| /* |
| * kernel/sched/core.c |
| * |
| * Core kernel scheduler code and related syscalls |
| * |
| * Copyright (C) 1991-2002 Linus Torvalds |
| */ |
| #include <linux/sched.h> |
| #include <linux/sched/clock.h> |
| #include <uapi/linux/sched/types.h> |
| #include <linux/sched/loadavg.h> |
| #include <linux/sched/hotplug.h> |
| #include <linux/wait_bit.h> |
| #include <linux/cpuset.h> |
| #include <linux/delayacct.h> |
| #include <linux/init_task.h> |
| #include <linux/context_tracking.h> |
| #include <linux/rcupdate_wait.h> |
| |
| #include <linux/blkdev.h> |
| #include <linux/kprobes.h> |
| #include <linux/mmu_context.h> |
| #include <linux/module.h> |
| #include <linux/nmi.h> |
| #include <linux/prefetch.h> |
| #include <linux/profile.h> |
| #include <linux/security.h> |
| #include <linux/syscalls.h> |
| |
| #include <asm/switch_to.h> |
| #include <asm/tlb.h> |
| #ifdef CONFIG_PARAVIRT |
| #include <asm/paravirt.h> |
| #endif |
| |
| #include "sched.h" |
| #include "../workqueue_internal.h" |
| #include "../smpboot.h" |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/sched.h> |
| |
| DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); |
| |
| /* |
| * Debugging: various feature bits |
| */ |
| |
| #define SCHED_FEAT(name, enabled) \ |
| (1UL << __SCHED_FEAT_##name) * enabled | |
| |
| const_debug unsigned int sysctl_sched_features = |
| #include "features.h" |
| 0; |
| |
| #undef SCHED_FEAT |
| |
| /* |
| * 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 average the RT time consumption, measured |
| * in ms. |
| * |
| * default: 1s |
| */ |
| const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC; |
| |
| /* |
| * 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; |
| |
| /* CPUs with isolated domains */ |
| cpumask_var_t cpu_isolated_map; |
| |
| /* |
| * __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 acquire will |
| * pair with the WMB to ensure we must 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... |
| */ |
| #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING) |
| s64 steal = 0, irq_delta = 0; |
| #endif |
| #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((¶virt_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; |
| |
| #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING) |
| if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY)) |
| sched_rt_avg_update(rq, irq_delta + steal); |
| #endif |
| } |
| |
| 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); |
| } |
| |
| |
| #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; |
| |
| hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED); |
| } |
| |
| /* |
| * 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->hrtick_csd_pending = 0; |
| 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; |
| ktime_t time; |
| 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); |
| time = ktime_add_ns(timer->base->get_time(), delta); |
| |
| hrtimer_set_expires(timer, time); |
| |
| if (rq == this_rq()) { |
| __hrtick_restart(rq); |
| } else if (!rq->hrtick_csd_pending) { |
| smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd); |
| rq->hrtick_csd_pending = 1; |
| } |
| } |
| |
| #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); |
| } |
| #endif /* CONFIG_SMP */ |
| |
| static void init_rq_hrtick(struct rq *rq) |
| { |
| #ifdef CONFIG_SMP |
| rq->hrtick_csd_pending = 0; |
| |
| rq->hrtick_csd.flags = 0; |
| rq->hrtick_csd.func = __hrtick_start; |
| rq->hrtick_csd.info = rq; |
| #endif |
| |
| hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); |
| rq->hrtick_timer.function = hrtick; |
| } |
| #else /* CONFIG_SCHED_HRTICK */ |
| static inline void hrtick_clear(struct rq *rq) |
| { |
| } |
| |
| static inline void init_rq_hrtick(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 |
| |
| void 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. |
| * |
