+ tg_min = task_group(p)->uclamp[UCLAMP_MIN].value;
+ tg_max = task_group(p)->uclamp[UCLAMP_MAX].value;
+ value = uc_req.value;
+ value = clamp(value, tg_min, tg_max);
+ uclamp_se_set(&uc_req, value, false);
+#endif
+
+ return uc_req;
+}
+
+/*
+ * The effective clamp bucket index of a task depends on, by increasing
+ * priority:
+ * - the task specific clamp value, when explicitly requested from userspace
+ * - the task group effective clamp value, for tasks not either in the root
+ * group or in an autogroup
+ * - the system default clamp value, defined by the sysadmin
+ */
+static inline struct uclamp_se
+uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
+{
+ struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id);
+ struct uclamp_se uc_max = uclamp_default[clamp_id];
+
+ /* System default restrictions always apply */
+ if (unlikely(uc_req.value > uc_max.value))
+ return uc_max;
+
+ return uc_req;
+}
+
+unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
+{
+ struct uclamp_se uc_eff;
+
+ /* Task currently refcounted: use back-annotated (effective) value */
+ if (p->uclamp[clamp_id].active)
+ return (unsigned long)p->uclamp[clamp_id].value;
+
+ uc_eff = uclamp_eff_get(p, clamp_id);
+
+ return (unsigned long)uc_eff.value;
+}
+
+/*
+ * When a task is enqueued on a rq, the clamp bucket currently defined by the
+ * task's uclamp::bucket_id is refcounted on that rq. This also immediately
+ * updates the rq's clamp value if required.
+ *
+ * Tasks can have a task-specific value requested from user-space, track
+ * within each bucket the maximum value for tasks refcounted in it.
+ * This "local max aggregation" allows to track the exact "requested" value
+ * for each bucket when all its RUNNABLE tasks require the same clamp.
+ */
+static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
+ enum uclamp_id clamp_id)
+{
+ struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
+ struct uclamp_se *uc_se = &p->uclamp[clamp_id];
+ struct uclamp_bucket *bucket;
+
+ lockdep_assert_held(&rq->lock);
+
+ /* Update task effective clamp */
+ p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id);
+
+ bucket = &uc_rq->bucket[uc_se->bucket_id];
+ bucket->tasks++;
+ uc_se->active = true;
+
+ uclamp_idle_reset(rq, clamp_id, uc_se->value);
+
+ /*
+ * Local max aggregation: rq buckets always track the max
+ * "requested" clamp value of its RUNNABLE tasks.
+ */
+ if (bucket->tasks == 1 || uc_se->value > bucket->value)
+ bucket->value = uc_se->value;
+
+ if (uc_se->value > uclamp_rq_get(rq, clamp_id))
+ uclamp_rq_set(rq, clamp_id, uc_se->value);
+}
+
+/*
+ * When a task is dequeued from a rq, the clamp bucket refcounted by the task
+ * is released. If this is the last task reference counting the rq's max
+ * active clamp value, then the rq's clamp value is updated.
+ *
+ * Both refcounted tasks and rq's cached clamp values are expected to be
+ * always valid. If it's detected they are not, as defensive programming,
+ * enforce the expected state and warn.
+ */
+static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
+ enum uclamp_id clamp_id)
+{
+ struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
+ struct uclamp_se *uc_se = &p->uclamp[clamp_id];
+ struct uclamp_bucket *bucket;
+ unsigned int bkt_clamp;
+ unsigned int rq_clamp;
+
+ lockdep_assert_held(&rq->lock);
+
+ /*
+ * If sched_uclamp_used was enabled after task @p was enqueued,
+ * we could end up with unbalanced call to uclamp_rq_dec_id().
+ *
+ * In this case the uc_se->active flag should be false since no uclamp
+ * accounting was performed at enqueue time and we can just return
+ * here.
+ *
+ * Need to be careful of the following enqeueue/dequeue ordering
+ * problem too
+ *
+ * enqueue(taskA)
+ * // sched_uclamp_used gets enabled
+ * enqueue(taskB)
+ * dequeue(taskA)
+ * // Must not decrement bukcet->tasks here
+ * dequeue(taskB)
+ *
+ * where we could end up with stale data in uc_se and
+ * bucket[uc_se->bucket_id].
+ *
+ * The following check here eliminates the possibility of such race.
+ */
+ if (unlikely(!uc_se->active))
+ return;
+
+ bucket = &uc_rq->bucket[uc_se->bucket_id];
+
+ SCHED_WARN_ON(!bucket->tasks);
+ if (likely(bucket->tasks))
+ bucket->tasks--;
+
+ uc_se->active = false;
+
+ /*
+ * Keep "local max aggregation" simple and accept to (possibly)
+ * overboost some RUNNABLE tasks in the same bucket.
+ * The rq clamp bucket value is reset to its base value whenever
+ * there are no more RUNNABLE tasks refcounting it.
+ */
+ if (likely(bucket->tasks))
+ return;
+
+ rq_clamp = uclamp_rq_get(rq, clamp_id);
+ /*
+ * Defensive programming: this should never happen. If it happens,
+ * e.g. due to future modification, warn and fixup the expected value.
+ */
+ SCHED_WARN_ON(bucket->value > rq_clamp);
+ if (bucket->value >= rq_clamp) {
+ bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
+ uclamp_rq_set(rq, clamp_id, bkt_clamp);
+ }
+}
+
+static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
+{
+ enum uclamp_id clamp_id;
+
+ /*
+ * Avoid any overhead until uclamp is actually used by the userspace.
+ *
+ * The condition is constructed such that a NOP is generated when
+ * sched_uclamp_used is disabled.
+ */
+ if (!static_branch_unlikely(&sched_uclamp_used))
+ return;
+
+ if (unlikely(!p->sched_class->uclamp_enabled))
+ return;
+
+ for_each_clamp_id(clamp_id)
+ uclamp_rq_inc_id(rq, p, clamp_id);
+
+ /* Reset clamp idle holding when there is one RUNNABLE task */
+ if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
+ rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
+}
+
+static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
+{
+ enum uclamp_id clamp_id;
+
+ /*
+ * Avoid any overhead until uclamp is actually used by the userspace.
+ *
+ * The condition is constructed such that a NOP is generated when
+ * sched_uclamp_used is disabled.
+ */
+ if (!static_branch_unlikely(&sched_uclamp_used))
+ return;
+
+ if (unlikely(!p->sched_class->uclamp_enabled))
+ return;
+
+ for_each_clamp_id(clamp_id)
+ uclamp_rq_dec_id(rq, p, clamp_id);
+}
+
+static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p,
+ enum uclamp_id clamp_id)
+{
+ if (!p->uclamp[clamp_id].active)
+ return;
+
+ uclamp_rq_dec_id(rq, p, clamp_id);
+ uclamp_rq_inc_id(rq, p, clamp_id);
+
+ /*
+ * Make sure to clear the idle flag if we've transiently reached 0
+ * active tasks on rq.
+ */
+ if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE))
+ rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
+}
+
+static inline void
+uclamp_update_active(struct task_struct *p)
+{
+ enum uclamp_id clamp_id;
+ struct rq_flags rf;
+ struct rq *rq;
+
+ /*
+ * Lock the task and the rq where the task is (or was) queued.
+ *
+ * We might lock the (previous) rq of a !RUNNABLE task, but that's the
+ * price to pay to safely serialize util_{min,max} updates with
+ * enqueues, dequeues and migration operations.
+ * This is the same locking schema used by __set_cpus_allowed_ptr().
+ */
+ rq = task_rq_lock(p, &rf);
+
+ /*
+ * Setting the clamp bucket is serialized by task_rq_lock().
+ * If the task is not yet RUNNABLE and its task_struct is not
+ * affecting a valid clamp bucket, the next time it's enqueued,
+ * it will already see the updated clamp bucket value.
+ */
+ for_each_clamp_id(clamp_id)
+ uclamp_rq_reinc_id(rq, p, clamp_id);
+
+ task_rq_unlock(rq, p, &rf);
+}
+
+#ifdef CONFIG_UCLAMP_TASK_GROUP
+static inline void
+uclamp_update_active_tasks(struct cgroup_subsys_state *css)
+{
+ struct css_task_iter it;
+ struct task_struct *p;
+
+ css_task_iter_start(css, 0, &it);
+ while ((p = css_task_iter_next(&it)))
+ uclamp_update_active(p);
+ css_task_iter_end(&it);
+}
+
+static void cpu_util_update_eff(struct cgroup_subsys_state *css);
+static void uclamp_update_root_tg(void)
+{
+ struct task_group *tg = &root_task_group;
+
+ uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN],
+ sysctl_sched_uclamp_util_min, false);
+ uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX],
+ sysctl_sched_uclamp_util_max, false);
+
+ rcu_read_lock();
+ cpu_util_update_eff(&root_task_group.css);
+ rcu_read_unlock();
+}
+#else
+static void uclamp_update_root_tg(void) { }
+#endif
+
+int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ bool update_root_tg = false;
+ int old_min, old_max, old_min_rt;
+ int result;
+
+ mutex_lock(&uclamp_mutex);
+ old_min = sysctl_sched_uclamp_util_min;
+ old_max = sysctl_sched_uclamp_util_max;
+ old_min_rt = sysctl_sched_uclamp_util_min_rt_default;
+
+ result = proc_dointvec(table, write, buffer, lenp, ppos);
+ if (result)
+ goto undo;
+ if (!write)
+ goto done;
+
+ if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max ||
+ sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE ||
+ sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) {
+
+ result = -EINVAL;
+ goto undo;
+ }
+
+ if (old_min != sysctl_sched_uclamp_util_min) {
+ uclamp_se_set(&uclamp_default[UCLAMP_MIN],
+ sysctl_sched_uclamp_util_min, false);
+ update_root_tg = true;
+ }
+ if (old_max != sysctl_sched_uclamp_util_max) {
+ uclamp_se_set(&uclamp_default[UCLAMP_MAX],
+ sysctl_sched_uclamp_util_max, false);
+ update_root_tg = true;
+ }
+
+ if (update_root_tg) {
+ static_branch_enable(&sched_uclamp_used);
+ uclamp_update_root_tg();
+ }
+
+ if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) {
+ static_branch_enable(&sched_uclamp_used);
+ uclamp_sync_util_min_rt_default();
+ }
+
+ /*
+ * We update all RUNNABLE tasks only when task groups are in use.
+ * Otherwise, keep it simple and do just a lazy update at each next
+ * task enqueue time.
+ */
+
+ goto done;
+
+undo:
+ sysctl_sched_uclamp_util_min = old_min;
+ sysctl_sched_uclamp_util_max = old_max;
+ sysctl_sched_uclamp_util_min_rt_default = old_min_rt;
+done:
+ mutex_unlock(&uclamp_mutex);
+
+ return result;
+}
+
+static int uclamp_validate(struct task_struct *p,
+ const struct sched_attr *attr)
+{
+ unsigned int lower_bound = p->uclamp_req[UCLAMP_MIN].value;
+ unsigned int upper_bound = p->uclamp_req[UCLAMP_MAX].value;
+
+ if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN)
+ lower_bound = attr->sched_util_min;
+ if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX)
+ upper_bound = attr->sched_util_max;
+
+ if (lower_bound > upper_bound)
+ return -EINVAL;
+ if (upper_bound > SCHED_CAPACITY_SCALE)
+ return -EINVAL;
+
+ /*
+ * We have valid uclamp attributes; make sure uclamp is enabled.
+ *
+ * We need to do that here, because enabling static branches is a
+ * blocking operation which obviously cannot be done while holding
+ * scheduler locks.
+ */
+ static_branch_enable(&sched_uclamp_used);
+
+ return 0;
+}
+
+static void __setscheduler_uclamp(struct task_struct *p,
+ const struct sched_attr *attr)
+{
+ enum uclamp_id clamp_id;
+
+ /*
+ * On scheduling class change, reset to default clamps for tasks
+ * without a task-specific value.
+ */
+ for_each_clamp_id(clamp_id) {
+ struct uclamp_se *uc_se = &p->uclamp_req[clamp_id];
+
+ /* Keep using defined clamps across class changes */
+ if (uc_se->user_defined)
+ continue;
+
+ /*
+ * RT by default have a 100% boost value that could be modified
+ * at runtime.
+ */
+ if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
+ __uclamp_update_util_min_rt_default(p);
+ else
+ uclamp_se_set(uc_se, uclamp_none(clamp_id), false);
+
+ }
+
+ if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)))
+ return;
+
+ if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
+ uclamp_se_set(&p->uclamp_req[UCLAMP_MIN],
+ attr->sched_util_min, true);
+ }
+
+ if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
+ uclamp_se_set(&p->uclamp_req[UCLAMP_MAX],
+ attr->sched_util_max, true);
+ }
+}
+
+static void uclamp_fork(struct task_struct *p)
+{
+ enum uclamp_id clamp_id;
+
+ /*
+ * We don't need to hold task_rq_lock() when updating p->uclamp_* here
+ * as the task is still at its early fork stages.
+ */
+ for_each_clamp_id(clamp_id)
+ p->uclamp[clamp_id].active = false;
+
+ if (likely(!p->sched_reset_on_fork))
+ return;
+
+ for_each_clamp_id(clamp_id) {
+ uclamp_se_set(&p->uclamp_req[clamp_id],
+ uclamp_none(clamp_id), false);
+ }
+}
+
+static void uclamp_post_fork(struct task_struct *p)
+{
+ uclamp_update_util_min_rt_default(p);
+}
+
+static void __init init_uclamp_rq(struct rq *rq)
+{
+ enum uclamp_id clamp_id;
+ struct uclamp_rq *uc_rq = rq->uclamp;
+
+ for_each_clamp_id(clamp_id) {
+ uc_rq[clamp_id] = (struct uclamp_rq) {
+ .value = uclamp_none(clamp_id)
+ };
+ }
+
+ rq->uclamp_flags = UCLAMP_FLAG_IDLE;
+}
+
+static void __init init_uclamp(void)
+{
+ struct uclamp_se uc_max = {};
+ enum uclamp_id clamp_id;
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ init_uclamp_rq(cpu_rq(cpu));
+
+ for_each_clamp_id(clamp_id) {
+ uclamp_se_set(&init_task.uclamp_req[clamp_id],
+ uclamp_none(clamp_id), false);
+ }
+
+ /* System defaults allow max clamp values for both indexes */
+ uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false);
+ for_each_clamp_id(clamp_id) {
+ uclamp_default[clamp_id] = uc_max;
+#ifdef CONFIG_UCLAMP_TASK_GROUP
+ root_task_group.uclamp_req[clamp_id] = uc_max;
+ root_task_group.uclamp[clamp_id] = uc_max;
+#endif
+ }
+}
+
+#else /* CONFIG_UCLAMP_TASK */
+static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { }
+static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
+static inline int uclamp_validate(struct task_struct *p,
+ const struct sched_attr *attr)
+{
+ return -EOPNOTSUPP;
+}
+static void __setscheduler_uclamp(struct task_struct *p,
+ const struct sched_attr *attr) { }
+static inline void uclamp_fork(struct task_struct *p) { }
+static inline void uclamp_post_fork(struct task_struct *p) { }
+static inline void init_uclamp(void) { }
+#endif /* CONFIG_UCLAMP_TASK */
+
+static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
+{
+ if (!(flags & ENQUEUE_NOCLOCK))
+ update_rq_clock(rq);
+
+ if (!(flags & ENQUEUE_RESTORE)) {
+ sched_info_queued(rq, p);
+ psi_enqueue(p, flags & ENQUEUE_WAKEUP);
+ }
+
+ uclamp_rq_inc(rq, p);
+ p->sched_class->enqueue_task(rq, p, flags);
+}
+
+static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
+{
+ if (!(flags & DEQUEUE_NOCLOCK))
+ update_rq_clock(rq);
+
+ if (!(flags & DEQUEUE_SAVE)) {
+ sched_info_dequeued(rq, p);
+ psi_dequeue(p, flags & DEQUEUE_SLEEP);
+ }
+
+ uclamp_rq_dec(rq, p);
+ p->sched_class->dequeue_task(rq, p, flags);
+}
+
+void activate_task(struct rq *rq, struct task_struct *p, int flags)
+{
+ if (task_on_rq_migrating(p))
+ flags |= ENQUEUE_MIGRATED;
+
+ enqueue_task(rq, p, flags);
+
+ p->on_rq = TASK_ON_RQ_QUEUED;
+}
+
+void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
+{
+ p->on_rq = (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING;
+
+ dequeue_task(rq, p, flags);
+}
+
+static inline int __normal_prio(int policy, int rt_prio, int nice)
+{
+ int prio;
+
+ if (dl_policy(policy))
+ prio = MAX_DL_PRIO - 1;
+ else if (rt_policy(policy))
+ prio = MAX_RT_PRIO - 1 - rt_prio;
+ else
+ prio = NICE_TO_PRIO(nice);
+
+ return prio;
+}
+
+/*
+ * Calculate the expected normal priority: i.e. priority
+ * without taking RT-inheritance into account. Might be
+ * boosted by interactivity modifiers. Changes upon fork,
+ * setprio syscalls, and whenever the interactivity
+ * estimator recalculates.
+ */
+static inline int normal_prio(struct task_struct *p)
+{
+ return __normal_prio(p->policy, p->rt_priority, PRIO_TO_NICE(p->static_prio));
+}
+
+/*
+ * Calculate the current priority, i.e. the priority
+ * taken into account by the scheduler. This value might
+ * be boosted by RT tasks, or might be boosted by
+ * interactivity modifiers. Will be RT if the task got
+ * RT-boosted. If not then it returns p->normal_prio.
+ */
+static int effective_prio(struct task_struct *p)
+{
+ p->normal_prio = normal_prio(p);
+ /*
+ * If we are RT tasks or we were boosted to RT priority,
+ * keep the priority unchanged. Otherwise, update priority
+ * to the normal priority:
+ */
+ if (!rt_prio(p->prio))
+ return p->normal_prio;
+ return p->prio;
+}
+
+/**
+ * task_curr - is this task currently executing on a CPU?
+ * @p: the task in question.
+ *
+ * Return: 1 if the task is currently executing. 0 otherwise.
+ */
+inline int task_curr(const struct task_struct *p)
+{
+ return cpu_curr(task_cpu(p)) == p;
+}
+
+/*
+ * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
+ * use the balance_callback list if you want balancing.
+ *
+ * this means any call to check_class_changed() must be followed by a call to
+ * balance_callback().
+ */
+static inline void check_class_changed(struct rq *rq, struct task_struct *p,
+ const struct sched_class *prev_class,
+ int oldprio)
+{
+ if (prev_class != p->sched_class) {
+ if (prev_class->switched_from)
+ prev_class->switched_from(rq, p);
+
+ p->sched_class->switched_to(rq, p);
+ } else if (oldprio != p->prio || dl_task(p))
+ p->sched_class->prio_changed(rq, p, oldprio);
+}
+
+void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
+{
+ if (p->sched_class == rq->curr->sched_class)
+ rq->curr->sched_class->check_preempt_curr(rq, p, flags);
+ else if (p->sched_class > rq->curr->sched_class)
+ resched_curr(rq);
+
+ /*
+ * A queue event has occurred, and we're going to schedule. In
+ * this case, we can save a useless back to back clock update.
+ */
+ if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
+ rq_clock_skip_update(rq);
+}
+
+#ifdef CONFIG_SMP
+
+/*
+ * Per-CPU kthreads are allowed to run on !active && online CPUs, see
+ * __set_cpus_allowed_ptr() and select_fallback_rq().
+ */
+static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
+{
+ if (!cpumask_test_cpu(cpu, p->cpus_ptr))
+ return false;
+
+ if (is_per_cpu_kthread(p))
+ return cpu_online(cpu);
+
+ return cpu_active(cpu);
+}
+
+/*
+ * This is how migration works:
+ *
+ * 1) we invoke migration_cpu_stop() on the target CPU using
+ * stop_one_cpu().
+ * 2) stopper starts to run (implicitly forcing the migrated thread
+ * off the CPU)
+ * 3) it checks whether the migrated task is still in the wrong runqueue.
+ * 4) if it's in the wrong runqueue then the migration thread removes
+ * it and puts it into the right queue.
+ * 5) stopper completes and stop_one_cpu() returns and the migration
+ * is done.
+ */
+
+/*
+ * move_queued_task - move a queued task to new rq.
+ *
+ * Returns (locked) new rq. Old rq's lock is released.
+ */
+static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
+ struct task_struct *p, int new_cpu)
+{
+ lockdep_assert_held(&rq->lock);
+
+ deactivate_task(rq, p, DEQUEUE_NOCLOCK);
+ set_task_cpu(p, new_cpu);
+ rq_unlock(rq, rf);
+
+ rq = cpu_rq(new_cpu);
+
+ rq_lock(rq, rf);
+ BUG_ON(task_cpu(p) != new_cpu);
+ activate_task(rq, p, 0);
+ check_preempt_curr(rq, p, 0);
+
+ return rq;
+}
+
+struct migration_arg {
+ struct task_struct *task;
+ int dest_cpu;
+};
+
+/*
+ * Move (not current) task off this CPU, onto the destination CPU. We're doing
+ * this because either it can't run here any more (set_cpus_allowed()
+ * away from this CPU, or CPU going down), or because we're
+ * attempting to rebalance this task on exec (sched_exec).
+ *
+ * So we race with normal scheduler movements, but that's OK, as long
+ * as the task is no longer on this CPU.
+ */
+static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
+ struct task_struct *p, int dest_cpu)
+{
+ /* Affinity changed (again). */
+ if (!is_cpu_allowed(p, dest_cpu))
+ return rq;
+
+ update_rq_clock(rq);
+ rq = move_queued_task(rq, rf, p, dest_cpu);
+
+ return rq;
+}
+
+/*
+ * migration_cpu_stop - this will be executed by a highprio stopper thread
+ * and performs thread migration by bumping thread off CPU then
+ * 'pushing' onto another runqueue.
+ */
+static int migration_cpu_stop(void *data)
+{
+ struct migration_arg *arg = data;
+ struct task_struct *p = arg->task;
+ struct rq *rq = this_rq();
+ struct rq_flags rf;
+
+ /*
+ * The original target CPU might have gone down and we might
+ * be on another CPU but it doesn't matter.
+ */
+ local_irq_disable();
+ /*
+ * We need to explicitly wake pending tasks before running
+ * __migrate_task() such that we will not miss enforcing cpus_ptr
+ * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
+ */
+ flush_smp_call_function_from_idle();
+
+ raw_spin_lock(&p->pi_lock);
+ rq_lock(rq, &rf);
+ /*
+ * If task_rq(p) != rq, it cannot be migrated here, because we're
+ * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
+ * we're holding p->pi_lock.
+ */
+ if (task_rq(p) == rq) {
+ if (task_on_rq_queued(p))
+ rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
+ else
+ p->wake_cpu = arg->dest_cpu;
+ }
+ rq_unlock(rq, &rf);
+ raw_spin_unlock(&p->pi_lock);
+
+ local_irq_enable();
+ return 0;
+}
+
+/*
+ * sched_class::set_cpus_allowed must do the below, but is not required to
+ * actually call this function.
+ */
+void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
+{
+ cpumask_copy(&p->cpus_mask, new_mask);
+ p->nr_cpus_allowed = cpumask_weight(new_mask);
+}
+
+void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
+{
+ struct rq *rq = task_rq(p);
+ bool queued, running;
+
+ lockdep_assert_held(&p->pi_lock);
+
+ queued = task_on_rq_queued(p);
+ running = task_current(rq, p);
+
+ if (queued) {
+ /*
+ * Because __kthread_bind() calls this on blocked tasks without
+ * holding rq->lock.
+ */
+ lockdep_assert_held(&rq->lock);
+ dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
+ }
+ if (running)
+ put_prev_task(rq, p);
+
+ p->sched_class->set_cpus_allowed(p, new_mask);
+
+ if (queued)
+ enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
+ if (running)
+ set_next_task(rq, p);
+}
+
+/*
+ * Change a given task's CPU affinity. Migrate the thread to a
+ * proper CPU and schedule it away if the CPU it's executing on
+ * is removed from the allowed bitmask.
+ *
+ * NOTE: the caller must have a valid reference to the task, the
+ * task must not exit() & deallocate itself prematurely. The
+ * call is not atomic; no spinlocks may be held.
+ */
+static int __set_cpus_allowed_ptr(struct task_struct *p,
+ const struct cpumask *new_mask, bool check)
+{
+ const struct cpumask *cpu_valid_mask = cpu_active_mask;
+ unsigned int dest_cpu;
+ struct rq_flags rf;
+ struct rq *rq;
+ int ret = 0;
+
+ rq = task_rq_lock(p, &rf);
+ update_rq_clock(rq);
+
+ if (p->flags & PF_KTHREAD) {
+ /*
+ * Kernel threads are allowed on online && !active CPUs
+ */
+ cpu_valid_mask = cpu_online_mask;
+ }
+
+ /*
+ * Must re-check here, to close a race against __kthread_bind(),
+ * sched_setaffinity() is not guaranteed to observe the flag.
+ */
+ if (check && (p->flags & PF_NO_SETAFFINITY)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (cpumask_equal(&p->cpus_mask, new_mask))
+ goto out;
+
+ /*
+ * Picking a ~random cpu helps in cases where we are changing affinity
+ * for groups of tasks (ie. cpuset), so that load balancing is not
+ * immediately required to distribute the tasks within their new mask.
+ */
+ dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, new_mask);
+ if (dest_cpu >= nr_cpu_ids) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ do_set_cpus_allowed(p, new_mask);
+
+ if (p->flags & PF_KTHREAD) {
+ /*
+ * For kernel threads that do indeed end up on online &&
+ * !active we want to ensure they are strict per-CPU threads.
+ */
+ WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) &&
+ !cpumask_intersects(new_mask, cpu_active_mask) &&
+ p->nr_cpus_allowed != 1);
+ }
+
+ /* Can the task run on the task's current CPU? If so, we're done */
+ if (cpumask_test_cpu(task_cpu(p), new_mask))
+ goto out;
+
+ if (task_running(rq, p) || p->state == TASK_WAKING) {
+ struct migration_arg arg = { p, dest_cpu };
+ /* Need help from migration thread: drop lock and wait. */
+ task_rq_unlock(rq, p, &rf);
+ stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
+ return 0;
+ } else if (task_on_rq_queued(p)) {
+ /*
+ * OK, since we're going to drop the lock immediately
+ * afterwards anyway.
+ */
+ rq = move_queued_task(rq, &rf, p, dest_cpu);
+ }
+out:
+ task_rq_unlock(rq, p, &rf);
+
+ return ret;
+}
+
+int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
+{
+ return __set_cpus_allowed_ptr(p, new_mask, false);
+}
+EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
+
+void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
+{
+#ifdef CONFIG_SCHED_DEBUG
+ /*
+ * We should never call set_task_cpu() on a blocked task,
+ * ttwu() will sort out the placement.
+ */
+ WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
+ !p->on_rq);
+
+ /*
+ * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
+ * because schedstat_wait_{start,end} rebase migrating task's wait_start
+ * time relying on p->on_rq.
+ */
+ WARN_ON_ONCE(p->state == TASK_RUNNING &&
+ p->sched_class == &fair_sched_class &&
+ (p->on_rq && !task_on_rq_migrating(p)));
+
+#ifdef CONFIG_LOCKDEP
+ /*
+ * The caller should hold either p->pi_lock or rq->lock, when changing
+ * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
+ *
+ * sched_move_task() holds both and thus holding either pins the cgroup,
+ * see task_group().
+ *
+ * Furthermore, all task_rq users should acquire both locks, see
+ * task_rq_lock().
+ */
+ WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
+ lockdep_is_held(&task_rq(p)->lock)));
+#endif
+ /*
+ * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
+ */
+ WARN_ON_ONCE(!cpu_online(new_cpu));
+#endif
+
+ trace_sched_migrate_task(p, new_cpu);
+
+ if (task_cpu(p) != new_cpu) {
+ if (p->sched_class->migrate_task_rq)
+ p->sched_class->migrate_task_rq(p, new_cpu);
+ p->se.nr_migrations++;
+ rseq_migrate(p);
+ perf_event_task_migrate(p);
+ }
+
+ __set_task_cpu(p, new_cpu);
+}
+
+#ifdef CONFIG_NUMA_BALANCING
+static void __migrate_swap_task(struct task_struct *p, int cpu)
+{
+ if (task_on_rq_queued(p)) {
+ struct rq *src_rq, *dst_rq;
+ struct rq_flags srf, drf;
+
+ src_rq = task_rq(p);
+ dst_rq = cpu_rq(cpu);
+
+ rq_pin_lock(src_rq, &srf);
+ rq_pin_lock(dst_rq, &drf);
+
+ deactivate_task(src_rq, p, 0);
+ set_task_cpu(p, cpu);
+ activate_task(dst_rq, p, 0);
+ check_preempt_curr(dst_rq, p, 0);
+
+ rq_unpin_lock(dst_rq, &drf);
+ rq_unpin_lock(src_rq, &srf);
+
+ } else {
+ /*
+ * Task isn't running anymore; make it appear like we migrated
+ * it before it went to sleep. This means on wakeup we make the
+ * previous CPU our target instead of where it really is.
+ */
+ p->wake_cpu = cpu;
+ }
+}
+
+struct migration_swap_arg {
+ struct task_struct *src_task, *dst_task;
+ int src_cpu, dst_cpu;
+};
+
+static int migrate_swap_stop(void *data)
+{
+ struct migration_swap_arg *arg = data;
+ struct rq *src_rq, *dst_rq;
+ int ret = -EAGAIN;
+
+ if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
+ return -EAGAIN;
+
+ src_rq = cpu_rq(arg->src_cpu);
+ dst_rq = cpu_rq(arg->dst_cpu);
+
+ double_raw_lock(&arg->src_task->pi_lock,
+ &arg->dst_task->pi_lock);
+ double_rq_lock(src_rq, dst_rq);
+
+ if (task_cpu(arg->dst_task) != arg->dst_cpu)
+ goto unlock;
+
+ if (task_cpu(arg->src_task) != arg->src_cpu)
+ goto unlock;
+
+ if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr))
+ goto unlock;
+
+ if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr))
+ goto unlock;
+
+ __migrate_swap_task(arg->src_task, arg->dst_cpu);
+ __migrate_swap_task(arg->dst_task, arg->src_cpu);
+
+ ret = 0;
+
+unlock:
+ double_rq_unlock(src_rq, dst_rq);
+ raw_spin_unlock(&arg->dst_task->pi_lock);
+ raw_spin_unlock(&arg->src_task->pi_lock);
+
+ return ret;
+}
+
+/*
+ * Cross migrate two tasks
+ */
+int migrate_swap(struct task_struct *cur, struct task_struct *p,
+ int target_cpu, int curr_cpu)
+{
+ struct migration_swap_arg arg;
+ int ret = -EINVAL;
+
+ arg = (struct migration_swap_arg){
+ .src_task = cur,
+ .src_cpu = curr_cpu,
+ .dst_task = p,
+ .dst_cpu = target_cpu,
+ };
+
+ if (arg.src_cpu == arg.dst_cpu)
+ goto out;
+
+ /*
+ * These three tests are all lockless; this is OK since all of them
+ * will be re-checked with proper locks held further down the line.
+ */
+ if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
+ goto out;
+
+ if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr))
+ goto out;
+
+ if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr))
+ goto out;
+
+ trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
+ ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
+
+out:
+ return ret;
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
+/*
+ * wait_task_inactive - wait for a thread to unschedule.
+ *
+ * If @match_state is nonzero, it's the @p->state value just checked and
+ * not expected to change. If it changes, i.e. @p might have woken up,
+ * then return zero. When we succeed in waiting for @p to be off its CPU,
+ * we return a positive number (its total switch count). If a second call
+ * a short while later returns the same number, the caller can be sure that
+ * @p has remained unscheduled the whole time.
+ *
+ * The caller must ensure that the task *will* unschedule sometime soon,
+ * else this function might spin for a *long* time. This function can't
+ * be called with interrupts off, or it may introduce deadlock with
+ * smp_call_function() if an IPI is sent by the same process we are
+ * waiting to become inactive.
+ */
+unsigned long wait_task_inactive(struct task_struct *p, long match_state)
+{
+ int running, queued;
+ struct rq_flags rf;
+ unsigned long ncsw;
+ struct rq *rq;
+
+ for (;;) {
+ /*
+ * We do the initial early heuristics without holding
+ * any task-queue locks at all. We'll only try to get
+ * the runqueue lock when things look like they will
+ * work out!
+ */
+ rq = task_rq(p);
+
+ /*
+ * If the task is actively running on another CPU
+ * still, just relax and busy-wait without holding
+ * any locks.
+ *
+ * NOTE! Since we don't hold any locks, it's not
+ * even sure that "rq" stays as the right runqueue!
+ * But we don't care, since "task_running()" will
+ * return false if the runqueue has changed and p
+ * is actually now running somewhere else!
+ */
+ while (task_running(rq, p)) {
+ if (match_state && unlikely(p->state != match_state))
+ return 0;
+ cpu_relax();
+ }
+
+ /*
+ * Ok, time to look more closely! We need the rq
+ * lock now, to be *sure*. If we're wrong, we'll
+ * just go back and repeat.
+ */
+ rq = task_rq_lock(p, &rf);
+ trace_sched_wait_task(p);
+ running = task_running(rq, p);
+ queued = task_on_rq_queued(p);
+ ncsw = 0;
+ if (!match_state || p->state == match_state)
+ ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
+ task_rq_unlock(rq, p, &rf);
+
+ /*
+ * If it changed from the expected state, bail out now.
+ */
+ if (unlikely(!ncsw))
+ break;
+
+ /*
+ * Was it really running after all now that we
+ * checked with the proper locks actually held?
+ *
+ * Oops. Go back and try again..
+ */
+ if (unlikely(running)) {
+ cpu_relax();
+ continue;
+ }
+
+ /*
+ * It's not enough that it's not actively running,
+ * it must be off the runqueue _entirely_, and not
+ * preempted!
+ *
+ * So if it was still runnable (but just not actively
+ * running right now), it's preempted, and we should
+ * yield - it could be a while.
+ */
+ if (unlikely(queued)) {
+ ktime_t to = NSEC_PER_SEC / HZ;
+
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ schedule_hrtimeout(&to, HRTIMER_MODE_REL);
+ continue;
+ }
+
+ /*
+ * Ahh, all good. It wasn't running, and it wasn't
+ * runnable, which means that it will never become
+ * running in the future either. We're all done!
+ */
+ break;
+ }
+
+ return ncsw;
+}
+
+/***
+ * kick_process - kick a running thread to enter/exit the kernel
+ * @p: the to-be-kicked thread
+ *
+ * Cause a process which is running on another CPU to enter
+ * kernel-mode, without any delay. (to get signals handled.)
+ *
+ * NOTE: this function doesn't have to take the runqueue lock,
+ * because all it wants to ensure is that the remote task enters
+ * the kernel. If the IPI races and the task has been migrated
+ * to another CPU then no harm is done and the purpose has been
+ * achieved as well.
+ */
+void kick_process(struct task_struct *p)
+{
+ int cpu;
+
+ preempt_disable();
+ cpu = task_cpu(p);
+ if ((cpu != smp_processor_id()) && task_curr(p))
+ smp_send_reschedule(cpu);
+ preempt_enable();
+}
+EXPORT_SYMBOL_GPL(kick_process);
+
+/*
+ * ->cpus_ptr is protected by both rq->lock and p->pi_lock
+ *
+ * A few notes on cpu_active vs cpu_online:
+ *
+ * - cpu_active must be a subset of cpu_online
+ *
+ * - 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.
+ *
+ * - on CPU-down we clear cpu_active() to mask the sched domains and
+ * avoid the load balancer to place new tasks on the to be removed
+ * CPU. Existing tasks will remain running there and will be taken
+ * off.
+ *
+ * This means that fallback selection must not select !active CPUs.
+ * And can assume that any active CPU must be online. Conversely
+ * select_task_rq() below may allow selection of !active CPUs in order
+ * to satisfy the above rules.
+ */
+static int select_fallback_rq(int cpu, struct task_struct *p)
+{
+ int nid = cpu_to_node(cpu);
+ const struct cpumask *nodemask = NULL;
+ enum { cpuset, possible, fail } state = cpuset;
+ int dest_cpu;
+
+ /*
+ * If the node that the CPU is on has been offlined, cpu_to_node()
+ * will return -1. There is no CPU on the node, and we should
+ * select the CPU on the other node.
+ */
+ if (nid != -1) {
+ nodemask = cpumask_of_node(nid);
+
+ /* Look for allowed, online CPU in same node. */
+ for_each_cpu(dest_cpu, nodemask) {
+ if (!cpu_active(dest_cpu))
+ continue;
+ if (cpumask_test_cpu(dest_cpu, p->cpus_ptr))
+ return dest_cpu;
+ }
+ }
+
+ for (;;) {
+ /* Any allowed, online CPU? */
+ for_each_cpu(dest_cpu, p->cpus_ptr) {
+ if (!is_cpu_allowed(p, dest_cpu))
+ continue;
+
+ goto out;
+ }
+
+ /* No more Mr. Nice Guy. */
+ switch (state) {
+ case cpuset:
+ if (IS_ENABLED(CONFIG_CPUSETS)) {
+ cpuset_cpus_allowed_fallback(p);
+ state = possible;
+ break;
+ }
+ fallthrough;
+ case possible:
+ do_set_cpus_allowed(p, cpu_possible_mask);
+ state = fail;
+ break;
+
+ case fail:
+ BUG();
+ break;
+ }
+ }
+
+out:
+ if (state != cpuset) {
+ /*
+ * Don't tell them about moving exiting tasks or
+ * kernel threads (both mm NULL), since they never
+ * leave kernel.
+ */
+ if (p->mm && printk_ratelimit()) {
+ printk_deferred("process %d (%s) no longer affine to cpu%d\n",
+ task_pid_nr(p), p->comm, cpu);
+ }
+ }
+
+ return dest_cpu;
+}
+
+/*
+ * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
+ */
+static inline
+int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
+{
+ lockdep_assert_held(&p->pi_lock);
+
+ if (p->nr_cpus_allowed > 1)
+ cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
+ else
+ cpu = cpumask_any(p->cpus_ptr);
+
+ /*
+ * In order not to call set_task_cpu() on a blocking task we need
+ * to rely on ttwu() to place the task on a valid ->cpus_ptr
+ * CPU.
+ *
+ * Since this is common to all placement strategies, this lives here.
+ *
+ * [ this allows ->select_task() to simply return task_cpu(p) and
+ * not worry about this generic constraint ]
+ */
+ if (unlikely(!is_cpu_allowed(p, cpu)))
+ cpu = select_fallback_rq(task_cpu(p), p);
+
+ return cpu;
+}
+
+void sched_set_stop_task(int cpu, struct task_struct *stop)
+{
+ struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
+ struct task_struct *old_stop = cpu_rq(cpu)->stop;
+
+ if (stop) {
+ /*
+ * Make it appear like a SCHED_FIFO task, its something
+ * userspace knows about and won't get confused about.
+ *
+ * Also, it will make PI more or less work without too
+ * much confusion -- but then, stop work should not
+ * rely on PI working anyway.
+ */
+ sched_setscheduler_nocheck(stop, SCHED_FIFO, &param);
+
+ stop->sched_class = &stop_sched_class;
+ }
+
+ cpu_rq(cpu)->stop = stop;
+
+ if (old_stop) {
+ /*
+ * Reset it back to a normal scheduling class so that
+ * it can die in pieces.
+ */
+ old_stop->sched_class = &rt_sched_class;
+ }
+}
+
+#else
+
+static inline int __set_cpus_allowed_ptr(struct task_struct *p,
+ const struct cpumask *new_mask, bool check)
+{
+ return set_cpus_allowed_ptr(p, new_mask);
+}
+
+#endif /* CONFIG_SMP */
+
+static void
+ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
+{
+ struct rq *rq;
+
+ if (!schedstat_enabled())
+ return;
+
+ rq = this_rq();
+
+#ifdef CONFIG_SMP
+ if (cpu == rq->cpu) {
+ __schedstat_inc(rq->ttwu_local);
+ __schedstat_inc(p->se.statistics.nr_wakeups_local);
+ } else {
+ struct sched_domain *sd;
+
+ __schedstat_inc(p->se.statistics.nr_wakeups_remote);
+ rcu_read_lock();
+ for_each_domain(rq->cpu, sd) {
+ if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
+ __schedstat_inc(sd->ttwu_wake_remote);
+ break;
+ }
+ }
+ rcu_read_unlock();
+ }
+
+ if (wake_flags & WF_MIGRATED)
+ __schedstat_inc(p->se.statistics.nr_wakeups_migrate);
+#endif /* CONFIG_SMP */
+
+ __schedstat_inc(rq->ttwu_count);
+ __schedstat_inc(p->se.statistics.nr_wakeups);
+
+ if (wake_flags & WF_SYNC)
+ __schedstat_inc(p->se.statistics.nr_wakeups_sync);
+}
+
+/*
+ * Mark the task runnable and perform wakeup-preemption.
+ */
+static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
+ struct rq_flags *rf)
+{
+ check_preempt_curr(rq, p, wake_flags);
+ p->state = TASK_RUNNING;
+ trace_sched_wakeup(p);
+
+#ifdef CONFIG_SMP
+ if (p->sched_class->task_woken) {
+ /*
+ * Our task @p is fully woken up and running; so its safe to
+ * drop the rq->lock, hereafter rq is only used for statistics.
+ */
+ rq_unpin_lock(rq, rf);
+ p->sched_class->task_woken(rq, p);
+ rq_repin_lock(rq, rf);
+ }
+
+ if (rq->idle_stamp) {
+ u64 delta = rq_clock(rq) - rq->idle_stamp;
+ u64 max = 2*rq->max_idle_balance_cost;
+
+ update_avg(&rq->avg_idle, delta);
+
+ if (rq->avg_idle > max)
+ rq->avg_idle = max;
+
+ rq->idle_stamp = 0;
+ }
+#endif
+}
+
+static void
+ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
+ struct rq_flags *rf)
+{
+ int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
+
+ lockdep_assert_held(&rq->lock);
+
+ if (p->sched_contributes_to_load)
+ rq->nr_uninterruptible--;
+
+#ifdef CONFIG_SMP
+ if (wake_flags & WF_MIGRATED)
+ en_flags |= ENQUEUE_MIGRATED;
+ else
+#endif
+ if (p->in_iowait) {
+ delayacct_blkio_end(p);
+ atomic_dec(&task_rq(p)->nr_iowait);
+ }
+
+ activate_task(rq, p, en_flags);
+ ttwu_do_wakeup(rq, p, wake_flags, rf);
+}
+
+/*
+ * Consider @p being inside a wait loop:
+ *
+ * for (;;) {
+ * set_current_state(TASK_UNINTERRUPTIBLE);
+ *
+ * if (CONDITION)
+ * break;
+ *
+ * schedule();
+ * }
+ * __set_current_state(TASK_RUNNING);
+ *
+ * between set_current_state() and schedule(). In this case @p is still
+ * runnable, so all that needs doing is change p->state back to TASK_RUNNING in
+ * an atomic manner.
+ *
+ * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq
+ * then schedule() must still happen and p->state can be changed to
+ * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we
+ * need to do a full wakeup with enqueue.
+ *
+ * Returns: %true when the wakeup is done,
+ * %false otherwise.
+ */
+static int ttwu_runnable(struct task_struct *p, int wake_flags)
+{
+ struct rq_flags rf;
+ struct rq *rq;
+ int ret = 0;
+
+ rq = __task_rq_lock(p, &rf);
+ if (task_on_rq_queued(p)) {
+ /* check_preempt_curr() may use rq clock */
+ update_rq_clock(rq);
+ ttwu_do_wakeup(rq, p, wake_flags, &rf);
+ ret = 1;
+ }
+ __task_rq_unlock(rq, &rf);
+
+ return ret;
+}
+
+#ifdef CONFIG_SMP
+void sched_ttwu_pending(void *arg)
+{
+ struct llist_node *llist = arg;
+ struct rq *rq = this_rq();
+ struct task_struct *p, *t;
+ struct rq_flags rf;
+
+ if (!llist)
+ return;
+
+ /*
+ * rq::ttwu_pending racy indication of out-standing wakeups.
+ * Races such that false-negatives are possible, since they
+ * are shorter lived that false-positives would be.
+ */
+ WRITE_ONCE(rq->ttwu_pending, 0);
+
+ rq_lock_irqsave(rq, &rf);
+ update_rq_clock(rq);
+
+ llist_for_each_entry_safe(p, t, llist, wake_entry.llist) {
+ if (WARN_ON_ONCE(p->on_cpu))
+ smp_cond_load_acquire(&p->on_cpu, !VAL);
+
+ if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq)))
+ set_task_cpu(p, cpu_of(rq));
+
+ ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
+ }
+
+ rq_unlock_irqrestore(rq, &rf);
+}
+
+void send_call_function_single_ipi(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ if (!set_nr_if_polling(rq->idle))
+ arch_send_call_function_single_ipi(cpu);
+ else
+ trace_sched_wake_idle_without_ipi(cpu);
+}
+
+/*
+ * Queue a task on the target CPUs wake_list and wake the CPU via IPI if
+ * necessary. The wakee CPU on receipt of the IPI will queue the task
+ * via sched_ttwu_wakeup() for activation so the wakee incurs the cost
+ * of the wakeup instead of the waker.
+ */
+static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
+
+ WRITE_ONCE(rq->ttwu_pending, 1);
+ __smp_call_single_queue(cpu, &p->wake_entry.llist);
+}
+
+void wake_up_if_idle(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ struct rq_flags rf;
+
+ rcu_read_lock();
+
+ if (!is_idle_task(rcu_dereference(rq->curr)))
+ goto out;
+
+ if (set_nr_if_polling(rq->idle)) {
+ trace_sched_wake_idle_without_ipi(cpu);
+ } else {
+ rq_lock_irqsave(rq, &rf);
+ if (is_idle_task(rq->curr))
+ smp_send_reschedule(cpu);
+ /* Else CPU is not idle, do nothing here: */
+ rq_unlock_irqrestore(rq, &rf);
+ }
+
+out:
+ rcu_read_unlock();
+}
+
+bool cpus_share_cache(int this_cpu, int that_cpu)
+{
+ if (this_cpu == that_cpu)
+ return true;
+
+ return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
+}
+
+static inline bool ttwu_queue_cond(int cpu, int wake_flags)
+{
+ /*
+ * If the CPU does not share cache, then queue the task on the
+ * remote rqs wakelist to avoid accessing remote data.
+ */
+ if (!cpus_share_cache(smp_processor_id(), cpu))
+ return true;
+
+ /*
+ * If the task is descheduling and the only running task on the
+ * CPU then use the wakelist to offload the task activation to
+ * the soon-to-be-idle CPU as the current CPU is likely busy.
+ * nr_running is checked to avoid unnecessary task stacking.
+ *
+ * Note that we can only get here with (wakee) p->on_rq=0,
+ * p->on_cpu can be whatever, we've done the dequeue, so
+ * the wakee has been accounted out of ->nr_running.
+ */
+ if ((wake_flags & WF_ON_CPU) && !cpu_rq(cpu)->nr_running)
+ return true;
+
+ return false;
+}
+
+static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
+{
+ if (sched_feat(TTWU_QUEUE) && ttwu_queue_cond(cpu, wake_flags)) {
+ if (WARN_ON_ONCE(cpu == smp_processor_id()))
+ return false;
+
+ sched_clock_cpu(cpu); /* Sync clocks across CPUs */
+ __ttwu_queue_wakelist(p, cpu, wake_flags);
+ return true;
+ }
+
+ return false;
+}
+
+#else /* !CONFIG_SMP */
+
+static inline bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
+{
+ return false;
+}
+
+#endif /* CONFIG_SMP */
+
+static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
+{
+ struct rq *rq = cpu_rq(cpu);
+ struct rq_flags rf;
+
+ if (ttwu_queue_wakelist(p, cpu, wake_flags))
+ return;
+
+ rq_lock(rq, &rf);
+ update_rq_clock(rq);
+ ttwu_do_activate(rq, p, wake_flags, &rf);
+ rq_unlock(rq, &rf);
+}
+
+/*
+ * Notes on Program-Order guarantees on SMP systems.
+ *
+ * MIGRATION
+ *
+ * The basic program-order guarantee on SMP systems is that when a task [t]
+ * migrates, all its activity on its old CPU [c0] happens-before any subsequent
+ * execution on its new CPU [c1].
+ *
+ * For migration (of runnable tasks) this is provided by the following means:
+ *
+ * A) UNLOCK of the rq(c0)->lock scheduling out task t
+ * B) migration for t is required to synchronize *both* rq(c0)->lock and
+ * rq(c1)->lock (if not at the same time, then in that order).
+ * C) LOCK of the rq(c1)->lock scheduling in task
+ *
+ * Release/acquire chaining guarantees that B happens after A and C after B.
+ * Note: the CPU doing B need not be c0 or c1
+ *
+ * Example:
+ *
+ * CPU0 CPU1 CPU2
+ *
+ * LOCK rq(0)->lock
+ * sched-out X
+ * sched-in Y
+ * UNLOCK rq(0)->lock
+ *
+ * LOCK rq(0)->lock // orders against CPU0
+ * dequeue X
+ * UNLOCK rq(0)->lock
+ *
+ * LOCK rq(1)->lock
+ * enqueue X
+ * UNLOCK rq(1)->lock
+ *
+ * LOCK rq(1)->lock // orders against CPU2
+ * sched-out Z
+ * sched-in X
+ * UNLOCK rq(1)->lock
+ *
+ *
+ * BLOCKING -- aka. SLEEP + WAKEUP
+ *
+ * For blocking we (obviously) need to provide the same guarantee as for
+ * migration. However the means are completely different as there is no lock
+ * chain to provide order. Instead we do:
+ *
+ * 1) smp_store_release(X->on_cpu, 0) -- finish_task()
+ * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up()
+ *
+ * Example:
+ *
+ * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
+ *
+ * LOCK rq(0)->lock LOCK X->pi_lock
+ * dequeue X
+ * sched-out X
+ * smp_store_release(X->on_cpu, 0);
+ *
+ * smp_cond_load_acquire(&X->on_cpu, !VAL);
+ * X->state = WAKING
+ * set_task_cpu(X,2)
+ *
+ * LOCK rq(2)->lock
+ * enqueue X
+ * X->state = RUNNING
+ * UNLOCK rq(2)->lock
+ *
+ * LOCK rq(2)->lock // orders against CPU1
+ * sched-out Z
+ * sched-in X
+ * UNLOCK rq(2)->lock
+ *
+ * UNLOCK X->pi_lock
+ * UNLOCK rq(0)->lock
+ *
+ *
+ * However, for wakeups there is a second guarantee we must provide, namely we
+ * must ensure that CONDITION=1 done by the caller can not be reordered with
+ * accesses to the task state; see try_to_wake_up() and set_current_state().
+ */
+
+/**
+ * try_to_wake_up - wake up a thread
+ * @p: the thread to be awakened
+ * @state: the mask of task states that can be woken
+ * @wake_flags: wake modifier flags (WF_*)
+ *
+ * Conceptually does:
+ *
+ * If (@state & @p->state) @p->state = TASK_RUNNING.
+ *
+ * If the task was not queued/runnable, also place it back on a runqueue.
+ *
+ * This function is atomic against schedule() which would dequeue the task.
+ *
+ * It issues a full memory barrier before accessing @p->state, see the comment
+ * with set_current_state().
+ *
+ * Uses p->pi_lock to serialize against concurrent wake-ups.
+ *
+ * Relies on p->pi_lock stabilizing:
+ * - p->sched_class
+ * - p->cpus_ptr
+ * - p->sched_task_group
+ * in order to do migration, see its use of select_task_rq()/set_task_cpu().
+ *
+ * Tries really hard to only take one task_rq(p)->lock for performance.
+ * Takes rq->lock in:
+ * - ttwu_runnable() -- old rq, unavoidable, see comment there;
+ * - ttwu_queue() -- new rq, for enqueue of the task;
+ * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us.
+ *
+ * As a consequence we race really badly with just about everything. See the
+ * many memory barriers and their comments for details.
+ *
+ * Return: %true if @p->state changes (an actual wakeup was done),
+ * %false otherwise.
+ */
+static int
+try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
+{
+ unsigned long flags;
+ int cpu, success = 0;
+
+ preempt_disable();
+ if (p == current) {
+ /*
+ * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
+ * == smp_processor_id()'. Together this means we can special
+ * case the whole 'p->on_rq && ttwu_runnable()' case below
+ * without taking any locks.