| * This cmpxchg() implies a full barrier, which pairs with the write |
| * barrier implied by the wakeup in wake_up_q(). |
| */ |
| if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL)) |
| return; |
| |
| get_task_struct(task); |
| |
| /* |
| * The head is context local, there can be no concurrency. |
| */ |
| *head->lastp = node; |
| head->lastp = &node->next; |
| } |
| |
| 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() implies a wmb() to pair 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; |
| |
| if (!raw_spin_trylock_irqsave(&rq->lock, flags)) |
| return; |
| 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(); |
| struct sched_domain *sd; |
| |
| if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu)) |
| return cpu; |
| |
| rcu_read_lock(); |
| for_each_domain(cpu, sd) { |
| for_each_cpu(i, sched_domain_span(sd)) { |
| if (cpu == i) |
| continue; |
| |
| if (!idle_cpu(i) && is_housekeeping_cpu(i)) { |
| cpu = i; |
| goto unlock; |
| } |
| } |
| } |
| |
| if (!is_housekeeping_cpu(cpu)) |
| cpu = housekeeping_any_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 inline bool got_nohz_idle_kick(void) |
| { |
| int cpu = smp_processor_id(); |
| |
| if (!test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu))) |
| return false; |
| |
| if (idle_cpu(cpu) && !need_resched()) |
| return true; |
| |
| /* |
| * We can't run Idle Load Balance on this CPU for this time so we |
| * cancel it and clear NOHZ_BALANCE_KICK |
| */ |
| clear_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu)); |
| return false; |
| } |
| |
| #else /* CONFIG_NO_HZ_COMMON */ |
| |
| static inline bool got_nohz_idle_kick(void) |
| { |
| return false; |
| } |
| |
| #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 */ |
| |
| void sched_avg_update(struct rq *rq) |
| { |
| s64 period = sched_avg_period(); |
| |
| while ((s64)(rq_clock(rq) - rq->age_stamp) > period) { |
| /* |
| * Inline assembly required to prevent the compiler |
| * optimising this loop into a divmod call. |
| * See __iter_div_u64_rem() for another example of this. |
| */ |
| asm("" : "+rm" (rq->age_stamp)); |
| rq->age_stamp += period; |
| rq->rt_avg /= 2; |
| } |
| } |
| |
| #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) |
| { |
| int prio = p->static_prio - MAX_RT_PRIO; |
| struct load_weight *load = &p->se.load; |
| |
| /* |
| * SCHED_IDLE tasks get minimal weight: |
| */ |
| if (idle_policy(p->policy)) { |
| load->weight = scale_load(WEIGHT_IDLEPRIO); |
| load->inv_weight = WMULT_IDLEPRIO; |
| return; |
| } |
| |
| load->weight = scale_load(sched_prio_to_weight[prio]); |
| load->inv_weight = sched_prio_to_wmult[prio]; |
| } |
| |
| 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); |
| |
| 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); |
| |
| p->sched_class->dequeue_task(rq, p, flags); |
| } |
| |
| void activate_task(struct rq *rq, struct task_struct *p, int flags) |
| { |
| if (task_contributes_to_load(p)) |
| rq->nr_uninterruptible--; |
| |
| enqueue_task(rq, p, flags); |
| } |
| |
| void deactivate_task(struct rq *rq, struct task_struct *p, int flags) |
| { |
| if (task_contributes_to_load(p)) |
| rq->nr_uninterruptible++; |
| |
| dequeue_task(rq, p, flags); |
| } |
| |
| /* |
| * __normal_prio - return the priority that is based on the static prio |
| */ |
| static inline int __normal_prio(struct task_struct *p) |
| { |
| return p->static_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) |
| { |
| int prio; |
| |
| if (task_has_dl_policy(p)) |
| prio = MAX_DL_PRIO-1; |
| else if (task_has_rt_policy(p)) |
| prio = MAX_RT_PRIO-1 - p->rt_priority; |
| else |
| prio = __normal_prio(p); |
| return 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) |
| { |
| const struct sched_class *class; |
| |
| if (p->sched_class == rq->curr->sched_class) { |
| rq->curr->sched_class->check_preempt_curr(rq, p, flags); |
| } else { |
| for_each_class(class) { |