+ *
+ * In particular:
+ * - we rely on Program-Order guarantees for all the ordering,
+ * - we're serialized against set_special_state() by virtue of
+ * it disabling IRQs (this allows not taking ->pi_lock).
+ */
+ if (!(p->state & state))
+ goto out;
+
+ success = 1;
+ trace_sched_waking(p);
+ p->state = TASK_RUNNING;
+ trace_sched_wakeup(p);
+ goto out;
+ }
+
+ /*
+ * If we are going to wake up a thread waiting for CONDITION we
+ * need to ensure that CONDITION=1 done by the caller can not be
+ * reordered with p->state check below. This pairs with smp_store_mb()
+ * in set_current_state() that the waiting thread does.
+ */
+ raw_spin_lock_irqsave(&p->pi_lock, flags);
+ smp_mb__after_spinlock();
+ if (!(p->state & state))
+ goto unlock;
+
+ trace_sched_waking(p);
+
+ /* We're going to change ->state: */
+ success = 1;
+
+ /*
+ * Ensure we load p->on_rq _after_ p->state, otherwise it would
+ * be possible to, falsely, observe p->on_rq == 0 and get stuck
+ * in smp_cond_load_acquire() below.
+ *
+ * sched_ttwu_pending() try_to_wake_up()
+ * STORE p->on_rq = 1 LOAD p->state
+ * UNLOCK rq->lock
+ *
+ * __schedule() (switch to task 'p')
+ * LOCK rq->lock smp_rmb();
+ * smp_mb__after_spinlock();
+ * UNLOCK rq->lock
+ *
+ * [task p]
+ * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq
+ *
+ * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
+ * __schedule(). See the comment for smp_mb__after_spinlock().
+ *
+ * A similar smb_rmb() lives in try_invoke_on_locked_down_task().
+ */
+ smp_rmb();
+ if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
+ goto unlock;
+
+#ifdef CONFIG_SMP
+ /*
+ * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
+ * possible to, falsely, observe p->on_cpu == 0.
+ *
+ * One must be running (->on_cpu == 1) in order to remove oneself
+ * from the runqueue.
+ *
+ * __schedule() (switch to task 'p') try_to_wake_up()
+ * STORE p->on_cpu = 1 LOAD p->on_rq
+ * UNLOCK rq->lock
+ *
+ * __schedule() (put 'p' to sleep)
+ * LOCK rq->lock smp_rmb();
+ * smp_mb__after_spinlock();
+ * STORE p->on_rq = 0 LOAD p->on_cpu
+ *
+ * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
+ * __schedule(). See the comment for smp_mb__after_spinlock().
+ *
+ * Form a control-dep-acquire with p->on_rq == 0 above, to ensure
+ * schedule()'s deactivate_task() has 'happened' and p will no longer
+ * care about it's own p->state. See the comment in __schedule().
+ */
+ smp_acquire__after_ctrl_dep();
+
+ /*
+ * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq
+ * == 0), which means we need to do an enqueue, change p->state to
+ * TASK_WAKING such that we can unlock p->pi_lock before doing the
+ * enqueue, such as ttwu_queue_wakelist().
+ */
+ p->state = TASK_WAKING;
+
+ /*
+ * If the owning (remote) CPU is still in the middle of schedule() with
+ * this task as prev, considering queueing p on the remote CPUs wake_list
+ * which potentially sends an IPI instead of spinning on p->on_cpu to
+ * let the waker make forward progress. This is safe because IRQs are
+ * disabled and the IPI will deliver after on_cpu is cleared.
+ *
+ * Ensure we load task_cpu(p) after p->on_cpu:
+ *
+ * set_task_cpu(p, cpu);
+ * STORE p->cpu = @cpu
+ * __schedule() (switch to task 'p')
+ * LOCK rq->lock
+ * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu)
+ * STORE p->on_cpu = 1 LOAD p->cpu
+ *
+ * to ensure we observe the correct CPU on which the task is currently
+ * scheduling.
+ */
+ if (smp_load_acquire(&p->on_cpu) &&
+ ttwu_queue_wakelist(p, task_cpu(p), wake_flags | WF_ON_CPU))
+ goto unlock;
+
+ /*
+ * If the owning (remote) CPU is still in the middle of schedule() with
+ * this task as prev, wait until its done referencing the task.
+ *
+ * Pairs with the smp_store_release() in finish_task().
+ *
+ * This ensures that tasks getting woken will be fully ordered against
+ * their previous state and preserve Program Order.
+ */
+ smp_cond_load_acquire(&p->on_cpu, !VAL);
+
+ cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
+ if (task_cpu(p) != cpu) {
+ if (p->in_iowait) {
+ delayacct_blkio_end(p);
+ atomic_dec(&task_rq(p)->nr_iowait);
+ }
+
+ wake_flags |= WF_MIGRATED;
+ psi_ttwu_dequeue(p);
+ set_task_cpu(p, cpu);
+ }
+#else
+ cpu = task_cpu(p);
+#endif /* CONFIG_SMP */
+
+ ttwu_queue(p, cpu, wake_flags);
+unlock:
+ raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+out:
+ if (success)
+ ttwu_stat(p, task_cpu(p), wake_flags);
+ preempt_enable();
+
+ return success;
+}
+
+/**
+ * try_invoke_on_locked_down_task - Invoke a function on task in fixed state
+ * @p: Process for which the function is to be invoked, can be @current.
+ * @func: Function to invoke.
+ * @arg: Argument to function.
+ *
+ * If the specified task can be quickly locked into a definite state
+ * (either sleeping or on a given runqueue), arrange to keep it in that
+ * state while invoking @func(@arg). This function can use ->on_rq and
+ * task_curr() to work out what the state is, if required. Given that
+ * @func can be invoked with a runqueue lock held, it had better be quite
+ * lightweight.
+ *
+ * Returns:
+ * @false if the task slipped out from under the locks.
+ * @true if the task was locked onto a runqueue or is sleeping.
+ * However, @func can override this by returning @false.
+ */
+bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct task_struct *t, void *arg), void *arg)
+{
+ struct rq_flags rf;
+ bool ret = false;
+ struct rq *rq;
+
+ raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
+ if (p->on_rq) {
+ rq = __task_rq_lock(p, &rf);
+ if (task_rq(p) == rq)
+ ret = func(p, arg);
+ rq_unlock(rq, &rf);
+ } else {
+ switch (p->state) {
+ case TASK_RUNNING:
+ case TASK_WAKING:
+ break;
+ default:
+ smp_rmb(); // See smp_rmb() comment in try_to_wake_up().
+ if (!p->on_rq)
+ ret = func(p, arg);
+ }
+ }
+ raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
+ return ret;
+}
+
+/**
+ * wake_up_process - Wake up a specific process
+ * @p: The process to be woken up.
+ *
+ * Attempt to wake up the nominated process and move it to the set of runnable
+ * processes.
+ *
+ * Return: 1 if the process was woken up, 0 if it was already running.
+ *
+ * This function executes a full memory barrier before accessing the task state.
+ */
+int wake_up_process(struct task_struct *p)
+{
+ return try_to_wake_up(p, TASK_NORMAL, 0);
+}
+EXPORT_SYMBOL(wake_up_process);
+
+int wake_up_state(struct task_struct *p, unsigned int state)
+{
+ return try_to_wake_up(p, state, 0);
+}
+
+/*
+ * Perform scheduler related setup for a newly forked process p.
+ * p is forked by current.
+ *
+ * __sched_fork() is basic setup used by init_idle() too:
+ */
+static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
+{
+ p->on_rq = 0;
+
+ p->se.on_rq = 0;
+ p->se.exec_start = 0;
+ p->se.sum_exec_runtime = 0;
+ p->se.prev_sum_exec_runtime = 0;
+ p->se.nr_migrations = 0;
+ p->se.vruntime = 0;
+ INIT_LIST_HEAD(&p->se.group_node);
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ p->se.cfs_rq = NULL;
+#endif
+
+#ifdef CONFIG_SCHEDSTATS
+ /* Even if schedstat is disabled, there should not be garbage */
+ memset(&p->se.statistics, 0, sizeof(p->se.statistics));
+#endif
+
+ RB_CLEAR_NODE(&p->dl.rb_node);
+ init_dl_task_timer(&p->dl);
+ init_dl_inactive_task_timer(&p->dl);
+ __dl_clear_params(p);
+
+ INIT_LIST_HEAD(&p->rt.run_list);
+ p->rt.timeout = 0;
+ p->rt.time_slice = sched_rr_timeslice;
+ p->rt.on_rq = 0;
+ p->rt.on_list = 0;
+
+#ifdef CONFIG_PREEMPT_NOTIFIERS
+ INIT_HLIST_HEAD(&p->preempt_notifiers);
+#endif
+
+#ifdef CONFIG_COMPACTION
+ p->capture_control = NULL;
+#endif
+ init_numa_balancing(clone_flags, p);
+#ifdef CONFIG_SMP
+ p->wake_entry.u_flags = CSD_TYPE_TTWU;
+#endif
+}
+
+DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
+
+#ifdef CONFIG_NUMA_BALANCING
+
+void set_numabalancing_state(bool enabled)
+{
+ if (enabled)
+ static_branch_enable(&sched_numa_balancing);
+ else
+ static_branch_disable(&sched_numa_balancing);
+}
+
+#ifdef CONFIG_PROC_SYSCTL
+int sysctl_numa_balancing(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct ctl_table t;
+ int err;
+ int state = static_branch_likely(&sched_numa_balancing);
+
+ if (write && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ t = *table;
+ t.data = &state;
+ err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
+ if (err < 0)
+ return err;
+ if (write)
+ set_numabalancing_state(state);
+ return err;
+}
+#endif
+#endif
+
+#ifdef CONFIG_SCHEDSTATS
+
+DEFINE_STATIC_KEY_FALSE(sched_schedstats);
+static bool __initdata __sched_schedstats = false;
+
+static void set_schedstats(bool enabled)
+{
+ if (enabled)
+ static_branch_enable(&sched_schedstats);
+ else
+ static_branch_disable(&sched_schedstats);
+}
+
+void force_schedstat_enabled(void)
+{
+ if (!schedstat_enabled()) {
+ pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
+ static_branch_enable(&sched_schedstats);
+ }
+}
+
+static int __init setup_schedstats(char *str)
+{
+ int ret = 0;
+ if (!str)
+ goto out;
+
+ /*
+ * This code is called before jump labels have been set up, so we can't
+ * change the static branch directly just yet. Instead set a temporary
+ * variable so init_schedstats() can do it later.
+ */
+ if (!strcmp(str, "enable")) {
+ __sched_schedstats = true;
+ ret = 1;
+ } else if (!strcmp(str, "disable")) {
+ __sched_schedstats = false;
+ ret = 1;
+ }
+out:
+ if (!ret)
+ pr_warn("Unable to parse schedstats=\n");
+
+ return ret;
+}
+__setup("schedstats=", setup_schedstats);
+
+static void __init init_schedstats(void)
+{
+ set_schedstats(__sched_schedstats);
+}
+
+#ifdef CONFIG_PROC_SYSCTL
+int sysctl_schedstats(struct ctl_table *table, int write, void *buffer,
+ size_t *lenp, loff_t *ppos)
+{
+ struct ctl_table t;
+ int err;
+ int state = static_branch_likely(&sched_schedstats);
+
+ if (write && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ t = *table;
+ t.data = &state;
+ err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
+ if (err < 0)
+ return err;
+ if (write)
+ set_schedstats(state);
+ return err;
+}
+#endif /* CONFIG_PROC_SYSCTL */
+#else /* !CONFIG_SCHEDSTATS */
+static inline void init_schedstats(void) {}
+#endif /* CONFIG_SCHEDSTATS */
+
+/*
+ * fork()/clone()-time setup:
+ */
+int sched_fork(unsigned long clone_flags, struct task_struct *p)
+{
+ __sched_fork(clone_flags, p);
+ /*
+ * We mark the process as NEW here. This guarantees that
+ * nobody will actually run it, and a signal or other external
+ * event cannot wake it up and insert it on the runqueue either.
+ */
+ p->state = TASK_NEW;
+
+ /*
+ * Make sure we do not leak PI boosting priority to the child.
+ */
+ p->prio = current->normal_prio;
+
+ uclamp_fork(p);
+
+ /*
+ * Revert to default priority/policy on fork if requested.
+ */
+ if (unlikely(p->sched_reset_on_fork)) {
+ if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
+ p->policy = SCHED_NORMAL;
+ p->static_prio = NICE_TO_PRIO(0);
+ p->rt_priority = 0;
+ } else if (PRIO_TO_NICE(p->static_prio) < 0)
+ p->static_prio = NICE_TO_PRIO(0);
+
+ p->prio = p->normal_prio = p->static_prio;
+ set_load_weight(p);
+
+ /*
+ * We don't need the reset flag anymore after the fork. It has
+ * fulfilled its duty:
+ */
+ p->sched_reset_on_fork = 0;
+ }
+
+ if (dl_prio(p->prio))
+ return -EAGAIN;
+ else if (rt_prio(p->prio))
+ p->sched_class = &rt_sched_class;
+ else
+ p->sched_class = &fair_sched_class;
+
+ init_entity_runnable_average(&p->se);
+
+#ifdef CONFIG_SCHED_INFO
+ if (likely(sched_info_on()))
+ memset(&p->sched_info, 0, sizeof(p->sched_info));
+#endif
+#if defined(CONFIG_SMP)
+ p->on_cpu = 0;
+#endif
+ init_task_preempt_count(p);
+#ifdef CONFIG_SMP
+ plist_node_init(&p->pushable_tasks, MAX_PRIO);
+ RB_CLEAR_NODE(&p->pushable_dl_tasks);
+#endif
+ return 0;
+}
+
+void sched_post_fork(struct task_struct *p, struct kernel_clone_args *kargs)
+{
+ unsigned long flags;
+#ifdef CONFIG_CGROUP_SCHED
+ struct task_group *tg;
+#endif
+
+ raw_spin_lock_irqsave(&p->pi_lock, flags);
+#ifdef CONFIG_CGROUP_SCHED
+ tg = container_of(kargs->cset->subsys[cpu_cgrp_id],
+ struct task_group, css);
+ p->sched_task_group = autogroup_task_group(p, tg);
+#endif
+ rseq_migrate(p);
+ /*
+ * We're setting the CPU for the first time, we don't migrate,
+ * so use __set_task_cpu().
+ */
+ __set_task_cpu(p, smp_processor_id());
+ if (p->sched_class->task_fork)
+ p->sched_class->task_fork(p);
+ raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+
+ uclamp_post_fork(p);
+}
+
+unsigned long to_ratio(u64 period, u64 runtime)
+{
+ if (runtime == RUNTIME_INF)
+ return BW_UNIT;
+
+ /*
+ * Doing this here saves a lot of checks in all
+ * the calling paths, and returning zero seems
+ * safe for them anyway.
+ */
+ if (period == 0)
+ return 0;
+
+ return div64_u64(runtime << BW_SHIFT, period);
+}
+
+/*
+ * wake_up_new_task - wake up a newly created task for the first time.
+ *
+ * This function will do some initial scheduler statistics housekeeping
+ * that must be done for every newly created context, then puts the task
+ * on the runqueue and wakes it.
+ */
+void wake_up_new_task(struct task_struct *p)
+{
+ struct rq_flags rf;
+ struct rq *rq;
+
+ raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
+ p->state = TASK_RUNNING;
+#ifdef CONFIG_SMP
+ /*
+ * Fork balancing, do it here and not earlier because:
+ * - cpus_ptr can change in the fork path
+ * - any previously selected CPU might disappear through hotplug
+ *
+ * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
+ * as we're not fully set-up yet.
+ */
+ p->recent_used_cpu = task_cpu(p);
+ rseq_migrate(p);
+ __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
+#endif
+ rq = __task_rq_lock(p, &rf);
+ update_rq_clock(rq);
+ post_init_entity_util_avg(p);
+
+ activate_task(rq, p, ENQUEUE_NOCLOCK);
+ trace_sched_wakeup_new(p);
+ check_preempt_curr(rq, p, WF_FORK);
+#ifdef CONFIG_SMP
+ if (p->sched_class->task_woken) {
+ /*
+ * Nothing relies on rq->lock after this, so its fine to
+ * drop it.
+ */
+ rq_unpin_lock(rq, &rf);
+ p->sched_class->task_woken(rq, p);
+ rq_repin_lock(rq, &rf);
+ }
+#endif
+ task_rq_unlock(rq, p, &rf);
+}
+
+#ifdef CONFIG_PREEMPT_NOTIFIERS
+
+static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
+
+void preempt_notifier_inc(void)
+{
+ static_branch_inc(&preempt_notifier_key);
+}
+EXPORT_SYMBOL_GPL(preempt_notifier_inc);
+
+void preempt_notifier_dec(void)
+{
+ static_branch_dec(&preempt_notifier_key);
+}
+EXPORT_SYMBOL_GPL(preempt_notifier_dec);
+
+/**
+ * preempt_notifier_register - tell me when current is being preempted & rescheduled
+ * @notifier: notifier struct to register
+ */
+void preempt_notifier_register(struct preempt_notifier *notifier)
+{
+ if (!static_branch_unlikely(&preempt_notifier_key))
+ WARN(1, "registering preempt_notifier while notifiers disabled\n");
+
+ hlist_add_head(&notifier->link, &current->preempt_notifiers);
+}
+EXPORT_SYMBOL_GPL(preempt_notifier_register);
+
+/**
+ * preempt_notifier_unregister - no longer interested in preemption notifications
+ * @notifier: notifier struct to unregister
+ *
+ * This is *not* safe to call from within a preemption notifier.
+ */
+void preempt_notifier_unregister(struct preempt_notifier *notifier)
+{
+ hlist_del(&notifier->link);
+}
+EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
+
+static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
+{
+ struct preempt_notifier *notifier;
+
+ hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
+ notifier->ops->sched_in(notifier, raw_smp_processor_id());
+}
+
+static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
+{
+ if (static_branch_unlikely(&preempt_notifier_key))
+ __fire_sched_in_preempt_notifiers(curr);
+}
+
+static void
+__fire_sched_out_preempt_notifiers(struct task_struct *curr,
+ struct task_struct *next)
+{
+ struct preempt_notifier *notifier;
+
+ hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
+ notifier->ops->sched_out(notifier, next);
+}
+
+static __always_inline void
+fire_sched_out_preempt_notifiers(struct task_struct *curr,
+ struct task_struct *next)
+{
+ if (static_branch_unlikely(&preempt_notifier_key))
+ __fire_sched_out_preempt_notifiers(curr, next);
+}
+
+#else /* !CONFIG_PREEMPT_NOTIFIERS */
+
+static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
+{
+}
+
+static inline void
+fire_sched_out_preempt_notifiers(struct task_struct *curr,
+ struct task_struct *next)
+{
+}
+
+#endif /* CONFIG_PREEMPT_NOTIFIERS */
+
+static inline void prepare_task(struct task_struct *next)
+{
+#ifdef CONFIG_SMP
+ /*
+ * Claim the task as running, we do this before switching to it
+ * such that any running task will have this set.
+ *
+ * See the ttwu() WF_ON_CPU case and its ordering comment.
+ */
+ WRITE_ONCE(next->on_cpu, 1);
+#endif
+}
+
+static inline void finish_task(struct task_struct *prev)
+{
+#ifdef CONFIG_SMP
+ /*
+ * This must be the very last reference to @prev from this CPU. After
+ * p->on_cpu is cleared, the task can be moved to a different CPU. We
+ * must ensure this doesn't happen until the switch is completely
+ * finished.
+ *
+ * In particular, the load of prev->state in finish_task_switch() must
+ * happen before this.
+ *
+ * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
+ */
+ smp_store_release(&prev->on_cpu, 0);
+#endif
+}
+
+static inline void
+prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
+{
+ /*
+ * Since the runqueue lock will be released by the next
+ * task (which is an invalid locking op but in the case
+ * of the scheduler it's an obvious special-case), so we
+ * do an early lockdep release here:
+ */
+ rq_unpin_lock(rq, rf);
+ spin_release(&rq->lock.dep_map, _THIS_IP_);
+#ifdef CONFIG_DEBUG_SPINLOCK
+ /* this is a valid case when another task releases the spinlock */
+ rq->lock.owner = next;
+#endif
+}
+
+static inline void finish_lock_switch(struct rq *rq)
+{
+ /*
+ * If we are tracking spinlock dependencies then we have to
+ * fix up the runqueue lock - which gets 'carried over' from
+ * prev into current:
+ */
+ spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
+ 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
+ * @prev: the current task that is being switched out
+ * @next: the task we are going to switch to.
+ *
+ * This is called with the rq lock held and interrupts off. It must
+ * be paired with a subsequent finish_task_switch after the context
+ * switch.
+ *
+ * prepare_task_switch sets up locking and calls architecture specific
+ * hooks.
+ */
+static inline void
+prepare_task_switch(struct rq *rq, struct task_struct *prev,
+ struct task_struct *next)
+{
+ kcov_prepare_switch(prev);
+ sched_info_switch(rq, prev, next);
+ perf_event_task_sched_out(prev, next);
+ rseq_preempt(prev);
+ fire_sched_out_preempt_notifiers(prev, next);
+ prepare_task(next);
+ prepare_arch_switch(next);
+}
+
+/**
+ * finish_task_switch - clean up after a task-switch
+ * @prev: the thread we just switched away from.
+ *
+ * finish_task_switch must be called after the context switch, paired
+ * with a prepare_task_switch call before the context switch.
+ * finish_task_switch will reconcile locking set up by prepare_task_switch,
+ * and do any other architecture-specific cleanup actions.
+ *
+ * Note that we may have delayed dropping an mm in context_switch(). If
+ * so, we finish that here outside of the runqueue lock. (Doing it
+ * with the lock held can cause deadlocks; see schedule() for
+ * details.)
+ *
+ * The context switch have flipped the stack from under us and restored the
+ * local variables which were saved when this task called schedule() in the
+ * past. prev == current is still correct but we need to recalculate this_rq
+ * because prev may have moved to another CPU.
+ */
+static struct rq *finish_task_switch(struct task_struct *prev)
+ __releases(rq->lock)
+{
+ struct rq *rq = this_rq();
+ struct mm_struct *mm = rq->prev_mm;
+ long prev_state;
+
+ /*
+ * The previous task will have left us with a preempt_count of 2
+ * because it left us after:
+ *
+ * schedule()
+ * preempt_disable(); // 1
+ * __schedule()
+ * raw_spin_lock_irq(&rq->lock) // 2
+ *
+ * Also, see FORK_PREEMPT_COUNT.
+ */
+ if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
+ "corrupted preempt_count: %s/%d/0x%x\n",
+ current->comm, current->pid, preempt_count()))
+ preempt_count_set(FORK_PREEMPT_COUNT);
+
+ rq->prev_mm = NULL;
+
+ /*
+ * A task struct has one reference for the use as "current".
+ * If a task dies, then it sets TASK_DEAD in tsk->state and calls
+ * schedule one last time. The schedule call will never return, and
+ * the scheduled task must drop that reference.
+ *
+ * We must observe prev->state before clearing prev->on_cpu (in
+ * finish_task), otherwise a concurrent wakeup can get prev
+ * running on another CPU and we could rave with its RUNNING -> DEAD
+ * transition, resulting in a double drop.
+ */
+ prev_state = prev->state;
+ vtime_task_switch(prev);
+ perf_event_task_sched_in(prev, current);
+ finish_task(prev);
+ finish_lock_switch(rq);
+ finish_arch_post_lock_switch();
+ kcov_finish_switch(current);
+
+ fire_sched_in_preempt_notifiers(current);
+ /*
+ * When switching through a kernel thread, the loop in
+ * membarrier_{private,global}_expedited() may have observed that
+ * kernel thread and not issued an IPI. It is therefore possible to
+ * schedule between user->kernel->user threads without passing though
+ * switch_mm(). Membarrier requires a barrier after storing to
+ * rq->curr, before returning to userspace, so provide them here:
+ *
+ * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
+ * provided by mmdrop(),
+ * - a sync_core for SYNC_CORE.
+ */
+ if (mm) {
+ membarrier_mm_sync_core_before_usermode(mm);
+ mmdrop(mm);
+ }
+ if (unlikely(prev_state == TASK_DEAD)) {
+ if (prev->sched_class->task_dead)
+ prev->sched_class->task_dead(prev);
+
+ /*
+ * Remove function-return probe instances associated with this
+ * task and put them back on the free list.
+ */
+ kprobe_flush_task(prev);
+
+ /* Task is done with its stack. */
+ put_task_stack(prev);
+
+ put_task_struct_rcu_user(prev);
+ }
+
+ tick_nohz_task_switch();
+ return rq;
+}
+
+#ifdef CONFIG_SMP
+
+/* rq->lock is NOT held, but preemption is disabled */
+static void __balance_callback(struct rq *rq)
+{
+ struct callback_head *head, *next;
+ void (*func)(struct rq *rq);
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&rq->lock, flags);
+ head = rq->balance_callback;
+ rq->balance_callback = NULL;
+ while (head) {
+ func = (void (*)(struct rq *))head->func;
+ next = head->next;
+ head->next = NULL;
+ head = next;
+
+ func(rq);
+ }
+ raw_spin_unlock_irqrestore(&rq->lock, flags);
+}
+
+static inline void balance_callback(struct rq *rq)
+{
+ if (unlikely(rq->balance_callback))
+ __balance_callback(rq);
+}
+
+#else
+
+static inline void balance_callback(struct rq *rq)
+{
+}
+
+#endif
+
+/**
+ * schedule_tail - first thing a freshly forked thread must call.
+ * @prev: the thread we just switched away from.
+ */
+asmlinkage __visible void schedule_tail(struct task_struct *prev)
+ __releases(rq->lock)
+{
+ struct rq *rq;
+
+ /*
+ * New tasks start with FORK_PREEMPT_COUNT, see there and
+ * finish_task_switch() for details.
+ *
+ * finish_task_switch() will drop rq->lock() and lower preempt_count
+ * and the preempt_enable() will end up enabling preemption (on
+ * PREEMPT_COUNT kernels).
+ */
+
+ rq = finish_task_switch(prev);
+ balance_callback(rq);
+ preempt_enable();
+
+ if (current->set_child_tid)
+ put_user(task_pid_vnr(current), current->set_child_tid);
+
+ calculate_sigpending();
+}
+
+/*
+ * context_switch - switch to the new MM and the new thread's register state.
+ */
+static __always_inline struct rq *
+context_switch(struct rq *rq, struct task_struct *prev,
+ struct task_struct *next, struct rq_flags *rf)
+{
+ prepare_task_switch(rq, prev, next);
+
+ /*
+ * For paravirt, this is coupled with an exit in switch_to to
+ * combine the page table reload and the switch backend into
+ * one hypercall.
+ */
+ arch_start_context_switch(prev);
+
+ /*
+ * kernel -> kernel lazy + transfer active
+ * user -> kernel lazy + mmgrab() active
+ *
+ * kernel -> user switch + mmdrop() active
+ * user -> user switch
+ */
+ if (!next->mm) { // to kernel
+ enter_lazy_tlb(prev->active_mm, next);
+
+ next->active_mm = prev->active_mm;
+ if (prev->mm) // from user
+ mmgrab(prev->active_mm);
+ else
+ prev->active_mm = NULL;
+ } else { // to user
+ membarrier_switch_mm(rq, prev->active_mm, next->mm);
+ /*
+ * sys_membarrier() requires an smp_mb() between setting
+ * rq->curr / membarrier_switch_mm() and returning to userspace.
+ *
+ * The below provides this either through switch_mm(), or in
+ * case 'prev->active_mm == next->mm' through
+ * finish_task_switch()'s mmdrop().
+ */
+ switch_mm_irqs_off(prev->active_mm, next->mm, next);
+
+ if (!prev->mm) { // from kernel
+ /* will mmdrop() in finish_task_switch(). */
+ rq->prev_mm = prev->active_mm;
+ prev->active_mm = NULL;
+ }
+ }
+
+ rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
+
+ prepare_lock_switch(rq, next, rf);
+
+ /* Here we just switch the register state and the stack. */
+ switch_to(prev, next, prev);
+ barrier();
+
+ return finish_task_switch(prev);
+}
+
+/*
+ * nr_running and nr_context_switches:
+ *
+ * externally visible scheduler statistics: current number of runnable
+ * threads, total number of context switches performed since bootup.
+ */
+unsigned long nr_running(void)
+{
+ unsigned long i, sum = 0;
+
+ for_each_online_cpu(i)
+ sum += cpu_rq(i)->nr_running;
+
+ return sum;
+}
+
+/*
+ * Check if only the current task is running on the CPU.
+ *
+ * Caution: this function does not check that the caller has disabled
+ * preemption, thus the result might have a time-of-check-to-time-of-use
+ * race. The caller is responsible to use it correctly, for example:
+ *
+ * - from a non-preemptible section (of course)
+ *
+ * - from a thread that is bound to a single CPU
+ *
+ * - in a loop with very short iterations (e.g. a polling loop)
+ */
+bool single_task_running(void)
+{
+ return raw_rq()->nr_running == 1;
+}
+EXPORT_SYMBOL(single_task_running);
+
+unsigned long long nr_context_switches(void)
+{
+ int i;
+ unsigned long long sum = 0;
+
+ for_each_possible_cpu(i)
+ sum += cpu_rq(i)->nr_switches;
+
+ return sum;
+}
+
+/*
+ * Consumers of these two interfaces, like for example the cpuidle menu
+ * governor, are using nonsensical data. Preferring shallow idle state selection
+ * for a CPU that has IO-wait which might not even end up running the task when
+ * it does become runnable.
+ */
+
+unsigned long nr_iowait_cpu(int cpu)
+{
+ return atomic_read(&cpu_rq(cpu)->nr_iowait);
+}
+
+/*
+ * IO-wait accounting, and how its mostly bollocks (on SMP).
+ *
+ * The idea behind IO-wait account is to account the idle time that we could
+ * have spend running if it were not for IO. That is, if we were to improve the
+ * storage performance, we'd have a proportional reduction in IO-wait time.
+ *
+ * This all works nicely on UP, where, when a task blocks on IO, we account
+ * idle time as IO-wait, because if the storage were faster, it could've been
+ * running and we'd not be idle.
+ *
+ * This has been extended to SMP, by doing the same for each CPU. This however
+ * is broken.
+ *
+ * Imagine for instance the case where two tasks block on one CPU, only the one
+ * CPU will have IO-wait accounted, while the other has regular idle. Even
+ * though, if the storage were faster, both could've ran at the same time,
+ * utilising both CPUs.
+ *
+ * This means, that when looking globally, the current IO-wait accounting on
+ * SMP is a lower bound, by reason of under accounting.
+ *
+ * Worse, since the numbers are provided per CPU, they are sometimes
+ * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
+ * associated with any one particular CPU, it can wake to another CPU than it
+ * blocked on. This means the per CPU IO-wait number is meaningless.
+ *
+ * Task CPU affinities can make all that even more 'interesting'.
+ */
+
+unsigned long nr_iowait(void)
+{
+ unsigned long i, sum = 0;
+
+ for_each_possible_cpu(i)
+ sum += nr_iowait_cpu(i);
+
+ return sum;
+}
+
+#ifdef CONFIG_SMP
+
+/*
+ * sched_exec - execve() is a valuable balancing opportunity, because at
+ * this point the task has the smallest effective memory and cache footprint.
+ */
+void sched_exec(void)
+{
+ struct task_struct *p = current;
+ unsigned long flags;
+ int dest_cpu;
+
+ raw_spin_lock_irqsave(&p->pi_lock, flags);
+ dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
+ if (dest_cpu == smp_processor_id())
+ goto unlock;
+
+ if (likely(cpu_active(dest_cpu))) {
+ struct migration_arg arg = { p, dest_cpu };
+
+ raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+ stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
+ return;
+ }
+unlock:
+ raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+}
+
+#endif
+
+DEFINE_PER_CPU(struct kernel_stat, kstat);
+DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
+
+EXPORT_PER_CPU_SYMBOL(kstat);
+EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
+
+/*
+ * The function fair_sched_class.update_curr accesses the struct curr
+ * and its field curr->exec_start; when called from task_sched_runtime(),
+ * we observe a high rate of cache misses in practice.
+ * Prefetching this data results in improved performance.
+ */
+static inline void prefetch_curr_exec_start(struct task_struct *p)
+{
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ struct sched_entity *curr = (&p->se)->cfs_rq->curr;
+#else
+ struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
+#endif
+ prefetch(curr);
+ prefetch(&curr->exec_start);
+}
+
+/*
+ * Return accounted runtime for the task.
+ * In case the task is currently running, return the runtime plus current's
+ * pending runtime that have not been accounted yet.
+ */
+unsigned long long task_sched_runtime(struct task_struct *p)
+{
+ struct rq_flags rf;
+ struct rq *rq;
+ u64 ns;
+
+#if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
+ /*
+ * 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.
+ *
+ * If we race with it leaving CPU, we'll take a lock. So we're correct.
+ * If we race with it entering CPU, unaccounted time is 0. This is
+ * indistinguishable from the read occurring a few cycles earlier.
+ * If we see ->on_cpu without ->on_rq, the task is leaving, and has
+ * been accounted, so we're correct here as well.
+ */
+ if (!p->on_cpu || !task_on_rq_queued(p))
+ return p->se.sum_exec_runtime;
+#endif
+
+ rq = task_rq_lock(p, &rf);
+ /*
+ * Must be ->curr _and_ ->on_rq. If dequeued, we would
+ * project cycles that may never be accounted to this
+ * thread, breaking clock_gettime().
+ */
+ if (task_current(rq, p) && task_on_rq_queued(p)) {
+ prefetch_curr_exec_start(p);
+ update_rq_clock(rq);
+ p->sched_class->update_curr(rq);
+ }
+ ns = p->se.sum_exec_runtime;
+ task_rq_unlock(rq, p, &rf);
+
+ return ns;
+}
+
+/*
+ * This function gets called by the timer code, with HZ frequency.
+ * We call it with interrupts disabled.
+ */
+void scheduler_tick(void)
+{
+ int cpu = smp_processor_id();
+ struct rq *rq = cpu_rq(cpu);
+ struct task_struct *curr = rq->curr;
+ struct rq_flags rf;
+ unsigned long thermal_pressure;
+
+ arch_scale_freq_tick();
+ sched_clock_tick();
+
+ rq_lock(rq, &rf);
+
+ update_rq_clock(rq);
+ thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
+ update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure);
+ curr->sched_class->task_tick(rq, curr, 0);
+ calc_global_load_tick(rq);
+ psi_task_tick(rq);
+
+ rq_unlock(rq, &rf);
+
+ perf_event_task_tick();
+
+#ifdef CONFIG_SMP
+ rq->idle_balance = idle_cpu(cpu);
+ trigger_load_balance(rq);
+#endif
+}
+
+#ifdef CONFIG_NO_HZ_FULL
+
+struct tick_work {
+ int cpu;
+ atomic_t state;
+ struct delayed_work work;
+};
+/* Values for ->state, see diagram below. */
+#define TICK_SCHED_REMOTE_OFFLINE 0
+#define TICK_SCHED_REMOTE_OFFLINING 1
+#define TICK_SCHED_REMOTE_RUNNING 2
+
+/*
+ * State diagram for ->state:
+ *
+ *
+ * TICK_SCHED_REMOTE_OFFLINE
+ * | ^
+ * | |
+ * | | sched_tick_remote()
+ * | |
+ * | |
+ * +--TICK_SCHED_REMOTE_OFFLINING
+ * | ^
+ * | |
+ * sched_tick_start() | | sched_tick_stop()
+ * | |
+ * V |
+ * TICK_SCHED_REMOTE_RUNNING
+ *
+ *
+ * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote()
+ * and sched_tick_start() are happy to leave the state in RUNNING.
+ */
+
+static struct tick_work __percpu *tick_work_cpu;
+
+static void sched_tick_remote(struct work_struct *work)
+{
+ 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 task_struct *curr;
+ struct rq_flags rf;
+ u64 delta;
+ int os;
+
+ /*
+ * 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 (!tick_nohz_tick_stopped_cpu(cpu))
+ goto out_requeue;
+
+ rq_lock_irq(rq, &rf);
+ curr = rq->curr;
+ if (cpu_is_offline(cpu))
+ goto out_unlock;
+
+ update_rq_clock(rq);
+
+ if (!is_idle_task(curr)) {
+ /*
+ * Make sure the next tick runs within a reasonable
+ * amount of time.
+ */
+ delta = rq_clock_task(rq) - curr->se.exec_start;
+ WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
+ }
+ curr->sched_class->task_tick(rq, curr, 0);
+
+ calc_load_nohz_remote(rq);
+out_unlock:
+ rq_unlock_irq(rq, &rf);
+out_requeue:
+
+ /*
+ * 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. But
+ * first update state to reflect hotplug activity if required.
+ */
+ os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING);
+ WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE);
+ if (os == TICK_SCHED_REMOTE_RUNNING)
+ queue_delayed_work(system_unbound_wq, dwork, HZ);
+}
+
+static void sched_tick_start(int cpu)
+{
+ int os;
+ 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);
+ os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING);
+ WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING);
+ if (os == TICK_SCHED_REMOTE_OFFLINE) {
+ 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;
+ int os;
+
+ if (housekeeping_cpu(cpu, HK_FLAG_TICK))
+ return;
+
+ WARN_ON_ONCE(!tick_work_cpu);
+
+ twork = per_cpu_ptr(tick_work_cpu, cpu);
+ /* There cannot be competing actions, but don't rely on stop-machine. */
+ os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING);
+ WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING);
+ /* Don't cancel, as this would mess up the state machine. */
+}
+#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_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
+ defined(CONFIG_TRACE_PREEMPT_TOGGLE))
+/*
+ * If the value passed in is equal to the current preempt count
+ * then we just disabled preemption. Start timing the latency.
+ */
+static inline void preempt_latency_start(int val)
+{
+ if (preempt_count() == val) {
+ unsigned long ip = get_lock_parent_ip();
+#ifdef CONFIG_DEBUG_PREEMPT
+ current->preempt_disable_ip = ip;
+#endif
+ trace_preempt_off(CALLER_ADDR0, ip);
+ }
+}
+
+void preempt_count_add(int val)
+{
+#ifdef CONFIG_DEBUG_PREEMPT
+ /*
+ * Underflow?
+ */
+ if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
+ return;
+#endif
+ __preempt_count_add(val);
+#ifdef CONFIG_DEBUG_PREEMPT
+ /*
+ * Spinlock count overflowing soon?
+ */
+ DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
+ PREEMPT_MASK - 10);
+#endif
+ preempt_latency_start(val);
+}
+EXPORT_SYMBOL(preempt_count_add);
+NOKPROBE_SYMBOL(preempt_count_add);
+
+/*
+ * If the value passed in equals to the current preempt count
+ * then we just enabled preemption. Stop timing the latency.
+ */
+static inline void preempt_latency_stop(int val)
+{
+ if (preempt_count() == val)
+ trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
+}
+
+void preempt_count_sub(int val)
+{
+#ifdef CONFIG_DEBUG_PREEMPT
+ /*
+ * Underflow?
+ */
+ if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
+ return;
+ /*
+ * Is the spinlock portion underflowing?
+ */
+ if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
+ !(preempt_count() & PREEMPT_MASK)))
+ return;
+#endif
+
+ preempt_latency_stop(val);
+ __preempt_count_sub(val);
+}
+EXPORT_SYMBOL(preempt_count_sub);
+NOKPROBE_SYMBOL(preempt_count_sub);
+
+#else
+static inline void preempt_latency_start(int val) { }
+static inline void preempt_latency_stop(int val) { }
+#endif
+
+static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
+{
+#ifdef CONFIG_DEBUG_PREEMPT
+ return p->preempt_disable_ip;
+#else
+ return 0;
+#endif
+}
+
+/*
+ * Print scheduling while atomic bug:
+ */
+static noinline void __schedule_bug(struct task_struct *prev)
+{
+ /* Save this before calling printk(), since that will clobber it */
+ unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
+
+ if (oops_in_progress)
+ return;
+
+ printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
+ prev->comm, prev->pid, preempt_count());
+
+ debug_show_held_locks(prev);
+ print_modules();
+ if (irqs_disabled())
+ print_irqtrace_events(prev);
+ if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
+ && in_atomic_preempt_off()) {
+ pr_err("Preemption disabled at:");
+ print_ip_sym(KERN_ERR, preempt_disable_ip);
+ }
+ check_panic_on_warn("scheduling while atomic");
+
+ dump_stack();
+ add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
+}
+
+/*
+ * Various schedule()-time debugging checks and statistics:
+ */
+static inline void schedule_debug(struct task_struct *prev, bool preempt)
+{
+#ifdef CONFIG_SCHED_STACK_END_CHECK
+ if (task_stack_end_corrupted(prev))
+ panic("corrupted stack end detected inside scheduler\n");
+
+ if (task_scs_end_corrupted(prev))
+ panic("corrupted shadow stack detected inside scheduler\n");
+#endif
+
+#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
+ if (!preempt && prev->state && prev->non_block_count) {
+ printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n",
+ prev->comm, prev->pid, prev->non_block_count);
+ dump_stack();
+ add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
+ }
+#endif
+
+ if (unlikely(in_atomic_preempt_off())) {
+ __schedule_bug(prev);
+ preempt_count_set(PREEMPT_DISABLED);
+ }
+ rcu_sleep_check();
+
+ profile_hit(SCHED_PROFILING, __builtin_return_address(0));
+
+ schedstat_inc(this_rq()->sched_count);
+}
+
+static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
+ struct rq_flags *rf)
+{
+#ifdef CONFIG_SMP
+ const struct sched_class *class;
+ /*
+ * We must do the balancing pass before put_prev_task(), such
+ * that when we release the rq->lock the task is in the same
+ * state as before we took rq->lock.
+ *
+ * We can terminate the balance pass as soon as we know there is
+ * a runnable task of @class priority or higher.
+ */
+ for_class_range(class, prev->sched_class, &idle_sched_class) {
+ if (class->balance(rq, prev, rf))
+ break;
+ }
+#endif
+
+ put_prev_task(rq, prev);
+}
+
+/*
+ * Pick up the highest-prio task:
+ */
+static inline struct task_struct *
+pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+{
+ const struct sched_class *class;
+ struct task_struct *p;
+
+ /*
+ * Optimization: we know that if all tasks are in the fair class we can
+ * call that function directly, but only if the @prev task wasn't of a
+ * higher scheduling class, because otherwise those loose the
+ * opportunity to pull in more work from other CPUs.
+ */
+ if (likely(prev->sched_class <= &fair_sched_class &&
+ rq->nr_running == rq->cfs.h_nr_running)) {
+
+ p = pick_next_task_fair(rq, prev, rf);
+ if (unlikely(p == RETRY_TASK))
+ goto restart;
+
+ /* Assumes fair_sched_class->next == idle_sched_class */
+ if (!p) {
+ put_prev_task(rq, prev);
+ p = pick_next_task_idle(rq);
+ }
+
+ return p;
+ }
+
+restart:
+ put_prev_task_balance(rq, prev, rf);
+
+ for_each_class(class) {
+ p = class->pick_next_task(rq);
+ if (p)
+ return p;
+ }
+
+ /* The idle class should always have a runnable task: */
+ BUG();
+}
+
+/*
+ * __schedule() is the main scheduler function.
+ *
+ * The main means of driving the scheduler and thus entering this function are:
+ *
+ * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
+ *
+ * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
+ * paths. For example, see arch/x86/entry_64.S.
+ *
+ * To drive preemption between tasks, the scheduler sets the flag in timer
+ * interrupt handler scheduler_tick().
+ *
+ * 3. Wakeups don't really cause entry into schedule(). They add a
+ * task to the run-queue and that's it.
+ *
+ * Now, if the new task added to the run-queue preempts the current
+ * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
+ * called on the nearest possible occasion:
+ *
+ * - If the kernel is preemptible (CONFIG_PREEMPTION=y):
+ *
+ * - in syscall or exception context, at the next outmost
+ * preempt_enable(). (this might be as soon as the wake_up()'s
+ * spin_unlock()!)
+ *
+ * - in IRQ context, return from interrupt-handler to
+ * preemptible context
+ *
+ * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
+ * then at the next:
+ *
+ * - cond_resched() call
+ * - explicit schedule() call
+ * - return from syscall or exception to user-space
+ * - return from interrupt-handler to user-space
+ *
+ * WARNING: must be called with preemption disabled!
+ */
+static void __sched notrace __schedule(bool preempt)
+{
+ struct task_struct *prev, *next;
+ unsigned long *switch_count;
+ unsigned long prev_state;
+ struct rq_flags rf;
+ struct rq *rq;
+ int cpu;
+
+ cpu = smp_processor_id();
+ rq = cpu_rq(cpu);
+ prev = rq->curr;
+
+ schedule_debug(prev, preempt);
+
+ if (sched_feat(HRTICK))
+ hrtick_clear(rq);
+
+ local_irq_disable();
+ rcu_note_context_switch(preempt);
+
+ /*
+ * Make sure that signal_pending_state()->signal_pending() below
+ * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
+ * done by the caller to avoid the race with signal_wake_up():
+ *
+ * __set_current_state(@state) signal_wake_up()
+ * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING)
+ * wake_up_state(p, state)
+ * LOCK rq->lock LOCK p->pi_state
+ * smp_mb__after_spinlock() smp_mb__after_spinlock()
+ * if (signal_pending_state()) if (p->state & @state)
+ *
+ * Also, the membarrier system call requires a full memory barrier
+ * after coming from user-space, before storing to rq->curr.
+ */
+ rq_lock(rq, &rf);
+ smp_mb__after_spinlock();
+
+ /* Promote REQ to ACT */
+ rq->clock_update_flags <<= 1;
+ update_rq_clock(rq);
+
+ switch_count = &prev->nivcsw;
+
+ /*
+ * We must load prev->state once (task_struct::state is volatile), such
+ * that:
+ *
+ * - we form a control dependency vs deactivate_task() below.
+ * - ptrace_{,un}freeze_traced() can change ->state underneath us.
+ */
+ prev_state = prev->state;
+ if (!preempt && prev_state) {
+ if (signal_pending_state(prev_state, prev)) {
+ prev->state = TASK_RUNNING;
+ } else {
+ prev->sched_contributes_to_load =
+ (prev_state & TASK_UNINTERRUPTIBLE) &&
+ !(prev_state & TASK_NOLOAD) &&
+ !(prev->flags & PF_FROZEN);
+
+ if (prev->sched_contributes_to_load)
+ rq->nr_uninterruptible++;
+
+ /*
+ * __schedule() ttwu()
+ * prev_state = prev->state; if (p->on_rq && ...)
+ * if (prev_state) goto out;
+ * p->on_rq = 0; smp_acquire__after_ctrl_dep();
+ * p->state = TASK_WAKING
+ *
+ * Where __schedule() and ttwu() have matching control dependencies.
+ *
+ * After this, schedule() must not care about p->state any more.
+ */
+ deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
+
+ if (prev->in_iowait) {
+ atomic_inc(&rq->nr_iowait);
+ delayacct_blkio_start();
+ }
+ }
+ switch_count = &prev->nvcsw;
+ }
+
+ next = pick_next_task(rq, prev, &rf);
+ clear_tsk_need_resched(prev);
+ clear_preempt_need_resched();
+
+ if (likely(prev != next)) {
+ rq->nr_switches++;
+ /*
+ * RCU users of rcu_dereference(rq->curr) may not see
+ * changes to task_struct made by pick_next_task().
+ */
+ RCU_INIT_POINTER(rq->curr, next);
+ /*
+ * The membarrier system call requires each architecture
+ * to have a full memory barrier after updating
+ * rq->curr, before returning to user-space.
+ *
+ * Here are the schemes providing that barrier on the
+ * various architectures:
+ * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
+ * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
+ * - finish_lock_switch() for weakly-ordered
+ * architectures where spin_unlock is a full barrier,
+ * - switch_to() for arm64 (weakly-ordered, spin_unlock
+ * is a RELEASE barrier),
+ */
+ ++*switch_count;
+
+ psi_sched_switch(prev, next, !task_on_rq_queued(prev));
+
+ trace_sched_switch(preempt, prev, next);
+
+ /* Also unlocks the rq: */
+ rq = context_switch(rq, prev, next, &rf);
+ } else {
+ rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
+ rq_unlock_irq(rq, &rf);
+ }
+
+ balance_callback(rq);
+}
+
+void __noreturn do_task_dead(void)
+{
+ /* Causes final put_task_struct in finish_task_switch(): */
+ set_special_state(TASK_DEAD);
+
+ /* Tell freezer to ignore us: */
+ current->flags |= PF_NOFREEZE;
+
+ __schedule(false);
+ BUG();
+
+ /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
+ for (;;)
+ cpu_relax();
+}
+
+static inline void sched_submit_work(struct task_struct *tsk)
+{
+ unsigned int task_flags;
+
+ if (!tsk->state)
+ return;
+
+ task_flags = tsk->flags;
+ /*
+ * If a worker went to sleep, notify and ask workqueue whether
+ * it wants to wake up a task to maintain concurrency.
+ * As this function is called inside the schedule() context,
+ * we disable preemption to avoid it calling schedule() again
+ * in the possible wakeup of a kworker and because wq_worker_sleeping()
+ * requires it.
+ */
+ if (task_flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
+ preempt_disable();
+ if (task_flags & PF_WQ_WORKER)
+ wq_worker_sleeping(tsk);
+ else
+ io_wq_worker_sleeping(tsk);
+ preempt_enable_no_resched();
+ }
+
+ if (tsk_is_pi_blocked(tsk))
+ return;
+
+ /*
+ * If we are going to sleep and we have plugged IO queued,
+ * make sure to submit it to avoid deadlocks.
+ */
+ if (blk_needs_flush_plug(tsk))
+ blk_schedule_flush_plug(tsk);
+}
+
+static void sched_update_worker(struct task_struct *tsk)
+{
+ if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
+ if (tsk->flags & PF_WQ_WORKER)
+ wq_worker_running(tsk);
+ else
+ io_wq_worker_running(tsk);
+ }
+}
+
+asmlinkage __visible void __sched schedule(void)
+{
+ struct task_struct *tsk = current;
+
+ sched_submit_work(tsk);
+ do {
+ preempt_disable();
+ __schedule(false);
+ sched_preempt_enable_no_resched();
+ } while (need_resched());
+ sched_update_worker(tsk);
+}
+EXPORT_SYMBOL(schedule);
+
+/*
+ * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
+ * state (have scheduled out non-voluntarily) by making sure that all
+ * tasks have either left the run queue or have gone into user space.
+ * As idle tasks do not do either, they must not ever be preempted
+ * (schedule out non-voluntarily).
+ *
+ * schedule_idle() is similar to schedule_preempt_disable() except that it
+ * never enables preemption because it does not call sched_submit_work().
+ */
+void __sched schedule_idle(void)
+{
+ /*
+ * As this skips calling sched_submit_work(), which the idle task does
+ * regardless because that function is a nop when the task is in a
+ * TASK_RUNNING state, make sure this isn't used someplace that the
+ * current task can be in any other state. Note, idle is always in the
+ * TASK_RUNNING state.
+ */
+ WARN_ON_ONCE(current->state);
+ do {
+ __schedule(false);
+ } while (need_resched());
+}
+
+#ifdef CONFIG_CONTEXT_TRACKING
+asmlinkage __visible void __sched schedule_user(void)
+{
+ /*
+ * If we come here after a random call to set_need_resched(),
+ * or we have been woken up remotely but the IPI has not yet arrived,
+ * we haven't yet exited the RCU idle mode. Do it here manually until
+ * we find a better solution.
+ *
+ * NB: There are buggy callers of this function. Ideally we
+ * should warn if prev_state != CONTEXT_USER, but that will trigger
+ * too frequently to make sense yet.
+ */
+ enum ctx_state prev_state = exception_enter();
+ schedule();
+ exception_exit(prev_state);
+}
+#endif
+
+/**
+ * schedule_preempt_disabled - called with preemption disabled
+ *
+ * Returns with preemption disabled. Note: preempt_count must be 1
+ */
+void __sched schedule_preempt_disabled(void)
+{
+ sched_preempt_enable_no_resched();
+ schedule();
+ preempt_disable();
+}
+
+static void __sched notrace preempt_schedule_common(void)
+{
+ do {
+ /*
+ * Because the function tracer can trace preempt_count_sub()
+ * and it also uses preempt_enable/disable_notrace(), if
+ * NEED_RESCHED is set, the preempt_enable_notrace() called
+ * by the function tracer will call this function again and
+ * cause infinite recursion.
+ *
+ * Preemption must be disabled here before the function
+ * tracer can trace. Break up preempt_disable() into two
+ * calls. One to disable preemption without fear of being
+ * traced. The other to still record the preemption latency,
+ * which can also be traced by the function tracer.
+ */
+ preempt_disable_notrace();
+ preempt_latency_start(1);
+ __schedule(true);
+ preempt_latency_stop(1);
+ preempt_enable_no_resched_notrace();
+
+ /*
+ * Check again in case we missed a preemption opportunity
+ * between schedule and now.
+ */
+ } while (need_resched());
+}
+
+#ifdef CONFIG_PREEMPTION
+/*
+ * This is the entry point to schedule() from in-kernel preemption
+ * off of preempt_enable.
+ */
+asmlinkage __visible void __sched notrace preempt_schedule(void)
+{
+ /*
+ * If there is a non-zero preempt_count or interrupts are disabled,
+ * we do not want to preempt the current task. Just return..
+ */
+ if (likely(!preemptible()))
+ return;
+
+ preempt_schedule_common();
+}
+NOKPROBE_SYMBOL(preempt_schedule);
+EXPORT_SYMBOL(preempt_schedule);
+
+/**
+ * preempt_schedule_notrace - preempt_schedule called by tracing
+ *
+ * The tracing infrastructure uses preempt_enable_notrace to prevent
+ * recursion and tracing preempt enabling caused by the tracing
+ * infrastructure itself. But as tracing can happen in areas coming
+ * from userspace or just about to enter userspace, a preempt enable
+ * can occur before user_exit() is called. This will cause the scheduler
+ * to be called when the system is still in usermode.
+ *
+ * To prevent this, the preempt_enable_notrace will use this function
+ * instead of preempt_schedule() to exit user context if needed before
+ * calling the scheduler.
+ */
+asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
+{
+ enum ctx_state prev_ctx;
+
+ if (likely(!preemptible()))
+ return;
+
+ do {
+ /*
+ * Because the function tracer can trace preempt_count_sub()
+ * and it also uses preempt_enable/disable_notrace(), if
+ * NEED_RESCHED is set, the preempt_enable_notrace() called
+ * by the function tracer will call this function again and
+ * cause infinite recursion.
+ *
+ * Preemption must be disabled here before the function
+ * tracer can trace. Break up preempt_disable() into two
+ * calls. One to disable preemption without fear of being
+ * traced. The other to still record the preemption latency,
+ * which can also be traced by the function tracer.
+ */
+ preempt_disable_notrace();
+ preempt_latency_start(1);
+ /*
+ * Needs preempt disabled in case user_exit() is traced
+ * and the tracer calls preempt_enable_notrace() causing
+ * an infinite recursion.
+ */
+ prev_ctx = exception_enter();
+ __schedule(true);
+ exception_exit(prev_ctx);
+
+ preempt_latency_stop(1);
+ preempt_enable_no_resched_notrace();
+ } while (need_resched());
+}
+EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
+
+#endif /* CONFIG_PREEMPTION */
+
+/*
+ * This is the entry point to schedule() from kernel preemption
+ * off of irq context.
+ * Note, that this is called and return with irqs disabled. This will
+ * protect us against recursive calling from irq.
+ */
+asmlinkage __visible void __sched preempt_schedule_irq(void)
+{
+ enum ctx_state prev_state;
+
+ /* Catch callers which need to be fixed */
+ BUG_ON(preempt_count() || !irqs_disabled());
+
+ prev_state = exception_enter();
+
+ do {
+ preempt_disable();
+ local_irq_enable();
+ __schedule(true);
+ local_irq_disable();
+ sched_preempt_enable_no_resched();
+ } while (need_resched());
+
+ exception_exit(prev_state);
+}
+
+int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
+ void *key)
+{
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~WF_SYNC);
+ return try_to_wake_up(curr->private, mode, wake_flags);
+}
+EXPORT_SYMBOL(default_wake_function);
+
+static void __setscheduler_prio(struct task_struct *p, int prio)
+{
+ if (dl_prio(prio))
+ p->sched_class = &dl_sched_class;
+ else if (rt_prio(prio))
+ p->sched_class = &rt_sched_class;
+ else
+ p->sched_class = &fair_sched_class;
+
+ p->prio = prio;
+}
+
+#ifdef CONFIG_RT_MUTEXES
+
+static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
+{
+ if (pi_task)
+ prio = min(prio, pi_task->prio);
+
+ return prio;
+}
+
+static inline int rt_effective_prio(struct task_struct *p, int prio)
+{
+ struct task_struct *pi_task = rt_mutex_get_top_task(p);
+
+ return __rt_effective_prio(pi_task, prio);
+}
+
+/*
+ * rt_mutex_setprio - set the current priority of a task
+ * @p: task to boost
+ * @pi_task: donor task
+ *
+ * This function changes the 'effective' priority of a task. It does
+ * not touch ->normal_prio like __setscheduler().
+ *
+ * Used by the rt_mutex code to implement priority inheritance
+ * logic. Call site only calls if the priority of the task changed.
+ */
+void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
+{
+ int prio, oldprio, queued, running, queue_flag =
+ DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
+ const struct sched_class *prev_class;
+ struct rq_flags rf;
+ struct rq *rq;
+
+ /* XXX used to be waiter->prio, not waiter->task->prio */
+ prio = __rt_effective_prio(pi_task, p->normal_prio);
+
+ /*
+ * If nothing changed; bail early.
+ */
+ if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
+ return;
+
+ rq = __task_rq_lock(p, &rf);
+ update_rq_clock(rq);
+ /*
+ * Set under pi_lock && rq->lock, such that the value can be used under
+ * either lock.
+ *
+ * Note that there is loads of tricky to make this pointer cache work
+ * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
+ * ensure a task is de-boosted (pi_task is set to NULL) before the
+ * task is allowed to run again (and can exit). This ensures the pointer
+ * points to a blocked task -- which guaratees the task is present.
+ */
+ p->pi_top_task = pi_task;
+
+ /*
+ * For FIFO/RR we only need to set prio, if that matches we're done.
+ */
+ if (prio == p->prio && !dl_prio(prio))
+ goto out_unlock;
+
+ /*
+ * Idle task boosting is a nono in general. There is one
+ * exception, when PREEMPT_RT and NOHZ is active:
+ *
+ * The idle task calls get_next_timer_interrupt() and holds
+ * the timer wheel base->lock on the CPU and another CPU wants
+ * to access the timer (probably to cancel it). We can safely
+ * ignore the boosting request, as the idle CPU runs this code
+ * with interrupts disabled and will complete the lock
+ * protected section without being interrupted. So there is no
+ * real need to boost.
+ */
+ if (unlikely(p == rq->idle)) {
+ WARN_ON(p != rq->curr);
+ WARN_ON(p->pi_blocked_on);
+ goto out_unlock;
+ }
+
+ trace_sched_pi_setprio(p, pi_task);
+ oldprio = p->prio;
+
+ if (oldprio == prio)
+ queue_flag &= ~DEQUEUE_MOVE;
+
+ prev_class = p->sched_class;
+ queued = task_on_rq_queued(p);
+ running = task_current(rq, p);
+ if (queued)
+ dequeue_task(rq, p, queue_flag);
+ if (running)
+ put_prev_task(rq, p);
+
+ /*
+ * Boosting condition are:
+ * 1. -rt task is running and holds mutex A
+ * --> -dl task blocks on mutex A
+ *
+ * 2. -dl task is running and holds mutex A
+ * --> -dl task blocks on mutex A and could preempt the
+ * running task
+ */
+ if (dl_prio(prio)) {
+ if (!dl_prio(p->normal_prio) ||
+ (pi_task && dl_prio(pi_task->prio) &&
+ dl_entity_preempt(&pi_task->dl, &p->dl))) {
+ p->dl.pi_se = pi_task->dl.pi_se;
+ queue_flag |= ENQUEUE_REPLENISH;
+ } else {
+ p->dl.pi_se = &p->dl;
+ }
+ } else if (rt_prio(prio)) {
+ if (dl_prio(oldprio))
+ p->dl.pi_se = &p->dl;
+ if (oldprio < prio)
+ queue_flag |= ENQUEUE_HEAD;
+ } else {
+ if (dl_prio(oldprio))
+ p->dl.pi_se = &p->dl;
+ if (rt_prio(oldprio))
+ p->rt.timeout = 0;
+ }
+
+ __setscheduler_prio(p, prio);
+
+ if (queued)
+ enqueue_task(rq, p, queue_flag);
+ if (running)
+ set_next_task(rq, p);
+
+ check_class_changed(rq, p, prev_class, oldprio);
+out_unlock:
+ /* Avoid rq from going away on us: */
+ preempt_disable();
+ __task_rq_unlock(rq, &rf);
+
+ balance_callback(rq);
+ preempt_enable();
+}
+#else
+static inline int rt_effective_prio(struct task_struct *p, int prio)
+{
+ return prio;
+}
+#endif
+
+void set_user_nice(struct task_struct *p, long nice)
+{
+ bool queued, running;
+ int old_prio;
+ struct rq_flags rf;
+ struct rq *rq;
+
+ if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
+ return;
+ /*
+ * We have to be careful, if called from sys_setpriority(),
+ * the task might be in the middle of scheduling on another CPU.
+ */
+ rq = task_rq_lock(p, &rf);
+ update_rq_clock(rq);
+
+ /*
+ * The RT priorities are set via sched_setscheduler(), but we still
+ * allow the 'normal' nice value to be set - but as expected
+ * it wont have any effect on scheduling until the task is
+ * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
+ */
+ if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
+ p->static_prio = NICE_TO_PRIO(nice);
+ goto out_unlock;
+ }
+ queued = task_on_rq_queued(p);
+ running = task_current(rq, p);
+ if (queued)
+ dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
+ if (running)
+ put_prev_task(rq, p);
+
+ p->static_prio = NICE_TO_PRIO(nice);
+ set_load_weight(p);
+ old_prio = p->prio;
+ p->prio = effective_prio(p);
+
+ if (queued)
+ enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
+ if (running)
+ set_next_task(rq, p);
+
+ /*
+ * If the task increased its priority or is running and
+ * lowered its priority, then reschedule its CPU:
+ */
+ p->sched_class->prio_changed(rq, p, old_prio);
+
+out_unlock:
+ task_rq_unlock(rq, p, &rf);
+}
+EXPORT_SYMBOL(set_user_nice);
+
+/*
+ * can_nice - check if a task can reduce its nice value
+ * @p: task
+ * @nice: nice value
+ */
+int can_nice(const struct task_struct *p, const int nice)
+{
+ /* Convert nice value [19,-20] to rlimit style value [1,40]: */
+ int nice_rlim = nice_to_rlimit(nice);
+
+ return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
+ capable(CAP_SYS_NICE));
+}
+
+#ifdef __ARCH_WANT_SYS_NICE
+
+/*
+ * sys_nice - change the priority of the current process.
+ * @increment: priority increment
+ *
+ * sys_setpriority is a more generic, but much slower function that
+ * does similar things.
+ */
+SYSCALL_DEFINE1(nice, int, increment)
+{
+ long nice, retval;
+
+ /*
+ * Setpriority might change our priority at the same moment.
+ * We don't have to worry. Conceptually one call occurs first
+ * and we have a single winner.
+ */
+ increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
+ nice = task_nice(current) + increment;
+
+ nice = clamp_val(nice, MIN_NICE, MAX_NICE);
+ if (increment < 0 && !can_nice(current, nice))
+ return -EPERM;
+
+ retval = security_task_setnice(current, nice);
+ if (retval)
+ return retval;
+
+ set_user_nice(current, nice);
+ return 0;
+}
+
+#endif
+
+/**
+ * task_prio - return the priority value of a given task.
+ * @p: the task in question.
+ *
+ * Return: The priority value as seen by users in /proc.
+ * RT tasks are offset by -200. Normal tasks are centered
+ * around 0, value goes from -16 to +15.
+ */
+int task_prio(const struct task_struct *p)
+{
+ return p->prio - MAX_RT_PRIO;
+}
+
+/**
+ * idle_cpu - is a given CPU idle currently?
+ * @cpu: the processor in question.
+ *
+ * Return: 1 if the CPU is currently idle. 0 otherwise.
+ */
+int idle_cpu(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ if (rq->curr != rq->idle)
+ return 0;
+
+ if (rq->nr_running)
+ return 0;
+
+#ifdef CONFIG_SMP
+ if (rq->ttwu_pending)
+ return 0;
+#endif
+
+ return 1;
+}
+
+/**
+ * available_idle_cpu - is a given CPU idle for enqueuing work.
+ * @cpu: the CPU in question.
+ *
+ * Return: 1 if the CPU is currently idle. 0 otherwise.
+ */
+int available_idle_cpu(int cpu)
+{
+ if (!idle_cpu(cpu))
+ return 0;
+
+ if (vcpu_is_preempted(cpu))
+ return 0;
+
+ return 1;
+}
+
+/**
+ * idle_task - return the idle task for a given CPU.
+ * @cpu: the processor in question.
+ *
+ * Return: The idle task for the CPU @cpu.
+ */
+struct task_struct *idle_task(int cpu)
+{
+ return cpu_rq(cpu)->idle;
+}
+
+/**
+ * find_process_by_pid - find a process with a matching PID value.
+ * @pid: the pid in question.
+ *
+ * The task of @pid, if found. %NULL otherwise.
+ */
+static struct task_struct *find_process_by_pid(pid_t pid)
+{
+ return pid ? find_task_by_vpid(pid) : current;
+}
+
+/*
+ * sched_setparam() passes in -1 for its policy, to let the functions
+ * it calls know not to change it.
+ */
+#define SETPARAM_POLICY -1
+
+static void __setscheduler_params(struct task_struct *p,
+ const struct sched_attr *attr)
+{
+ int policy = attr->sched_policy;
+
+ if (policy == SETPARAM_POLICY)
+ policy = p->policy;
+
+ p->policy = policy;
+
+ if (dl_policy(policy))
+ __setparam_dl(p, attr);
+ else if (fair_policy(policy))
+ p->static_prio = NICE_TO_PRIO(attr->sched_nice);
+
+ /*
+ * __sched_setscheduler() ensures attr->sched_priority == 0 when
+ * !rt_policy. Always setting this ensures that things like
+ * getparam()/getattr() don't report silly values for !rt tasks.
+ */
+ p->rt_priority = attr->sched_priority;
+ p->normal_prio = normal_prio(p);
+ set_load_weight(p);
+}
+
+/*
+ * Check the target process has a UID that matches the current process's:
+ */
+static bool check_same_owner(struct task_struct *p)
+{
+ const struct cred *cred = current_cred(), *pcred;
+ bool match;
+
+ rcu_read_lock();
+ pcred = __task_cred(p);
+ match = (uid_eq(cred->euid, pcred->euid) ||
+ uid_eq(cred->euid, pcred->uid));
+ rcu_read_unlock();
+ return match;
+}
+
+static int __sched_setscheduler(struct task_struct *p,
+ const struct sched_attr *attr,
+ bool user, bool pi)
+{
+ int oldpolicy = -1, policy = attr->sched_policy;
+ int retval, oldprio, newprio, queued, running;
+ const struct sched_class *prev_class;
+ struct rq_flags rf;
+ int reset_on_fork;
+ int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
+ struct rq *rq;
+ bool cpuset_locked = false;
+
+ /* The pi code expects interrupts enabled */
+ BUG_ON(pi && in_interrupt());
+recheck:
+ /* Double check policy once rq lock held: */
+ if (policy < 0) {
+ reset_on_fork = p->sched_reset_on_fork;
+ policy = oldpolicy = p->policy;
+ } else {
+ reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
+
+ if (!valid_policy(policy))
+ return -EINVAL;
+ }
+
+ if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
+ return -EINVAL;
+
+ /*
+ * Valid priorities for SCHED_FIFO and SCHED_RR are
+ * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
+ * SCHED_BATCH and SCHED_IDLE is 0.
+ */
+ if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
+ (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
+ return -EINVAL;
+ if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
+ (rt_policy(policy) != (attr->sched_priority != 0)))
+ return -EINVAL;
+
+ /*
+ * Allow unprivileged RT tasks to decrease priority:
+ */
+ if (user && !capable(CAP_SYS_NICE)) {
+ if (fair_policy(policy)) {
+ if (attr->sched_nice < task_nice(p) &&
+ !can_nice(p, attr->sched_nice))
+ return -EPERM;
+ }
+
+ if (rt_policy(policy)) {
+ unsigned long rlim_rtprio =
+ task_rlimit(p, RLIMIT_RTPRIO);
+
+ /* Can't set/change the rt policy: */
+ if (policy != p->policy && !rlim_rtprio)
+ return -EPERM;
+
+ /* Can't increase priority: */
+ if (attr->sched_priority > p->rt_priority &&
+ attr->sched_priority > rlim_rtprio)
+ return -EPERM;
+ }
+
+ /*
+ * Can't set/change SCHED_DEADLINE policy at all for now
+ * (safest behavior); in the future we would like to allow
+ * unprivileged DL tasks to increase their relative deadline
+ * or reduce their runtime (both ways reducing utilization)
+ */
+ if (dl_policy(policy))
+ return -EPERM;
+
+ /*
+ * Treat SCHED_IDLE as nice 20. Only allow a switch to
+ * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
+ */
+ if (task_has_idle_policy(p) && !idle_policy(policy)) {
+ if (!can_nice(p, task_nice(p)))
+ return -EPERM;
+ }
+
+ /* Can't change other user's priorities: */
+ if (!check_same_owner(p))
+ return -EPERM;
+
+ /* Normal users shall not reset the sched_reset_on_fork flag: */
+ if (p->sched_reset_on_fork && !reset_on_fork)
+ return -EPERM;
+ }
+
+ if (user) {
+ if (attr->sched_flags & SCHED_FLAG_SUGOV)
+ return -EINVAL;
+
+ retval = security_task_setscheduler(p);
+ if (retval)
+ return retval;
+ }
+
+ /* Update task specific "requested" clamps */
+ if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) {
+ retval = uclamp_validate(p, attr);
+ if (retval)
+ return retval;
+ }
+
+ /*
+ * SCHED_DEADLINE bandwidth accounting relies on stable cpusets
+ * information.
+ */
+ if (dl_policy(policy) || dl_policy(p->policy)) {
+ cpuset_locked = true;
+ cpuset_lock();
+ }
+
+ /*
+ * Make sure no PI-waiters arrive (or leave) while we are
+ * changing the priority of the task:
+ *
+ * To be able to change p->policy safely, the appropriate
+ * runqueue lock must be held.
+ */
+ rq = task_rq_lock(p, &rf);
+ update_rq_clock(rq);
+
+ /*
+ * Changing the policy of the stop threads its a very bad idea:
+ */
+ if (p == rq->stop) {
+ retval = -EINVAL;
+ goto unlock;
+ }
+
+ /*
+ * If not changing anything there's no need to proceed further,
+ * but store a possible modification of reset_on_fork.
+ */
+ if (unlikely(policy == p->policy)) {
+ if (fair_policy(policy) && attr->sched_nice != task_nice(p))
+ goto change;
+ if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
+ goto change;
+ if (dl_policy(policy) && dl_param_changed(p, attr))
+ goto change;
+ if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
+ goto change;
+
+ p->sched_reset_on_fork = reset_on_fork;
+ retval = 0;
+ goto unlock;
+ }
+change:
+
+ if (user) {
+#ifdef CONFIG_RT_GROUP_SCHED
+ /*
+ * Do not allow realtime tasks into groups that have no runtime
+ * assigned.
+ */
+ if (rt_bandwidth_enabled() && rt_policy(policy) &&
+ task_group(p)->rt_bandwidth.rt_runtime == 0 &&
+ !task_group_is_autogroup(task_group(p))) {
+ retval = -EPERM;
+ goto unlock;
+ }
+#endif
+#ifdef CONFIG_SMP
+ if (dl_bandwidth_enabled() && dl_policy(policy) &&
+ !(attr->sched_flags & SCHED_FLAG_SUGOV)) {
+ cpumask_t *span = rq->rd->span;
+
+ /*
+ * Don't allow tasks with an affinity mask smaller than
+ * the entire root_domain to become SCHED_DEADLINE. We
+ * will also fail if there's no bandwidth available.
+ */
+ if (!cpumask_subset(span, p->cpus_ptr) ||
+ rq->rd->dl_bw.bw == 0) {
+ retval = -EPERM;
+ goto unlock;
+ }
+ }
+#endif
+ }
+
+ /* Re-check policy now with rq lock held: */
+ if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
+ policy = oldpolicy = -1;
+ task_rq_unlock(rq, p, &rf);
+ if (cpuset_locked)
+ cpuset_unlock();
+ goto recheck;
+ }
+
+ /*
+ * If setscheduling to SCHED_DEADLINE (or changing the parameters
+ * of a SCHED_DEADLINE task) we need to check if enough bandwidth
+ * is available.
+ */
+ if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
+ retval = -EBUSY;
+ goto unlock;
+ }
+
+ p->sched_reset_on_fork = reset_on_fork;
+ oldprio = p->prio;
+
+ newprio = __normal_prio(policy, attr->sched_priority, attr->sched_nice);
+ if (pi) {
+ /*
+ * Take priority boosted tasks into account. If the new
+ * effective priority is unchanged, we just store the new
+ * normal parameters and do not touch the scheduler class and
+ * the runqueue. This will be done when the task deboost
+ * itself.
+ */
+ newprio = rt_effective_prio(p, newprio);
+ if (newprio == oldprio)
+ queue_flags &= ~DEQUEUE_MOVE;
+ }
+
+ queued = task_on_rq_queued(p);
+ running = task_current(rq, p);
+ if (queued)
+ dequeue_task(rq, p, queue_flags);
+ if (running)
+ put_prev_task(rq, p);
+
+ prev_class = p->sched_class;
+
+ if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
+ __setscheduler_params(p, attr);
+ __setscheduler_prio(p, newprio);
+ }
+ __setscheduler_uclamp(p, attr);
+
+ if (queued) {
+ /*
+ * We enqueue to tail when the priority of a task is
+ * increased (user space view).
+ */
+ if (oldprio < p->prio)
+ queue_flags |= ENQUEUE_HEAD;
+
+ enqueue_task(rq, p, queue_flags);
+ }
+ if (running)
+ set_next_task(rq, p);
+
+ check_class_changed(rq, p, prev_class, oldprio);
+
+ /* Avoid rq from going away on us: */
+ preempt_disable();
+ task_rq_unlock(rq, p, &rf);
+
+ if (pi) {
+ if (cpuset_locked)
+ cpuset_unlock();
+ rt_mutex_adjust_pi(p);
+ }
+
+ /* Run balance callbacks after we've adjusted the PI chain: */
+ balance_callback(rq);
+ preempt_enable();
+
+ return 0;
+
+unlock:
+ task_rq_unlock(rq, p, &rf);
+ if (cpuset_locked)
+ cpuset_unlock();
+ return retval;
+}
+
+static int _sched_setscheduler(struct task_struct *p, int policy,
+ const struct sched_param *param, bool check)
+{
+ struct sched_attr attr = {
+ .sched_policy = policy,
+ .sched_priority = param->sched_priority,
+ .sched_nice = PRIO_TO_NICE(p->static_prio),
+ };
+
+ /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
+ if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
+ attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
+ policy &= ~SCHED_RESET_ON_FORK;
+ attr.sched_policy = policy;
+ }
+
+ return __sched_setscheduler(p, &attr, check, true);
+}
+/**
+ * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
+ * @p: the task in question.
+ * @policy: new policy.
+ * @param: structure containing the new RT priority.
+ *
+ * Use sched_set_fifo(), read its comment.
+ *
+ * Return: 0 on success. An error code otherwise.
+ *
+ * NOTE that the task may be already dead.
+ */
+int sched_setscheduler(struct task_struct *p, int policy,
+ const struct sched_param *param)
+{
+ return _sched_setscheduler(p, policy, param, true);
+}
+
+int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
+{
+ return __sched_setscheduler(p, attr, true, true);
+}
+
+int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
+{
+ return __sched_setscheduler(p, attr, false, true);
+}
+
+/**
+ * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
+ * @p: the task in question.
+ * @policy: new policy.
+ * @param: structure containing the new RT priority.
+ *
+ * Just like sched_setscheduler, only don't bother checking if the
+ * current context has permission. For example, this is needed in
+ * stop_machine(): we create temporary high priority worker threads,
+ * but our caller might not have that capability.
+ *
+ * Return: 0 on success. An error code otherwise.
+ */
+int sched_setscheduler_nocheck(struct task_struct *p, int policy,
+ const struct sched_param *param)
+{
+ return _sched_setscheduler(p, policy, param, false);
+}
+
+/*
+ * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally
+ * incapable of resource management, which is the one thing an OS really should
+ * be doing.
+ *
+ * This is of course the reason it is limited to privileged users only.
+ *
+ * Worse still; it is fundamentally impossible to compose static priority
+ * workloads. You cannot take two correctly working static prio workloads
+ * and smash them together and still expect them to work.
+ *
+ * For this reason 'all' FIFO tasks the kernel creates are basically at:
+ *
+ * MAX_RT_PRIO / 2
+ *
+ * The administrator _MUST_ configure the system, the kernel simply doesn't
+ * know enough information to make a sensible choice.
+ */
+void sched_set_fifo(struct task_struct *p)
+{
+ struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 };
+ WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
+}
+EXPORT_SYMBOL_GPL(sched_set_fifo);
+
+/*
+ * For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
+ */
+void sched_set_fifo_low(struct task_struct *p)
+{
+ struct sched_param sp = { .sched_priority = 1 };
+ WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
+}
+EXPORT_SYMBOL_GPL(sched_set_fifo_low);
+
+void sched_set_normal(struct task_struct *p, int nice)
+{
+ struct sched_attr attr = {
+ .sched_policy = SCHED_NORMAL,
+ .sched_nice = nice,
+ };
+ WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0);
+}
+EXPORT_SYMBOL_GPL(sched_set_normal);
+
+static int
+do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
+{
+ struct sched_param lparam;
+ struct task_struct *p;
+ int retval;
+
+ if (!param || pid < 0)
+ return -EINVAL;
+ if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
+ return -EFAULT;
+
+ rcu_read_lock();
+ retval = -ESRCH;
+ p = find_process_by_pid(pid);
+ if (likely(p))
+ get_task_struct(p);
+ rcu_read_unlock();
+
+ if (likely(p)) {
+ retval = sched_setscheduler(p, policy, &lparam);
+ put_task_struct(p);
+ }
+
+ return retval;
+}
+
+/*
+ * Mimics kernel/events/core.c perf_copy_attr().
+ */
+static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
+{
+ u32 size;
+ int ret;
+
+ /* Zero the full structure, so that a short copy will be nice: */
+ memset(attr, 0, sizeof(*attr));
+
+ ret = get_user(size, &uattr->size);
+ if (ret)
+ return ret;
+
+ /* ABI compatibility quirk: */
+ if (!size)
+ size = SCHED_ATTR_SIZE_VER0;
+ if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)
+ goto err_size;
+
+ ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
+ if (ret) {
+ if (ret == -E2BIG)
+ goto err_size;
+ return ret;
+ }
+
+ if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) &&
+ size < SCHED_ATTR_SIZE_VER1)
+ return -EINVAL;
+
+ /*
+ * XXX: Do we want to be lenient like existing syscalls; or do we want
+ * to be strict and return an error on out-of-bounds values?
+ */
+ attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
+
+ return 0;
+
+err_size:
+ put_user(sizeof(*attr), &uattr->size);
+ return -E2BIG;
+}
+
+/**
+ * sys_sched_setscheduler - set/change the scheduler policy and RT priority
+ * @pid: the pid in question.
+ * @policy: new policy.
+ * @param: structure containing the new RT priority.
+ *
+ * Return: 0 on success. An error code otherwise.
+ */
+SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
+{
+ if (policy < 0)
+ return -EINVAL;
+
+ return do_sched_setscheduler(pid, policy, param);
+}
+
+/**
+ * sys_sched_setparam - set/change the RT priority of a thread
+ * @pid: the pid in question.
+ * @param: structure containing the new RT priority.
+ *
+ * Return: 0 on success. An error code otherwise.
+ */
+SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
+{
+ return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
+}
+
+/**
+ * sys_sched_setattr - same as above, but with extended sched_attr
+ * @pid: the pid in question.
+ * @uattr: structure containing the extended parameters.
+ * @flags: for future extension.
+ */
+SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
+ unsigned int, flags)
+{
+ struct sched_attr attr;
+ struct task_struct *p;
+ int retval;
+
+ if (!uattr || pid < 0 || flags)
+ return -EINVAL;
+
+ retval = sched_copy_attr(uattr, &attr);
+ if (retval)
+ return retval;
+
+ if ((int)attr.sched_policy < 0)
+ return -EINVAL;
+ if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
+ attr.sched_policy = SETPARAM_POLICY;
+
+ rcu_read_lock();
+ retval = -ESRCH;
+ p = find_process_by_pid(pid);
+ if (likely(p))
+ get_task_struct(p);
+ rcu_read_unlock();
+
+ if (likely(p)) {
+ retval = sched_setattr(p, &attr);
+ put_task_struct(p);
+ }
+
+ return retval;
+}
+
+/**
+ * sys_sched_getscheduler - get the policy (scheduling class) of a thread
+ * @pid: the pid in question.
+ *
+ * Return: On success, the policy of the thread. Otherwise, a negative error
+ * code.
+ */
+SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
+{
+ struct task_struct *p;
+ int retval;
+
+ if (pid < 0)
+ return -EINVAL;
+
+ retval = -ESRCH;
+ rcu_read_lock();
+ p = find_process_by_pid(pid);
+ if (p) {
+ retval = security_task_getscheduler(p);
+ if (!retval)
+ retval = p->policy
+ | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
+ }
+ rcu_read_unlock();
+ return retval;
+}
+
+/**
+ * sys_sched_getparam - get the RT priority of a thread
+ * @pid: the pid in question.
+ * @param: structure containing the RT priority.
+ *
+ * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
+ * code.
+ */
+SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
+{
+ struct sched_param lp = { .sched_priority = 0 };
+ struct task_struct *p;
+ int retval;
+
+ if (!param || pid < 0)
+ return -EINVAL;
+
+ rcu_read_lock();
+ p = find_process_by_pid(pid);
+ retval = -ESRCH;
+ if (!p)
+ goto out_unlock;
+
+ retval = security_task_getscheduler(p);
+ if (retval)
+ goto out_unlock;
+
+ if (task_has_rt_policy(p))
+ lp.sched_priority = p->rt_priority;
+ rcu_read_unlock();
+
+ /*
+ * This one might sleep, we cannot do it with a spinlock held ...
+ */
+ retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
+
+ return retval;
+
+out_unlock:
+ rcu_read_unlock();
+ return retval;
+}
+
+/*
+ * Copy the kernel size attribute structure (which might be larger
+ * than what user-space knows about) to user-space.
+ *
+ * Note that all cases are valid: user-space buffer can be larger or
+ * smaller than the kernel-space buffer. The usual case is that both
+ * have the same size.
+ */
+static int
+sched_attr_copy_to_user(struct sched_attr __user *uattr,
+ struct sched_attr *kattr,
+ unsigned int usize)
+{
+ unsigned int ksize = sizeof(*kattr);
+
+ if (!access_ok(uattr, usize))
+ return -EFAULT;
+
+ /*
+ * sched_getattr() ABI forwards and backwards compatibility:
+ *
+ * If usize == ksize then we just copy everything to user-space and all is good.
+ *
+ * If usize < ksize then we only copy as much as user-space has space for,
+ * this keeps ABI compatibility as well. We skip the rest.
+ *
+ * If usize > ksize then user-space is using a newer version of the ABI,
+ * which part the kernel doesn't know about. Just ignore it - tooling can
+ * detect the kernel's knowledge of attributes from the attr->size value
+ * which is set to ksize in this case.
+ */
+ kattr->size = min(usize, ksize);
+
+ if (copy_to_user(uattr, kattr, kattr->size))
+ return -EFAULT;
+
+ return 0;
+}
+
+/**
+ * sys_sched_getattr - similar to sched_getparam, but with sched_attr
+ * @pid: the pid in question.
+ * @uattr: structure containing the extended parameters.
+ * @usize: sizeof(attr) for fwd/bwd comp.
+ * @flags: for future extension.
+ */
+SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
+ unsigned int, usize, unsigned int, flags)
+{
+ struct sched_attr kattr = { };
+ struct task_struct *p;
+ int retval;
+
+ if (!uattr || pid < 0 || usize > PAGE_SIZE ||
+ usize < SCHED_ATTR_SIZE_VER0 || flags)
+ return -EINVAL;
+
+ rcu_read_lock();
+ p = find_process_by_pid(pid);
+ retval = -ESRCH;
+ if (!p)
+ goto out_unlock;
+
+ retval = security_task_getscheduler(p);
+ if (retval)
+ goto out_unlock;
+
+ kattr.sched_policy = p->policy;
+ if (p->sched_reset_on_fork)
+ kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
+ if (task_has_dl_policy(p))
+ __getparam_dl(p, &kattr);
+ else if (task_has_rt_policy(p))
+ kattr.sched_priority = p->rt_priority;
+ else
+ kattr.sched_nice = task_nice(p);
+
+#ifdef CONFIG_UCLAMP_TASK
+ /*
+ * This could race with another potential updater, but this is fine
+ * because it'll correctly read the old or the new value. We don't need
+ * to guarantee who wins the race as long as it doesn't return garbage.
+ */
+ kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
+ kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
+#endif
+
+ rcu_read_unlock();
+
+ return sched_attr_copy_to_user(uattr, &kattr, usize);
+
+out_unlock:
+ rcu_read_unlock();
+ return retval;
+}
+
+long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
+{
+ cpumask_var_t cpus_allowed, new_mask;
+ struct task_struct *p;
+ int retval;
+
+ rcu_read_lock();
+
+ p = find_process_by_pid(pid);
+ if (!p) {
+ rcu_read_unlock();
+ return -ESRCH;
+ }
+
+ /* Prevent p going away */
+ get_task_struct(p);
+ rcu_read_unlock();
+
+ if (p->flags & PF_NO_SETAFFINITY) {
+ retval = -EINVAL;
+ goto out_put_task;
+ }
+ if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
+ retval = -ENOMEM;
+ goto out_put_task;
+ }
+ if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
+ retval = -ENOMEM;
+ goto out_free_cpus_allowed;
+ }
+ retval = -EPERM;
+ if (!check_same_owner(p)) {
+ rcu_read_lock();
+ if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
+ rcu_read_unlock();
+ goto out_free_new_mask;
+ }
+ rcu_read_unlock();
+ }
+
+ retval = security_task_setscheduler(p);
+ if (retval)
+ goto out_free_new_mask;
+
+
+ cpuset_cpus_allowed(p, cpus_allowed);
+ cpumask_and(new_mask, in_mask, cpus_allowed);
+
+ /*
+ * Since bandwidth control happens on root_domain basis,
+ * if admission test is enabled, we only admit -deadline
+ * tasks allowed to run on all the CPUs in the task's
+ * root_domain.
+ */
+#ifdef CONFIG_SMP
+ if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
+ rcu_read_lock();
+ if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
+ retval = -EBUSY;
+ rcu_read_unlock();
+ goto out_free_new_mask;
+ }
+ rcu_read_unlock();
+ }
+#endif
+again:
+ retval = __set_cpus_allowed_ptr(p, new_mask, true);
+
+ if (!retval) {
+ cpuset_cpus_allowed(p, cpus_allowed);
+ if (!cpumask_subset(new_mask, cpus_allowed)) {
+ /*
+ * We must have raced with a concurrent cpuset
+ * update. Just reset the cpus_allowed to the
+ * cpuset's cpus_allowed
+ */
+ cpumask_copy(new_mask, cpus_allowed);
+ goto again;
+ }
+ }
+out_free_new_mask:
+ free_cpumask_var(new_mask);
+out_free_cpus_allowed:
+ free_cpumask_var(cpus_allowed);
+out_put_task:
+ put_task_struct(p);
+ return retval;
+}
+
+static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
+ struct cpumask *new_mask)
+{
+ if (len < cpumask_size())
+ cpumask_clear(new_mask);
+ else if (len > cpumask_size())
+ len = cpumask_size();
+
+ return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
+}
+
+/**
+ * sys_sched_setaffinity - set the CPU affinity of a process
+ * @pid: pid of the process
+ * @len: length in bytes of the bitmask pointed to by user_mask_ptr
+ * @user_mask_ptr: user-space pointer to the new CPU mask
+ *
+ * Return: 0 on success. An error code otherwise.
+ */
+SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
+ unsigned long __user *, user_mask_ptr)
+{
+ cpumask_var_t new_mask;
+ int retval;
+
+ if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
+ return -ENOMEM;
+
+ retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
+ if (retval == 0)
+ retval = sched_setaffinity(pid, new_mask);
+ free_cpumask_var(new_mask);
+ return retval;
+}
+
+long sched_getaffinity(pid_t pid, struct cpumask *mask)
+{
+ struct task_struct *p;
+ unsigned long flags;
+ int retval;
+
+ rcu_read_lock();
+
+ retval = -ESRCH;
+ p = find_process_by_pid(pid);
+ if (!p)
+ goto out_unlock;
+
+ retval = security_task_getscheduler(p);
+ if (retval)
+ goto out_unlock;
+
+ raw_spin_lock_irqsave(&p->pi_lock, flags);
+ cpumask_and(mask, &p->cpus_mask, cpu_active_mask);
+ raw_spin_unlock_irqrestore(&p->pi_lock, flags);
+
+out_unlock:
+ rcu_read_unlock();
+
+ return retval;
+}
+
+/**
+ * sys_sched_getaffinity - get the CPU affinity of a process
+ * @pid: pid of the process
+ * @len: length in bytes of the bitmask pointed to by user_mask_ptr
+ * @user_mask_ptr: user-space pointer to hold the current CPU mask
+ *
+ * Return: size of CPU mask copied to user_mask_ptr on success. An
+ * error code otherwise.
+ */
+SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
+ unsigned long __user *, user_mask_ptr)
+{
+ int ret;
+ cpumask_var_t mask;
+
+ if ((len * BITS_PER_BYTE) < nr_cpu_ids)
+ return -EINVAL;
+ if (len & (sizeof(unsigned long)-1))
+ return -EINVAL;
+
+ if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
+ return -ENOMEM;
+
+ ret = sched_getaffinity(pid, mask);
+ if (ret == 0) {
+ unsigned int retlen = min(len, cpumask_size());
+
+ if (copy_to_user(user_mask_ptr, cpumask_bits(mask), retlen))
+ ret = -EFAULT;
+ else
+ ret = retlen;
+ }
+ free_cpumask_var(mask);
+
+ return ret;
+}
+
+/**
+ * sys_sched_yield - yield the current processor to other threads.
+ *
+ * This function yields the current CPU to other tasks. If there are no
+ * other threads running on this CPU then this function will return.
+ *
+ * Return: 0.
+ */
+static void do_sched_yield(void)
+{
+ struct rq_flags rf;
+ struct rq *rq;
+
+ rq = this_rq_lock_irq(&rf);
+
+ schedstat_inc(rq->yld_count);
+ current->sched_class->yield_task(rq);
+
+ preempt_disable();
+ rq_unlock_irq(rq, &rf);
+ sched_preempt_enable_no_resched();
+
+ schedule();
+}
+
+SYSCALL_DEFINE0(sched_yield)
+{
+ do_sched_yield();
+ return 0;
+}
+
+#ifndef CONFIG_PREEMPTION
+int __sched _cond_resched(void)
+{
+ if (should_resched(0)) {
+ preempt_schedule_common();
+ return 1;
+ }
+ rcu_all_qs();
+ return 0;
+}
+EXPORT_SYMBOL(_cond_resched);
+#endif
+
+/*
+ * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
+ * call schedule, and on return reacquire the lock.
+ *
+ * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
+ * operations here to prevent schedule() from being called twice (once via
+ * spin_unlock(), once by hand).
+ */
+int __cond_resched_lock(spinlock_t *lock)
+{
+ int resched = should_resched(PREEMPT_LOCK_OFFSET);
+ int ret = 0;
+
+ lockdep_assert_held(lock);
+
+ if (spin_needbreak(lock) || resched) {
+ spin_unlock(lock);
+ if (resched)
+ preempt_schedule_common();
+ else
+ cpu_relax();
+ ret = 1;
+ spin_lock(lock);
+ }
+ return ret;
+}
+EXPORT_SYMBOL(__cond_resched_lock);
+
+/**
+ * yield - yield the current processor to other threads.
+ *
+ * Do not ever use this function, there's a 99% chance you're doing it wrong.
+ *
+ * The scheduler is at all times free to pick the calling task as the most
+ * eligible task to run, if removing the yield() call from your code breaks
+ * it, its already broken.
+ *
+ * Typical broken usage is:
+ *
+ * while (!event)
+ * yield();
+ *
+ * where one assumes that yield() will let 'the other' process run that will
+ * make event true. If the current task is a SCHED_FIFO task that will never
+ * happen. Never use yield() as a progress guarantee!!
+ *
+ * If you want to use yield() to wait for something, use wait_event().
+ * If you want to use yield() to be 'nice' for others, use cond_resched().
+ * If you still want to use yield(), do not!
+ */
+void __sched yield(void)
+{
+ set_current_state(TASK_RUNNING);
+ do_sched_yield();
+}
+EXPORT_SYMBOL(yield);
+
+/**
+ * yield_to - yield the current processor to another thread in
+ * your thread group, or accelerate that thread toward the
+ * processor it's on.
+ * @p: target task
+ * @preempt: whether task preemption is allowed or not
+ *
+ * It's the caller's job to ensure that the target task struct
+ * can't go away on us before we can do any checks.
+ *
+ * Return:
+ * true (>0) if we indeed boosted the target task.
+ * false (0) if we failed to boost the target.
+ * -ESRCH if there's no task to yield to.
+ */
+int __sched yield_to(struct task_struct *p, bool preempt)
+{
+ struct task_struct *curr = current;
+ struct rq *rq, *p_rq;
+ unsigned long flags;
+ int yielded = 0;
+
+ local_irq_save(flags);
+ rq = this_rq();
+
+again:
+ p_rq = task_rq(p);
+ /*
+ * If we're the only runnable task on the rq and target rq also
+ * has only one task, there's absolutely no point in yielding.
+ */
+ if (rq->nr_running == 1 && p_rq->nr_running == 1) {
+ yielded = -ESRCH;
+ goto out_irq;
+ }
+
+ double_rq_lock(rq, p_rq);
+ if (task_rq(p) != p_rq) {
+ double_rq_unlock(rq, p_rq);
+ goto again;
+ }
+
+ if (!curr->sched_class->yield_to_task)
+ goto out_unlock;
+
+ if (curr->sched_class != p->sched_class)
+ goto out_unlock;
+
+ if (task_running(p_rq, p) || p->state)
+ goto out_unlock;
+
+ yielded = curr->sched_class->yield_to_task(rq, p);
+ if (yielded) {
+ schedstat_inc(rq->yld_count);
+ /*
+ * Make p's CPU reschedule; pick_next_entity takes care of
+ * fairness.
+ */
+ if (preempt && rq != p_rq)
+ resched_curr(p_rq);
+ }
+
+out_unlock:
+ double_rq_unlock(rq, p_rq);
+out_irq:
+ local_irq_restore(flags);
+
+ if (yielded > 0)
+ schedule();
+
+ return yielded;
+}
+EXPORT_SYMBOL_GPL(yield_to);
+
+int io_schedule_prepare(void)
+{
+ int old_iowait = current->in_iowait;
+
+ current->in_iowait = 1;
+ blk_schedule_flush_plug(current);
+
+ return old_iowait;
+}
+
+void io_schedule_finish(int token)
+{
+ current->in_iowait = token;
+}
+
+/*
+ * This task is about to go to sleep on IO. Increment rq->nr_iowait so
+ * that process accounting knows that this is a task in IO wait state.
+ */
+long __sched io_schedule_timeout(long timeout)
+{
+ int token;
+ long ret;
+
+ token = io_schedule_prepare();
+ ret = schedule_timeout(timeout);
+ io_schedule_finish(token);
+
+ return ret;
+}
+EXPORT_SYMBOL(io_schedule_timeout);
+
+void __sched io_schedule(void)
+{
+ int token;
+
+ token = io_schedule_prepare();
+ schedule();
+ io_schedule_finish(token);
+}
+EXPORT_SYMBOL(io_schedule);
+
+/**
+ * sys_sched_get_priority_max - return maximum RT priority.
+ * @policy: scheduling class.
+ *
+ * Return: On success, this syscall returns the maximum
+ * rt_priority that can be used by a given scheduling class.
+ * On failure, a negative error code is returned.
+ */
+SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
+{
+ int ret = -EINVAL;
+
+ switch (policy) {
+ case SCHED_FIFO:
+ case SCHED_RR:
+ ret = MAX_USER_RT_PRIO-1;
+ break;
+ case SCHED_DEADLINE:
+ case SCHED_NORMAL:
+ case SCHED_BATCH:
+ case SCHED_IDLE:
+ ret = 0;
+ break;
+ }
+ return ret;
+}
+
+/**
+ * sys_sched_get_priority_min - return minimum RT priority.
+ * @policy: scheduling class.
+ *
+ * Return: On success, this syscall returns the minimum
+ * rt_priority that can be used by a given scheduling class.
+ * On failure, a negative error code is returned.
+ */
+SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
+{
+ int ret = -EINVAL;
+
+ switch (policy) {
+ case SCHED_FIFO:
+ case SCHED_RR:
+ ret = 1;
+ break;
+ case SCHED_DEADLINE:
+ case SCHED_NORMAL:
+ case SCHED_BATCH:
+ case SCHED_IDLE:
+ ret = 0;
+ }
+ return ret;
+}
+
+static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
+{
+ struct task_struct *p;
+ unsigned int time_slice;
+ struct rq_flags rf;
+ struct rq *rq;
+ int retval;
+
+ if (pid < 0)
+ return -EINVAL;
+
+ retval = -ESRCH;
+ rcu_read_lock();
+ p = find_process_by_pid(pid);
+ if (!p)
+ goto out_unlock;
+
+ retval = security_task_getscheduler(p);
+ if (retval)
+ goto out_unlock;
+
+ rq = task_rq_lock(p, &rf);
+ time_slice = 0;
+ if (p->sched_class->get_rr_interval)
+ time_slice = p->sched_class->get_rr_interval(rq, p);
+ task_rq_unlock(rq, p, &rf);
+
+ rcu_read_unlock();
+ jiffies_to_timespec64(time_slice, t);
+ return 0;
+
+out_unlock:
+ rcu_read_unlock();
+ return retval;
+}
+
+/**
+ * sys_sched_rr_get_interval - return the default timeslice of a process.
+ * @pid: pid of the process.
+ * @interval: userspace pointer to the timeslice value.
+ *
+ * this syscall writes the default timeslice value of a given process
+ * into the user-space timespec buffer. A value of '0' means infinity.
+ *
+ * Return: On success, 0 and the timeslice is in @interval. Otherwise,
+ * an error code.
+ */
+SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
+ struct __kernel_timespec __user *, interval)
+{
+ struct timespec64 t;
+ int retval = sched_rr_get_interval(pid, &t);
+
+ if (retval == 0)
+ retval = put_timespec64(&t, interval);
+
+ return retval;
+}
+
+#ifdef CONFIG_COMPAT_32BIT_TIME
+SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid,
+ struct old_timespec32 __user *, interval)
+{
+ struct timespec64 t;
+ int retval = sched_rr_get_interval(pid, &t);
+
+ if (retval == 0)
+ retval = put_old_timespec32(&t, interval);
+ return retval;
+}
+#endif
+
+void sched_show_task(struct task_struct *p)
+{
+ unsigned long free = 0;
+ int ppid;
+
+ if (!try_get_task_stack(p))
+ return;
+
+ pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p));
+
+ if (p->state == TASK_RUNNING)
+ pr_cont(" running task ");
+#ifdef CONFIG_DEBUG_STACK_USAGE
+ free = stack_not_used(p);
+#endif
+ ppid = 0;
+ rcu_read_lock();
+ if (pid_alive(p))
+ ppid = task_pid_nr(rcu_dereference(p->real_parent));
+ rcu_read_unlock();
+ pr_cont(" stack:%5lu pid:%5d ppid:%6d flags:0x%08lx\n",
+ free, task_pid_nr(p), ppid,
+ (unsigned long)task_thread_info(p)->flags);
+
+ print_worker_info(KERN_INFO, p);
+ show_stack(p, NULL, KERN_INFO);
+ put_task_stack(p);
+}
+EXPORT_SYMBOL_GPL(sched_show_task);
+
+static inline bool
+state_filter_match(unsigned long state_filter, struct task_struct *p)
+{
+ /* no filter, everything matches */
+ if (!state_filter)
+ return true;
+
+ /* filter, but doesn't match */
+ if (!(p->state & state_filter))
+ return false;
+
+ /*
+ * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
+ * TASK_KILLABLE).
+ */
+ if (state_filter == TASK_UNINTERRUPTIBLE && p->state == TASK_IDLE)
+ return false;
+
+ return true;
+}
+
+
+void show_state_filter(unsigned long state_filter)
+{
+ struct task_struct *g, *p;
+
+ rcu_read_lock();
+ for_each_process_thread(g, p) {
+ /*
+ * reset the NMI-timeout, listing all files on a slow
+ * console might take a lot of time:
+ * Also, reset softlockup watchdogs on all CPUs, because
+ * another CPU might be blocked waiting for us to process
+ * an IPI.
+ */
+ touch_nmi_watchdog();
+ touch_all_softlockup_watchdogs();
+ if (state_filter_match(state_filter, p))
+ sched_show_task(p);
+ }
+
+#ifdef CONFIG_SCHED_DEBUG
+ if (!state_filter)
+ sysrq_sched_debug_show();
+#endif
+ rcu_read_unlock();
+ /*
+ * Only show locks if all tasks are dumped:
+ */
+ if (!state_filter)
+ debug_show_all_locks();
+}
+
+/**
+ * init_idle - set up an idle thread for a given CPU
+ * @idle: task in question
+ * @cpu: CPU the idle task belongs to
+ *
+ * NOTE: this function does not set the idle thread's NEED_RESCHED
+ * flag, to make booting more robust.
+ */
+void __init init_idle(struct task_struct *idle, int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ unsigned long flags;
+
+ __sched_fork(0, idle);
+
+ raw_spin_lock_irqsave(&idle->pi_lock, flags);
+ raw_spin_lock(&rq->lock);
+
+ idle->state = TASK_RUNNING;
+ idle->se.exec_start = sched_clock();
+ idle->flags |= PF_IDLE;
+
+#ifdef CONFIG_SMP
+ /*
+ * Its possible that init_idle() gets called multiple times on a task,
+ * in that case do_set_cpus_allowed() will not do the right thing.
+ *
+ * And since this is boot we can forgo the serialization.
+ */
+ set_cpus_allowed_common(idle, cpumask_of(cpu));
+#endif
+ /*
+ * We're having a chicken and egg problem, even though we are
+ * holding rq->lock, the CPU isn't yet set to this CPU so the
+ * lockdep check in task_group() will fail.
+ *
+ * Similar case to sched_fork(). / Alternatively we could
+ * use task_rq_lock() here and obtain the other rq->lock.
+ *
+ * Silence PROVE_RCU
+ */
+ rcu_read_lock();
+ __set_task_cpu(idle, cpu);
+ rcu_read_unlock();
+
+ rq->idle = idle;
+ rcu_assign_pointer(rq->curr, idle);
+ idle->on_rq = TASK_ON_RQ_QUEUED;
+#ifdef CONFIG_SMP
+ idle->on_cpu = 1;
+#endif
+ raw_spin_unlock(&rq->lock);
+ raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
+
+ /* Set the preempt count _outside_ the spinlocks! */
+ init_idle_preempt_count(idle, cpu);
+
+ /*
+ * The idle tasks have their own, simple scheduling class:
+ */
+ idle->sched_class = &idle_sched_class;
+ ftrace_graph_init_idle_task(idle, cpu);
+ vtime_init_idle(idle, cpu);
+#ifdef CONFIG_SMP
+ sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
+#endif
+}
+
+#ifdef CONFIG_SMP
+
+int cpuset_cpumask_can_shrink(const struct cpumask *cur,
+ const struct cpumask *trial)
+{
+ int ret = 1;
+
+ if (!cpumask_weight(cur))
+ return ret;
+
+ ret = dl_cpuset_cpumask_can_shrink(cur, trial);
+
+ return ret;
+}
+
+int task_can_attach(struct task_struct *p)
+{
+ int ret = 0;
+
+ /*
+ * Kthreads which disallow setaffinity shouldn't be moved
+ * to a new cpuset; we don't want to change their CPU
+ * affinity and isolating such threads by their set of
+ * allowed nodes is unnecessary. Thus, cpusets are not
+ * applicable for such threads. This prevents checking for
+ * success of set_cpus_allowed_ptr() on all attached tasks
+ * before cpus_mask may be changed.
+ */
+ if (p->flags & PF_NO_SETAFFINITY)
+ ret = -EINVAL;
+
+ return ret;
+}
+
+bool sched_smp_initialized __read_mostly;
+
+#ifdef CONFIG_NUMA_BALANCING
+/* Migrate current task p to target_cpu */
+int migrate_task_to(struct task_struct *p, int target_cpu)
+{
+ struct migration_arg arg = { p, target_cpu };
+ int curr_cpu = task_cpu(p);
+
+ if (curr_cpu == target_cpu)
+ return 0;
+
+ if (!cpumask_test_cpu(target_cpu, p->cpus_ptr))
+ return -EINVAL;
+
+ /* TODO: This is not properly updating schedstats */
+
+ trace_sched_move_numa(p, curr_cpu, target_cpu);
+ return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
+}
+
+/*
+ * Requeue a task on a given node and accurately track the number of NUMA
+ * tasks on the runqueues
+ */
+void sched_setnuma(struct task_struct *p, int nid)
+{
+ bool queued, running;
+ struct rq_flags rf;
+ struct rq *rq;
+
+ rq = task_rq_lock(p, &rf);
+ queued = task_on_rq_queued(p);
+ running = task_current(rq, p);
+
+ if (queued)
+ dequeue_task(rq, p, DEQUEUE_SAVE);
+ if (running)
+ put_prev_task(rq, p);
+
+ p->numa_preferred_nid = nid;
+
+ if (queued)
+ enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
+ if (running)
+ set_next_task(rq, p);
+ task_rq_unlock(rq, p, &rf);
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * Ensure that the idle task is using init_mm right before its CPU goes
+ * offline.
+ */
+void idle_task_exit(void)
+{
+ struct mm_struct *mm = current->active_mm;
+
+ BUG_ON(cpu_online(smp_processor_id()));
+ BUG_ON(current != this_rq()->idle);
+
+ if (mm != &init_mm) {
+ switch_mm(mm, &init_mm, current);
+ finish_arch_post_lock_switch();
+ }
+
+ /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
+}
+
+/*
+ * Since this CPU is going 'away' for a while, fold any nr_active delta
+ * we might have. Assumes we're called after migrate_tasks() so that the
+ * nr_active count is stable. We need to take the teardown thread which
+ * is calling this into account, so we hand in adjust = 1 to the load
+ * calculation.
+ *
+ * Also see the comment "Global load-average calculations".
+ */
+static void calc_load_migrate(struct rq *rq)
+{
+ long delta = calc_load_fold_active(rq, 1);
+ if (delta)
+ atomic_long_add(delta, &calc_load_tasks);
+}
+
+static struct task_struct *__pick_migrate_task(struct rq *rq)
+{
+ const struct sched_class *class;
+ struct task_struct *next;
+
+ for_each_class(class) {
+ next = class->pick_next_task(rq);
+ if (next) {
+ next->sched_class->put_prev_task(rq, next);
+ return next;
+ }
+ }
+
+ /* The idle class should always have a runnable task */
+ BUG();
+}
+
+/*
+ * Migrate all tasks from the rq, sleeping tasks will be migrated by
+ * try_to_wake_up()->select_task_rq().
+ *
+ * Called with rq->lock held even though we'er in stop_machine() and
+ * there's no concurrency possible, we hold the required locks anyway
+ * because of lock validation efforts.
+ */
+static void migrate_tasks(struct rq *dead_rq, struct rq_flags *rf)
+{
+ struct rq *rq = dead_rq;
+ struct task_struct *next, *stop = rq->stop;
+ struct rq_flags orf = *rf;
+ int dest_cpu;
+
+ /*
+ * Fudge the rq selection such that the below task selection loop
+ * doesn't get stuck on the currently eligible stop task.
+ *
+ * We're currently inside stop_machine() and the rq is either stuck
+ * in the stop_machine_cpu_stop() loop, or we're executing this code,
+ * either way we should never end up calling schedule() until we're
+ * done here.
+ */
+ rq->stop = NULL;
+
+ /*
+ * put_prev_task() and pick_next_task() sched
+ * class method both need to have an up-to-date
+ * value of rq->clock[_task]
+ */
+ update_rq_clock(rq);
+
+ for (;;) {
+ /*
+ * There's this thread running, bail when that's the only
+ * remaining thread:
+ */
+ if (rq->nr_running == 1)
+ break;
+
+ next = __pick_migrate_task(rq);
+
+ /*
+ * Rules for changing task_struct::cpus_mask are holding
+ * both pi_lock and rq->lock, such that holding either
+ * stabilizes the mask.
+ *
+ * Drop rq->lock is not quite as disastrous as it usually is
+ * because !cpu_active at this point, which means load-balance
+ * will not interfere. Also, stop-machine.
+ */
+ rq_unlock(rq, rf);
+ raw_spin_lock(&next->pi_lock);
+ rq_relock(rq, rf);
+
+ /*
+ * Since we're inside stop-machine, _nothing_ should have
+ * changed the task, WARN if weird stuff happened, because in
+ * that case the above rq->lock drop is a fail too.
+ */
+ if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) {
+ raw_spin_unlock(&next->pi_lock);
+ continue;
+ }
+
+ /* Find suitable destination for @next, with force if needed. */
+ dest_cpu = select_fallback_rq(dead_rq->cpu, next);
+ rq = __migrate_task(rq, rf, next, dest_cpu);
+ if (rq != dead_rq) {
+ rq_unlock(rq, rf);
+ rq = dead_rq;
+ *rf = orf;
+ rq_relock(rq, rf);
+ }
+ raw_spin_unlock(&next->pi_lock);
+ }
+
+ rq->stop = stop;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
+void set_rq_online(struct rq *rq)
+{
+ if (!rq->online) {
+ const struct sched_class *class;
+
+ cpumask_set_cpu(rq->cpu, rq->rd->online);
+ rq->online = 1;
+
+ for_each_class(class) {
+ if (class->rq_online)
+ class->rq_online(rq);
+ }
+ }
+}
+
+void set_rq_offline(struct rq *rq)
+{
+ if (rq->online) {
+ const struct sched_class *class;
+
+ for_each_class(class) {
+ if (class->rq_offline)
+ class->rq_offline(rq);
+ }
+
+ cpumask_clear_cpu(rq->cpu, rq->rd->online);
+ rq->online = 0;
+ }
+}
+
+/*
+ * used to mark begin/end of suspend/resume:
+ */
+static int num_cpus_frozen;
+
+/*
+ * Update cpusets according to cpu_active mask. If cpusets are
+ * disabled, cpuset_update_active_cpus() becomes a simple wrapper
+ * around partition_sched_domains().
+ *
+ * If we come here as part of a suspend/resume, don't touch cpusets because we
+ * want to restore it back to its original state upon resume anyway.
+ */
+static void cpuset_cpu_active(void)
+{
+ if (cpuhp_tasks_frozen) {
+ /*
+ * num_cpus_frozen tracks how many CPUs are involved in suspend
+ * resume sequence. As long as this is not the last online
+ * operation in the resume sequence, just build a single sched
+ * domain, ignoring cpusets.
+ */
+ partition_sched_domains(1, NULL, NULL);
+ if (--num_cpus_frozen)
+ return;
+ /*
+ * This is the last CPU online operation. So fall through and
+ * restore the original sched domains by considering the
+ * cpuset configurations.
+ */
+ cpuset_force_rebuild();
+ }
+ cpuset_update_active_cpus();
+}
+
+static int cpuset_cpu_inactive(unsigned int cpu)
+{
+ if (!cpuhp_tasks_frozen) {
+ int ret = dl_bw_check_overflow(cpu);
+
+ if (ret)
+ return ret;
+ cpuset_update_active_cpus();
+ } else {
+ num_cpus_frozen++;
+ partition_sched_domains(1, NULL, NULL);
+ }
+ return 0;
+}
+
+int sched_cpu_activate(unsigned int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ struct rq_flags rf;
+
+#ifdef CONFIG_SCHED_SMT
+ /*
+ * When going up, increment the number of cores with SMT present.
+ */
+ if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+ static_branch_inc_cpuslocked(&sched_smt_present);
+#endif
+ set_cpu_active(cpu, true);
+
+ if (sched_smp_initialized) {
+ sched_domains_numa_masks_set(cpu);
+ cpuset_cpu_active();
+ }
+
+ /*
+ * Put the rq online, if not already. This happens:
+ *
+ * 1) In the early boot process, because we build the real domains
+ * after all CPUs have been brought up.
+ *
+ * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
+ * domains.
+ */
+ rq_lock_irqsave(rq, &rf);
+ if (rq->rd) {
+ BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
+ set_rq_online(rq);
+ }
+ rq_unlock_irqrestore(rq, &rf);
+
+ return 0;
+}
+
+int sched_cpu_deactivate(unsigned int cpu)
+{
+ int ret;
+
+ set_cpu_active(cpu, false);
+ /*
+ * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
+ * users of this state to go away such that all new such users will
+ * observe it.
+ *
+ * Do sync before park smpboot threads to take care the rcu boost case.
+ */
+ synchronize_rcu();
+
+#ifdef CONFIG_SCHED_SMT
+ /*
+ * When going down, decrement the number of cores with SMT present.
+ */
+ if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
+ static_branch_dec_cpuslocked(&sched_smt_present);
+#endif
+
+ if (!sched_smp_initialized)
+ return 0;
+
+ ret = cpuset_cpu_inactive(cpu);
+ if (ret) {
+ set_cpu_active(cpu, true);
+ return ret;
+ }
+ sched_domains_numa_masks_clear(cpu);
+ return 0;
+}
+
+static void sched_rq_cpu_starting(unsigned int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ rq->calc_load_update = calc_load_update;
+ update_max_interval();
+}
+
+int sched_cpu_starting(unsigned int cpu)
+{
+ sched_rq_cpu_starting(cpu);
+ sched_tick_start(cpu);
+ return 0;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+int sched_cpu_dying(unsigned int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+ struct rq_flags rf;
+
+ /* Handle pending wakeups and then migrate everything off */
+ sched_tick_stop(cpu);
+
+ rq_lock_irqsave(rq, &rf);
+ if (rq->rd) {
+ BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
+ set_rq_offline(rq);
+ }
+ migrate_tasks(rq, &rf);
+ BUG_ON(rq->nr_running != 1);
+ rq_unlock_irqrestore(rq, &rf);
+
+ calc_load_migrate(rq);
+ update_max_interval();
+ nohz_balance_exit_idle(rq);
+ hrtick_clear(rq);
+ return 0;
+}
+#endif
+
+void __init sched_init_smp(void)
+{
+ sched_init_numa();
+
+ /*
+ * There's no userspace yet to cause hotplug operations; hence all the
+ * CPU masks are stable and all blatant races in the below code cannot
+ * happen.
+ */
+ mutex_lock(&sched_domains_mutex);
+ sched_init_domains(cpu_active_mask);
+ mutex_unlock(&sched_domains_mutex);
+
+ /* Move init over to a non-isolated CPU */
+ if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)
+ BUG();
+ sched_init_granularity();
+
+ init_sched_rt_class();
+ init_sched_dl_class();
+
+ sched_smp_initialized = true;
+}
+
+static int __init migration_init(void)
+{
+ sched_cpu_starting(smp_processor_id());
+ return 0;
+}
+early_initcall(migration_init);
+
+#else
+void __init sched_init_smp(void)
+{
+ sched_init_granularity();
+}
+#endif /* CONFIG_SMP */
+
+int in_sched_functions(unsigned long addr)
+{
+ return in_lock_functions(addr) ||
+ (addr >= (unsigned long)__sched_text_start
+ && addr < (unsigned long)__sched_text_end);
+}
+
+#ifdef CONFIG_CGROUP_SCHED
+/*
+ * Default task group.
+ * Every task in system belongs to this group at bootup.
+ */
+struct task_group root_task_group;
+LIST_HEAD(task_groups);
+
+/* Cacheline aligned slab cache for task_group */
+static struct kmem_cache *task_group_cache __read_mostly;
+#endif
+
+DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
+DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
+
+void __init sched_init(void)
+{
+ unsigned long ptr = 0;
+ int i;
+
+ /* Make sure the linker didn't screw up */
+ BUG_ON(&idle_sched_class + 1 != &fair_sched_class ||
+ &fair_sched_class + 1 != &rt_sched_class ||
+ &rt_sched_class + 1 != &dl_sched_class);
+#ifdef CONFIG_SMP
+ BUG_ON(&dl_sched_class + 1 != &stop_sched_class);
+#endif
+
+ wait_bit_init();
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ ptr += 2 * nr_cpu_ids * sizeof(void **);
+#endif
+#ifdef CONFIG_RT_GROUP_SCHED
+ ptr += 2 * nr_cpu_ids * sizeof(void **);
+#endif
+ if (ptr) {
+ ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ root_task_group.se = (struct sched_entity **)ptr;
+ ptr += nr_cpu_ids * sizeof(void **);
+
+ root_task_group.cfs_rq = (struct cfs_rq **)ptr;
+ ptr += nr_cpu_ids * sizeof(void **);
+
+ root_task_group.shares = ROOT_TASK_GROUP_LOAD;
+ init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
+#endif /* CONFIG_FAIR_GROUP_SCHED */
+#ifdef CONFIG_RT_GROUP_SCHED
+ root_task_group.rt_se = (struct sched_rt_entity **)ptr;
+ ptr += nr_cpu_ids * sizeof(void **);
+
+ root_task_group.rt_rq = (struct rt_rq **)ptr;
+ ptr += nr_cpu_ids * sizeof(void **);
+
+#endif /* CONFIG_RT_GROUP_SCHED */
+ }
+#ifdef CONFIG_CPUMASK_OFFSTACK
+ for_each_possible_cpu(i) {
+ per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
+ cpumask_size(), GFP_KERNEL, cpu_to_node(i));
+ per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
+ cpumask_size(), GFP_KERNEL, cpu_to_node(i));
+ }
+#endif /* CONFIG_CPUMASK_OFFSTACK */
+
+ init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
+ init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime());
+
+#ifdef CONFIG_SMP
+ init_defrootdomain();
+#endif
+
+#ifdef CONFIG_RT_GROUP_SCHED
+ init_rt_bandwidth(&root_task_group.rt_bandwidth,
+ global_rt_period(), global_rt_runtime());
+#endif /* CONFIG_RT_GROUP_SCHED */
+
+#ifdef CONFIG_CGROUP_SCHED
+ task_group_cache = KMEM_CACHE(task_group, 0);
+
+ list_add(&root_task_group.list, &task_groups);
+ INIT_LIST_HEAD(&root_task_group.children);
+ INIT_LIST_HEAD(&root_task_group.siblings);
+ autogroup_init(&init_task);
+#endif /* CONFIG_CGROUP_SCHED */
+
+ for_each_possible_cpu(i) {
+ struct rq *rq;
+
+ rq = cpu_rq(i);
+ raw_spin_lock_init(&rq->lock);
+ rq->nr_running = 0;
+ rq->calc_load_active = 0;
+ rq->calc_load_update = jiffies + LOAD_FREQ;
+ init_cfs_rq(&rq->cfs);
+ init_rt_rq(&rq->rt);
+ init_dl_rq(&rq->dl);
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
+ rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
+ /*
+ * How much CPU bandwidth does root_task_group get?
+ *
+ * In case of task-groups formed thr' the cgroup filesystem, it
+ * gets 100% of the CPU resources in the system. This overall
+ * system CPU resource is divided among the tasks of
+ * root_task_group and its child task-groups in a fair manner,
+ * based on each entity's (task or task-group's) weight
+ * (se->load.weight).
+ *
+ * In other words, if root_task_group has 10 tasks of weight
+ * 1024) and two child groups A0 and A1 (of weight 1024 each),
+ * then A0's share of the CPU resource is:
+ *
+ * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
+ *
+ * We achieve this by letting root_task_group's tasks sit
+ * directly in rq->cfs (i.e root_task_group->se[] = NULL).
+ */
+ init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
+#endif /* CONFIG_FAIR_GROUP_SCHED */
+
+ rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
+#ifdef CONFIG_RT_GROUP_SCHED
+ init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
+#endif
+#ifdef CONFIG_SMP
+ rq->sd = NULL;
+ rq->rd = NULL;
+ rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
+ rq->balance_callback = NULL;
+ rq->active_balance = 0;
+ rq->next_balance = jiffies;
+ rq->push_cpu = 0;
+ rq->cpu = i;
+ rq->online = 0;
+ rq->idle_stamp = 0;
+ rq->avg_idle = 2*sysctl_sched_migration_cost;
+ rq->max_idle_balance_cost = sysctl_sched_migration_cost;
+
+ INIT_LIST_HEAD(&rq->cfs_tasks);
+
+ rq_attach_root(rq, &def_root_domain);
+#ifdef CONFIG_NO_HZ_COMMON
+ rq->last_blocked_load_update_tick = jiffies;
+ atomic_set(&rq->nohz_flags, 0);
+
+ rq_csd_init(rq, &rq->nohz_csd, nohz_csd_func);
+#endif
+#endif /* CONFIG_SMP */
+ hrtick_rq_init(rq);
+ atomic_set(&rq->nr_iowait, 0);
+ }
+
+ set_load_weight(&init_task);
+
+ /*
+ * The boot idle thread does lazy MMU switching as well:
+ */
+ mmgrab(&init_mm);
+ enter_lazy_tlb(&init_mm, current);
+
+ /*
+ * Make us the idle thread. Technically, schedule() should not be
+ * called from this thread, however somewhere below it might be,
+ * but because we are the idle thread, we just pick up running again
+ * when this runqueue becomes "idle".
+ */
+ init_idle(current, smp_processor_id());
+
+ calc_load_update = jiffies + LOAD_FREQ;
+
+#ifdef CONFIG_SMP
+ idle_thread_set_boot_cpu();
+#endif
+ init_sched_fair_class();
+
+ init_schedstats();
+
+ psi_init();
+
+ init_uclamp();
+
+ scheduler_running = 1;
+}
+
+#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
+static inline int preempt_count_equals(int preempt_offset)
+{
+ int nested = preempt_count() + rcu_preempt_depth();
+
+ return (nested == preempt_offset);
+}
+
+void __might_sleep(const char *file, int line, int preempt_offset)
+{
+ /*
+ * Blocking primitives will set (and therefore destroy) current->state,
+ * since we will exit with TASK_RUNNING make sure we enter with it,
+ * otherwise we will destroy state.
+ */
+ WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
+ "do not call blocking ops when !TASK_RUNNING; "
+ "state=%lx set at [<%p>] %pS\n",
+ current->state,
+ (void *)current->task_state_change,
+ (void *)current->task_state_change);
+
+ ___might_sleep(file, line, preempt_offset);
+}
+EXPORT_SYMBOL(__might_sleep);
+
+void ___might_sleep(const char *file, int line, int preempt_offset)
+{
+ /* Ratelimiting timestamp: */
+ static unsigned long prev_jiffy;
+
+ unsigned long preempt_disable_ip;
+
+ /* WARN_ON_ONCE() by default, no rate limit required: */
+ rcu_sleep_check();
+
+ if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
+ !is_idle_task(current) && !current->non_block_count) ||
+ system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
+ oops_in_progress)
+ return;
+
+ if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
+ return;
+ prev_jiffy = jiffies;
+
+ /* Save this before calling printk(), since that will clobber it: */
+ preempt_disable_ip = get_preempt_disable_ip(current);
+
+ printk(KERN_ERR
+ "BUG: sleeping function called from invalid context at %s:%d\n",
+ file, line);
+ printk(KERN_ERR
+ "in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
+ in_atomic(), irqs_disabled(), current->non_block_count,
+ current->pid, current->comm);
+
+ if (task_stack_end_corrupted(current))
+ printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
+
+ debug_show_held_locks(current);
+ if (irqs_disabled())
+ print_irqtrace_events(current);
+ if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
+ && !preempt_count_equals(preempt_offset)) {
+ pr_err("Preemption disabled at:");
+ print_ip_sym(KERN_ERR, preempt_disable_ip);
+ }
+ dump_stack();
+ add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
+}
+EXPORT_SYMBOL(___might_sleep);
+
+void __cant_sleep(const char *file, int line, int preempt_offset)
+{
+ static unsigned long prev_jiffy;
+
+ if (irqs_disabled())
+ return;
+
+ if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
+ return;
+
+ if (preempt_count() > preempt_offset)
+ return;
+
+ if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
+ return;
+ prev_jiffy = jiffies;
+
+ printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
+ printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
+ in_atomic(), irqs_disabled(),
+ current->pid, current->comm);
+
+ debug_show_held_locks(current);
+ dump_stack();
+ add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
+}
+EXPORT_SYMBOL_GPL(__cant_sleep);
+#endif
+
+#ifdef CONFIG_MAGIC_SYSRQ
+void normalize_rt_tasks(void)
+{
+ struct task_struct *g, *p;
+ struct sched_attr attr = {
+ .sched_policy = SCHED_NORMAL,
+ };
+
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, p) {
+ /*
+ * Only normalize user tasks:
+ */
+ if (p->flags & PF_KTHREAD)
+ continue;
+
+ p->se.exec_start = 0;
+ schedstat_set(p->se.statistics.wait_start, 0);
+ schedstat_set(p->se.statistics.sleep_start, 0);
+ schedstat_set(p->se.statistics.block_start, 0);
+
+ if (!dl_task(p) && !rt_task(p)) {
+ /*
+ * Renice negative nice level userspace
+ * tasks back to 0:
+ */
+ if (task_nice(p) < 0)
+ set_user_nice(p, 0);
+ continue;
+ }
+
+ __sched_setscheduler(p, &attr, false, false);
+ }
+ read_unlock(&tasklist_lock);
+}
+
+#endif /* CONFIG_MAGIC_SYSRQ */
+
+#if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
+/*
+ * These functions are only useful for the IA64 MCA handling, or kdb.
+ *
+ * They can only be called when the whole system has been
+ * stopped - every CPU needs to be quiescent, and no scheduling
+ * activity can take place. Using them for anything else would
+ * be a serious bug, and as a result, they aren't even visible
+ * under any other configuration.
+ */
+
+/**
+ * curr_task - return the current task for a given CPU.
+ * @cpu: the processor in question.
+ *
+ * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
+ *
+ * Return: The current task for @cpu.
+ */
+struct task_struct *curr_task(int cpu)
+{
+ return cpu_curr(cpu);
+}
+
+#endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
+
+#ifdef CONFIG_IA64
+/**
+ * ia64_set_curr_task - set the current task for a given CPU.
+ * @cpu: the processor in question.
+ * @p: the task pointer to set.
+ *
+ * Description: This function must only be used when non-maskable interrupts
+ * are serviced on a separate stack. It allows the architecture to switch the
+ * notion of the current task on a CPU in a non-blocking manner. This function
+ * must be called with all CPU's synchronized, and interrupts disabled, the
+ * and caller must save the original value of the current task (see
+ * curr_task() above) and restore that value before reenabling interrupts and
+ * re-starting the system.
+ *
+ * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
+ */
+void ia64_set_curr_task(int cpu, struct task_struct *p)
+{
+ cpu_curr(cpu) = p;
+}
+
+#endif
+
+#ifdef CONFIG_CGROUP_SCHED
+/* task_group_lock serializes the addition/removal of task groups */
+static DEFINE_SPINLOCK(task_group_lock);
+
+static inline void alloc_uclamp_sched_group(struct task_group *tg,
+ struct task_group *parent)
+{
+#ifdef CONFIG_UCLAMP_TASK_GROUP
+ enum uclamp_id clamp_id;
+
+ for_each_clamp_id(clamp_id) {
+ uclamp_se_set(&tg->uclamp_req[clamp_id],
+ uclamp_none(clamp_id), false);
+ tg->uclamp[clamp_id] = parent->uclamp[clamp_id];
+ }
+#endif
+}
+
+static void sched_free_group(struct task_group *tg)
+{
+ free_fair_sched_group(tg);
+ free_rt_sched_group(tg);
+ autogroup_free(tg);
+ kmem_cache_free(task_group_cache, tg);
+}
+
+/* allocate runqueue etc for a new task group */
+struct task_group *sched_create_group(struct task_group *parent)
+{
+ struct task_group *tg;
+
+ tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
+ if (!tg)
+ return ERR_PTR(-ENOMEM);
+
+ if (!alloc_fair_sched_group(tg, parent))
+ goto err;
+
+ if (!alloc_rt_sched_group(tg, parent))
+ goto err;
+
+ alloc_uclamp_sched_group(tg, parent);
+
+ return tg;
+
+err:
+ sched_free_group(tg);
+ return ERR_PTR(-ENOMEM);
+}
+
+void sched_online_group(struct task_group *tg, struct task_group *parent)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&task_group_lock, flags);
+ list_add_rcu(&tg->list, &task_groups);
+
+ /* Root should already exist: */
+ WARN_ON(!parent);
+
+ tg->parent = parent;
+ INIT_LIST_HEAD(&tg->children);
+ list_add_rcu(&tg->siblings, &parent->children);
+ spin_unlock_irqrestore(&task_group_lock, flags);
+
+ online_fair_sched_group(tg);
+}
+
+/* rcu callback to free various structures associated with a task group */
+static void sched_free_group_rcu(struct rcu_head *rhp)
+{
+ /* Now it should be safe to free those cfs_rqs: */
+ sched_free_group(container_of(rhp, struct task_group, rcu));
+}
+
+void sched_destroy_group(struct task_group *tg)
+{
+ /* Wait for possible concurrent references to cfs_rqs complete: */
+ call_rcu(&tg->rcu, sched_free_group_rcu);
+}
+
+void sched_offline_group(struct task_group *tg)
+{
+ unsigned long flags;
+
+ /* End participation in shares distribution: */
+ unregister_fair_sched_group(tg);
+
+ spin_lock_irqsave(&task_group_lock, flags);
+ list_del_rcu(&tg->list);
+ list_del_rcu(&tg->siblings);
+ spin_unlock_irqrestore(&task_group_lock, flags);
+}
+
+static void sched_change_group(struct task_struct *tsk, int type)
+{
+ struct task_group *tg;
+
+ /*
+ * All callers are synchronized by task_rq_lock(); we do not use RCU
+ * which is pointless here. Thus, we pass "true" to task_css_check()
+ * to prevent lockdep warnings.
+ */
+ tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
+ struct task_group, css);
+ tg = autogroup_task_group(tsk, tg);
+ tsk->sched_task_group = tg;
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ if (tsk->sched_class->task_change_group)
+ tsk->sched_class->task_change_group(tsk, type);
+ else
+#endif
+ set_task_rq(tsk, task_cpu(tsk));
+}
+
+/*
+ * Change task's runqueue when it moves between groups.
+ *
+ * The caller of this function should have put the task in its new group by
+ * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
+ * its new group.
+ */
+void sched_move_task(struct task_struct *tsk)
+{
+ int queued, running, queue_flags =
+ DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
+ struct rq_flags rf;
+ struct rq *rq;
+
+ rq = task_rq_lock(tsk, &rf);
+ update_rq_clock(rq);
+
+ running = task_current(rq, tsk);
+ queued = task_on_rq_queued(tsk);
+
+ if (queued)
+ dequeue_task(rq, tsk, queue_flags);
+ if (running)
+ put_prev_task(rq, tsk);
+
+ sched_change_group(tsk, TASK_MOVE_GROUP);
+
+ if (queued)
+ enqueue_task(rq, tsk, queue_flags);
+ if (running) {
+ set_next_task(rq, tsk);
+ /*
+ * After changing group, the running task may have joined a
+ * throttled one but it's still the running task. Trigger a
+ * resched to make sure that task can still run.
+ */
+ resched_curr(rq);
+ }
+
+ task_rq_unlock(rq, tsk, &rf);
+}
+
+static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
+{
+ return css ? container_of(css, struct task_group, css) : NULL;
+}
+
+static struct cgroup_subsys_state *
+cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
+{
+ struct task_group *parent = css_tg(parent_css);
+ struct task_group *tg;
+
+ if (!parent) {
+ /* This is early initialization for the top cgroup */
+ return &root_task_group.css;
+ }
+
+ tg = sched_create_group(parent);
+ if (IS_ERR(tg))
+ return ERR_PTR(-ENOMEM);
+
+ return &tg->css;
+}
+
+/* Expose task group only after completing cgroup initialization */
+static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
+{
+ struct task_group *tg = css_tg(css);
+ struct task_group *parent = css_tg(css->parent);
+
+ if (parent)
+ sched_online_group(tg, parent);
+
+#ifdef CONFIG_UCLAMP_TASK_GROUP
+ /* Propagate the effective uclamp value for the new group */
+ mutex_lock(&uclamp_mutex);
+ rcu_read_lock();
+ cpu_util_update_eff(css);
+ rcu_read_unlock();
+ mutex_unlock(&uclamp_mutex);
+#endif
+
+ return 0;
+}
+
+static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
+{
+ struct task_group *tg = css_tg(css);
+
+ sched_offline_group(tg);
+}
+
+static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
+{
+ struct task_group *tg = css_tg(css);
+
+ /*
+ * Relies on the RCU grace period between css_released() and this.
+ */
+ sched_free_group(tg);
+}
+
+/*
+ * This is called before wake_up_new_task(), therefore we really only
+ * have to set its group bits, all the other stuff does not apply.
+ */
+static void cpu_cgroup_fork(struct task_struct *task)
+{
+ struct rq_flags rf;
+ struct rq *rq;
+
+ rq = task_rq_lock(task, &rf);
+
+ update_rq_clock(rq);
+ sched_change_group(task, TASK_SET_GROUP);
+
+ task_rq_unlock(rq, task, &rf);
+}
+
+static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
+{
+ struct task_struct *task;
+ struct cgroup_subsys_state *css;
+ int ret = 0;
+
+ cgroup_taskset_for_each(task, css, tset) {
+#ifdef CONFIG_RT_GROUP_SCHED
+ if (!sched_rt_can_attach(css_tg(css), task))
+ return -EINVAL;
+#endif
+ /*
+ * Serialize against wake_up_new_task() such that if its
+ * running, we're sure to observe its full state.
+ */
+ raw_spin_lock_irq(&task->pi_lock);
+ /*
+ * Avoid calling sched_move_task() before wake_up_new_task()
+ * has happened. This would lead to problems with PELT, due to
+ * move wanting to detach+attach while we're not attached yet.
+ */
+ if (task->state == TASK_NEW)
+ ret = -EINVAL;
+ raw_spin_unlock_irq(&task->pi_lock);
+
+ if (ret)
+ break;
+ }
+ return ret;
+}
+
+static void cpu_cgroup_attach(struct cgroup_taskset *tset)
+{
+ struct task_struct *task;
+ struct cgroup_subsys_state *css;
+
+ cgroup_taskset_for_each(task, css, tset)
+ sched_move_task(task);
+}
+
+#ifdef CONFIG_UCLAMP_TASK_GROUP
+static void cpu_util_update_eff(struct cgroup_subsys_state *css)
+{
+ struct cgroup_subsys_state *top_css = css;
+ struct uclamp_se *uc_parent = NULL;
+ struct uclamp_se *uc_se = NULL;
+ unsigned int eff[UCLAMP_CNT];
+ enum uclamp_id clamp_id;
+ unsigned int clamps;
+
+ lockdep_assert_held(&uclamp_mutex);
+ SCHED_WARN_ON(!rcu_read_lock_held());
+
+ css_for_each_descendant_pre(css, top_css) {
+ uc_parent = css_tg(css)->parent
+ ? css_tg(css)->parent->uclamp : NULL;
+
+ for_each_clamp_id(clamp_id) {
+ /* Assume effective clamps matches requested clamps */
+ eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value;
+ /* Cap effective clamps with parent's effective clamps */
+ if (uc_parent &&
+ eff[clamp_id] > uc_parent[clamp_id].value) {
+ eff[clamp_id] = uc_parent[clamp_id].value;
+ }
+ }
+ /* Ensure protection is always capped by limit */
+ eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]);
+
+ /* Propagate most restrictive effective clamps */
+ clamps = 0x0;
+ uc_se = css_tg(css)->uclamp;
+ for_each_clamp_id(clamp_id) {
+ if (eff[clamp_id] == uc_se[clamp_id].value)
+ continue;
+ uc_se[clamp_id].value = eff[clamp_id];
+ uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]);
+ clamps |= (0x1 << clamp_id);
+ }
+ if (!clamps) {
+ css = css_rightmost_descendant(css);
+ continue;
+ }
+
+ /* Immediately update descendants RUNNABLE tasks */
+ uclamp_update_active_tasks(css);
+ }
+}
+
+/*
+ * Integer 10^N with a given N exponent by casting to integer the literal "1eN"
+ * C expression. Since there is no way to convert a macro argument (N) into a
+ * character constant, use two levels of macros.
+ */
+#define _POW10(exp) ((unsigned int)1e##exp)
+#define POW10(exp) _POW10(exp)
+
+struct uclamp_request {
+#define UCLAMP_PERCENT_SHIFT 2
+#define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT))
+ s64 percent;
+ u64 util;
+ int ret;
+};
+
+static inline struct uclamp_request
+capacity_from_percent(char *buf)
+{
+ struct uclamp_request req = {
+ .percent = UCLAMP_PERCENT_SCALE,
+ .util = SCHED_CAPACITY_SCALE,
+ .ret = 0,
+ };
+
+ buf = strim(buf);
+ if (strcmp(buf, "max")) {
+ req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT,
+ &req.percent);
+ if (req.ret)
+ return req;
+ if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
+ req.ret = -ERANGE;
+ return req;
+ }
+
+ req.util = req.percent << SCHED_CAPACITY_SHIFT;
+ req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE);
+ }
+
+ return req;
+}
+
+static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off,
+ enum uclamp_id clamp_id)
+{
+ struct uclamp_request req;
+ struct task_group *tg;
+
+ req = capacity_from_percent(buf);
+ if (req.ret)
+ return req.ret;
+
+ static_branch_enable(&sched_uclamp_used);
+
+ mutex_lock(&uclamp_mutex);
+ rcu_read_lock();
+
+ tg = css_tg(of_css(of));
+ if (tg->uclamp_req[clamp_id].value != req.util)
+ uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false);
+
+ /*
+ * Because of not recoverable conversion rounding we keep track of the
+ * exact requested value
+ */
+ tg->uclamp_pct[clamp_id] = req.percent;
+
+ /* Update effective clamps to track the most restrictive value */
+ cpu_util_update_eff(of_css(of));
+
+ rcu_read_unlock();
+ mutex_unlock(&uclamp_mutex);
+
+ return nbytes;
+}
+
+static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN);
+}
+
+static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX);
+}
+
+static inline void cpu_uclamp_print(struct seq_file *sf,
+ enum uclamp_id clamp_id)
+{
+ struct task_group *tg;
+ u64 util_clamp;
+ u64 percent;
+ u32 rem;
+
+ rcu_read_lock();
+ tg = css_tg(seq_css(sf));
+ util_clamp = tg->uclamp_req[clamp_id].value;
+ rcu_read_unlock();
+
+ if (util_clamp == SCHED_CAPACITY_SCALE) {
+ seq_puts(sf, "max\n");
+ return;
+ }
+
+ percent = tg->uclamp_pct[clamp_id];
+ percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem);
+ seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem);
+}
+
+static int cpu_uclamp_min_show(struct seq_file *sf, void *v)
+{
+ cpu_uclamp_print(sf, UCLAMP_MIN);
+ return 0;
+}
+
+static int cpu_uclamp_max_show(struct seq_file *sf, void *v)
+{
+ cpu_uclamp_print(sf, UCLAMP_MAX);
+ return 0;
+}
+#endif /* CONFIG_UCLAMP_TASK_GROUP */
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
+ struct cftype *cftype, u64 shareval)
+{
+ if (shareval > scale_load_down(ULONG_MAX))
+ shareval = MAX_SHARES;
+ return sched_group_set_shares(css_tg(css), scale_load(shareval));
+}
+
+static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ struct task_group *tg = css_tg(css);
+
+ return (u64) scale_load_down(tg->shares);
+}
+
+#ifdef CONFIG_CFS_BANDWIDTH
+static DEFINE_MUTEX(cfs_constraints_mutex);
+
+const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
+static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
+/* More than 203 days if BW_SHIFT equals 20. */
+static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
+
+static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
+
+static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
+{
+ int i, ret = 0, runtime_enabled, runtime_was_enabled;
+ struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
+
+ if (tg == &root_task_group)
+ return -EINVAL;
+
+ /*
+ * Ensure we have at some amount of bandwidth every period. This is
+ * to prevent reaching a state of large arrears when throttled via
+ * entity_tick() resulting in prolonged exit starvation.
+ */
+ if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
+ return -EINVAL;
+
+ /*
+ * Likewise, bound things on the otherside by preventing insane quota
+ * periods. This also allows us to normalize in computing quota
+ * feasibility.
+ */
+ if (period > max_cfs_quota_period)
+ return -EINVAL;
+
+ /*
+ * Bound quota to defend quota against overflow during bandwidth shift.
+ */
+ if (quota != RUNTIME_INF && quota > max_cfs_runtime)
+ return -EINVAL;
+
+ /*
+ * Prevent race between setting of cfs_rq->runtime_enabled and
+ * unthrottle_offline_cfs_rqs().
+ */
+ get_online_cpus();
+ mutex_lock(&cfs_constraints_mutex);
+ ret = __cfs_schedulable(tg, period, quota);
+ if (ret)
+ goto out_unlock;
+
+ runtime_enabled = quota != RUNTIME_INF;
+ runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
+ /*
+ * If we need to toggle cfs_bandwidth_used, off->on must occur
+ * before making related changes, and on->off must occur afterwards
+ */
+ if (runtime_enabled && !runtime_was_enabled)
+ cfs_bandwidth_usage_inc();
+ raw_spin_lock_irq(&cfs_b->lock);
+ cfs_b->period = ns_to_ktime(period);
+ cfs_b->quota = quota;
+
+ __refill_cfs_bandwidth_runtime(cfs_b);
+
+ /* Restart the period timer (if active) to handle new period expiry: */
+ if (runtime_enabled)
+ start_cfs_bandwidth(cfs_b);
+
+ raw_spin_unlock_irq(&cfs_b->lock);
+
+ for_each_online_cpu(i) {
+ struct cfs_rq *cfs_rq = tg->cfs_rq[i];
+ struct rq *rq = cfs_rq->rq;
+ struct rq_flags rf;
+
+ rq_lock_irq(rq, &rf);
+ cfs_rq->runtime_enabled = runtime_enabled;
+ cfs_rq->runtime_remaining = 0;
+
+ if (cfs_rq->throttled)
+ unthrottle_cfs_rq(cfs_rq);
+ rq_unlock_irq(rq, &rf);
+ }
+ if (runtime_was_enabled && !runtime_enabled)
+ cfs_bandwidth_usage_dec();
+out_unlock:
+ mutex_unlock(&cfs_constraints_mutex);
+ put_online_cpus();
+
+ return ret;
+}
+
+static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
+{
+ u64 quota, period;
+
+ period = ktime_to_ns(tg->cfs_bandwidth.period);
+ if (cfs_quota_us < 0)
+ quota = RUNTIME_INF;
+ else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
+ quota = (u64)cfs_quota_us * NSEC_PER_USEC;
+ else
+ return -EINVAL;
+
+ return tg_set_cfs_bandwidth(tg, period, quota);
+}
+
+static long tg_get_cfs_quota(struct task_group *tg)
+{
+ u64 quota_us;
+
+ if (tg->cfs_bandwidth.quota == RUNTIME_INF)
+ return -1;
+
+ quota_us = tg->cfs_bandwidth.quota;
+ do_div(quota_us, NSEC_PER_USEC);
+
+ return quota_us;
+}
+
+static int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
+{
+ u64 quota, period;
+
+ if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC)
+ return -EINVAL;
+
+ period = (u64)cfs_period_us * NSEC_PER_USEC;
+ quota = tg->cfs_bandwidth.quota;
+
+ return tg_set_cfs_bandwidth(tg, period, quota);
+}
+
+static long tg_get_cfs_period(struct task_group *tg)
+{
+ u64 cfs_period_us;
+
+ cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
+ do_div(cfs_period_us, NSEC_PER_USEC);
+
+ return cfs_period_us;
+}
+
+static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return tg_get_cfs_quota(css_tg(css));
+}
+
+static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
+ struct cftype *cftype, s64 cfs_quota_us)
+{
+ return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
+}
+
+static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return tg_get_cfs_period(css_tg(css));
+}
+
+static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
+ struct cftype *cftype, u64 cfs_period_us)
+{
+ return tg_set_cfs_period(css_tg(css), cfs_period_us);
+}
+
+struct cfs_schedulable_data {
+ struct task_group *tg;
+ u64 period, quota;
+};
+
+/*
+ * normalize group quota/period to be quota/max_period
+ * note: units are usecs
+ */
+static u64 normalize_cfs_quota(struct task_group *tg,
+ struct cfs_schedulable_data *d)
+{
+ u64 quota, period;
+
+ if (tg == d->tg) {
+ period = d->period;
+ quota = d->quota;
+ } else {
+ period = tg_get_cfs_period(tg);
+ quota = tg_get_cfs_quota(tg);
+ }
+
+ /* note: these should typically be equivalent */
+ if (quota == RUNTIME_INF || quota == -1)
+ return RUNTIME_INF;
+
+ return to_ratio(period, quota);
+}
+
+static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
+{
+ struct cfs_schedulable_data *d = data;
+ struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
+ s64 quota = 0, parent_quota = -1;
+
+ if (!tg->parent) {
+ quota = RUNTIME_INF;
+ } else {
+ struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
+
+ quota = normalize_cfs_quota(tg, d);
+ parent_quota = parent_b->hierarchical_quota;
+
+ /*
+ * Ensure max(child_quota) <= parent_quota. On cgroup2,
+ * always take the min. On cgroup1, only inherit when no
+ * limit is set:
+ */
+ if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) {
+ quota = min(quota, parent_quota);
+ } else {
+ if (quota == RUNTIME_INF)
+ quota = parent_quota;
+ else if (parent_quota != RUNTIME_INF && quota > parent_quota)
+ return -EINVAL;
+ }
+ }
+ cfs_b->hierarchical_quota = quota;
+
+ return 0;
+}
+
+static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
+{
+ int ret;
+ struct cfs_schedulable_data data = {
+ .tg = tg,
+ .period = period,
+ .quota = quota,
+ };
+
+ if (quota != RUNTIME_INF) {
+ do_div(data.period, NSEC_PER_USEC);
+ do_div(data.quota, NSEC_PER_USEC);
+ }
+
+ rcu_read_lock();
+ ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
+ rcu_read_unlock();
+
+ return ret;
+}
+
+static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
+{
+ struct task_group *tg = css_tg(seq_css(sf));
+ struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
+
+ seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
+ seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
+ seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
+
+ if (schedstat_enabled() && tg != &root_task_group) {
+ u64 ws = 0;
+ int i;
+
+ for_each_possible_cpu(i)
+ ws += schedstat_val(tg->se[i]->statistics.wait_sum);
+
+ seq_printf(sf, "wait_sum %llu\n", ws);
+ }
+
+ return 0;
+}
+#endif /* CONFIG_CFS_BANDWIDTH */
+#endif /* CONFIG_FAIR_GROUP_SCHED */
+
+#ifdef CONFIG_RT_GROUP_SCHED
+static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
+ struct cftype *cft, s64 val)
+{
+ return sched_group_set_rt_runtime(css_tg(css), val);
+}
+
+static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return sched_group_rt_runtime(css_tg(css));
+}
+
+static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
+ struct cftype *cftype, u64 rt_period_us)
+{
+ return sched_group_set_rt_period(css_tg(css), rt_period_us);
+}
+
+static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return sched_group_rt_period(css_tg(css));
+}
+#endif /* CONFIG_RT_GROUP_SCHED */
+
+static struct cftype cpu_legacy_files[] = {
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ {
+ .name = "shares",
+ .read_u64 = cpu_shares_read_u64,
+ .write_u64 = cpu_shares_write_u64,
+ },
+#endif
+#ifdef CONFIG_CFS_BANDWIDTH
+ {
+ .name = "cfs_quota_us",
+ .read_s64 = cpu_cfs_quota_read_s64,
+ .write_s64 = cpu_cfs_quota_write_s64,
+ },
+ {
+ .name = "cfs_period_us",
+ .read_u64 = cpu_cfs_period_read_u64,
+ .write_u64 = cpu_cfs_period_write_u64,
+ },
+ {
+ .name = "stat",
+ .seq_show = cpu_cfs_stat_show,
+ },
+#endif
+#ifdef CONFIG_RT_GROUP_SCHED
+ {
+ .name = "rt_runtime_us",
+ .read_s64 = cpu_rt_runtime_read,
+ .write_s64 = cpu_rt_runtime_write,
+ },
+ {
+ .name = "rt_period_us",
+ .read_u64 = cpu_rt_period_read_uint,
+ .write_u64 = cpu_rt_period_write_uint,
+ },
+#endif
+#ifdef CONFIG_UCLAMP_TASK_GROUP
+ {
+ .name = "uclamp.min",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = cpu_uclamp_min_show,
+ .write = cpu_uclamp_min_write,
+ },
+ {
+ .name = "uclamp.max",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = cpu_uclamp_max_show,
+ .write = cpu_uclamp_max_write,
+ },
+#endif
+ { } /* Terminate */
+};
+
+static int cpu_extra_stat_show(struct seq_file *sf,
+ struct cgroup_subsys_state *css)
+{
+#ifdef CONFIG_CFS_BANDWIDTH
+ {
+ struct task_group *tg = css_tg(css);
+ struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
+ u64 throttled_usec;
+
+ throttled_usec = cfs_b->throttled_time;
+ do_div(throttled_usec, NSEC_PER_USEC);
+
+ seq_printf(sf, "nr_periods %d\n"
+ "nr_throttled %d\n"
+ "throttled_usec %llu\n",
+ cfs_b->nr_periods, cfs_b->nr_throttled,
+ throttled_usec);
+ }
+#endif
+ return 0;
+}
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ struct task_group *tg = css_tg(css);
+ u64 weight = scale_load_down(tg->shares);
+
+ return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024);
+}
+
+static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
+ struct cftype *cft, u64 weight)
+{
+ /*
+ * cgroup weight knobs should use the common MIN, DFL and MAX
+ * values which are 1, 100 and 10000 respectively. While it loses
+ * a bit of range on both ends, it maps pretty well onto the shares
+ * value used by scheduler and the round-trip conversions preserve
+ * the original value over the entire range.
+ */
+ if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX)
+ return -ERANGE;
+
+ weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL);
+
+ return sched_group_set_shares(css_tg(css), scale_load(weight));
+}
+
+static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ unsigned long weight = scale_load_down(css_tg(css)->shares);
+ int last_delta = INT_MAX;
+ int prio, delta;
+
+ /* find the closest nice value to the current weight */
+ for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) {
+ delta = abs(sched_prio_to_weight[prio] - weight);
+ if (delta >= last_delta)
+ break;
+ last_delta = delta;
+ }
+
+ return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO);
+}
+
+static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
+ struct cftype *cft, s64 nice)
+{
+ unsigned long weight;
+ int idx;
+
+ if (nice < MIN_NICE || nice > MAX_NICE)
+ return -ERANGE;
+
+ idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
+ idx = array_index_nospec(idx, 40);
+ weight = sched_prio_to_weight[idx];
+
+ return sched_group_set_shares(css_tg(css), scale_load(weight));
+}
+#endif
+
+static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
+ long period, long quota)
+{
+ if (quota < 0)
+ seq_puts(sf, "max");
+ else
+ seq_printf(sf, "%ld", quota);
+
+ seq_printf(sf, " %ld\n", period);
+}
+
+/* caller should put the current value in *@periodp before calling */
+static int __maybe_unused cpu_period_quota_parse(char *buf,
+ u64 *periodp, u64 *quotap)
+{
+ char tok[21]; /* U64_MAX */
+
+ if (sscanf(buf, "%20s %llu", tok, periodp) < 1)
+ return -EINVAL;
+
+ *periodp *= NSEC_PER_USEC;
+
+ if (sscanf(tok, "%llu", quotap))
+ *quotap *= NSEC_PER_USEC;
+ else if (!strcmp(tok, "max"))
+ *quotap = RUNTIME_INF;
+ else
+ return -EINVAL;
+
+ return 0;
+}
+
+#ifdef CONFIG_CFS_BANDWIDTH
+static int cpu_max_show(struct seq_file *sf, void *v)
+{
+ struct task_group *tg = css_tg(seq_css(sf));
+
+ cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg));
+ return 0;
+}
+
+static ssize_t cpu_max_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct task_group *tg = css_tg(of_css(of));
+ u64 period = tg_get_cfs_period(tg);
+ u64 quota;
+ int ret;
+
+ ret = cpu_period_quota_parse(buf, &period, &quota);
+ if (!ret)
+ ret = tg_set_cfs_bandwidth(tg, period, quota);
+ return ret ?: nbytes;
+}
+#endif
+
+static struct cftype cpu_files[] = {
+#ifdef CONFIG_FAIR_GROUP_SCHED
+ {
+ .name = "weight",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .read_u64 = cpu_weight_read_u64,
+ .write_u64 = cpu_weight_write_u64,
+ },
+ {
+ .name = "weight.nice",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .read_s64 = cpu_weight_nice_read_s64,
+ .write_s64 = cpu_weight_nice_write_s64,
+ },
+#endif
+#ifdef CONFIG_CFS_BANDWIDTH
+ {
+ .name = "max",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = cpu_max_show,
+ .write = cpu_max_write,
+ },
+#endif
+#ifdef CONFIG_UCLAMP_TASK_GROUP
+ {
+ .name = "uclamp.min",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = cpu_uclamp_min_show,
+ .write = cpu_uclamp_min_write,
+ },
+ {
+ .name = "uclamp.max",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = cpu_uclamp_max_show,
+ .write = cpu_uclamp_max_write,
+ },
+#endif
+ { } /* terminate */
+};
+
+struct cgroup_subsys cpu_cgrp_subsys = {
+ .css_alloc = cpu_cgroup_css_alloc,
+ .css_online = cpu_cgroup_css_online,
+ .css_released = cpu_cgroup_css_released,
+ .css_free = cpu_cgroup_css_free,
+ .css_extra_stat_show = cpu_extra_stat_show,
+ .fork = cpu_cgroup_fork,
+ .can_attach = cpu_cgroup_can_attach,
+ .attach = cpu_cgroup_attach,
+ .legacy_cftypes = cpu_legacy_files,
+ .dfl_cftypes = cpu_files,
+ .early_init = true,
+ .threaded = true,
+};
+
+#endif /* CONFIG_CGROUP_SCHED */
+
+void dump_cpu_task(int cpu)
+{
+ pr_info("Task dump for CPU %d:\n", cpu);
+ sched_show_task(cpu_curr(cpu));
+}
+
+/*
+ * Nice levels are multiplicative, with a gentle 10% change for every
+ * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
+ * nice 1, it will get ~10% less CPU time than another CPU-bound task
+ * that remained on nice 0.
+ *
+ * The "10% effect" is relative and cumulative: from _any_ nice level,
+ * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
+ * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
+ * If a task goes up by ~10% and another task goes down by ~10% then
+ * the relative distance between them is ~25%.)
+ */
+const int sched_prio_to_weight[40] = {
+ /* -20 */ 88761, 71755, 56483, 46273, 36291,
+ /* -15 */ 29154, 23254, 18705, 14949, 11916,
+ /* -10 */ 9548, 7620, 6100, 4904, 3906,
+ /* -5 */ 3121, 2501, 1991, 1586, 1277,
+ /* 0 */ 1024, 820, 655, 526, 423,
+ /* 5 */ 335, 272, 215, 172, 137,
+ /* 10 */ 110, 87, 70, 56, 45,
+ /* 15 */ 36, 29, 23, 18, 15,
+};
+
+/*
+ * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
+ *
+ * In cases where the weight does not change often, we can use the
+ * precalculated inverse to speed up arithmetics by turning divisions
+ * into multiplications:
+ */
+const u32 sched_prio_to_wmult[40] = {
+ /* -20 */ 48388, 59856, 76040, 92818, 118348,
+ /* -15 */ 147320, 184698, 229616, 287308, 360437,
+ /* -10 */ 449829, 563644, 704093, 875809, 1099582,
+ /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
+ /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
+ /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
+ /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
+ /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
+};
+
+void call_trace_sched_update_nr_running(struct rq *rq, int count)
+{
+ trace_sched_update_nr_running_tp(rq, count);
+}