| if (class == rq->curr->sched_class) |
| break; |
| if (class == p->sched_class) { |
| resched_curr(rq); |
| break; |
| } |
| } |
| } |
| |
| /* |
| * 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, true); |
| } |
| |
| #ifdef CONFIG_SMP |
| /* |
| * 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); |
| |
| p->on_rq = TASK_ON_RQ_MIGRATING; |
| dequeue_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); |
| enqueue_task(rq, p, 0); |
| p->on_rq = TASK_ON_RQ_QUEUED; |
| 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) |
| { |
| if (p->flags & PF_KTHREAD) { |
| if (unlikely(!cpu_online(dest_cpu))) |
| return rq; |
| } else { |
| if (unlikely(!cpu_active(dest_cpu))) |
| return rq; |
| } |
| |
| /* Affinity changed (again). */ |
| if (!cpumask_test_cpu(dest_cpu, &p->cpus_allowed)) |
| 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_allowed |
| * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test. |
| */ |
| sched_ttwu_pending(); |
| |
| 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_allowed, 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_curr_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_allowed, new_mask)) |
| goto out; |
| |
| if (!cpumask_intersects(new_mask, cpu_valid_mask)) { |
| 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; |
| |
| dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask); |
| 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); |
| tlb_migrate_finish(p->mm); |
| 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); |
| p->se.nr_migrations++; |
| perf_event_task_migrate(p); |
| } |
| |
| __set_task_cpu(p, new_cpu); |
| } |
| |
| 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); |
| |
| p->on_rq = TASK_ON_RQ_MIGRATING; |
| deactivate_task(src_rq, p, 0); |
| set_task_cpu(p, cpu); |
| activate_task(dst_rq, p, 0); |
| p->on_rq = TASK_ON_RQ_QUEUED; |
| 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_allowed)) |
| goto unlock; |
| |
| if (!cpumask_test_cpu(arg->src_cpu, &arg->dst_task->cpus_allowed)) |
| 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) |
| { |
| struct migration_swap_arg arg; |
| int ret = -EINVAL; |
| |
| arg = (struct migration_swap_arg){ |
| .src_task = cur, |
| .src_cpu = task_cpu(cur), |
| .dst_task = p, |
| .dst_cpu = task_cpu(p), |
| }; |
| |
| 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_allowed)) |
| goto out; |
| |
| if (!cpumask_test_cpu(arg.src_cpu, &arg.dst_task->cpus_allowed)) |
| 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; |
| } |
| |
| /* |
| * 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_allowed 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_allowed)) |
| return dest_cpu; |
| } |
| } |
| |
| for (;;) { |
| /* Any allowed, online CPU? */ |
| for_each_cpu(dest_cpu, &p->cpus_allowed) { |
| if (!(p->flags & PF_KTHREAD) && !cpu_active(dest_cpu)) |
| continue; |
| if (!cpu_online(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; |
| } |
| /* Fall-through */ |
| 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_allowed 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_allowed); |
| |
| /* |
| * 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_allowed |
| * 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(!cpumask_test_cpu(cpu, &p->cpus_allowed) || |
| !cpu_online(cpu))) |
| cpu = select_fallback_rq(task_cpu(p), p); |
| |
| return cpu; |
| } |
| |
| static void update_avg(u64 *avg, u64 sample) |
| { |
| s64 diff = sample - *avg; |
| *avg += diff >> 3; |
| } |
| |
| 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, ¶m); |
| |
| 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); |
| } |
| |
| static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags) |
| { |
| activate_task(rq, p, en_flags); |
| p->on_rq = TASK_ON_RQ_QUEUED; |
| |
| /* If a worker is waking up, notify the workqueue: */ |
| if (p->flags & PF_WQ_WORKER) |
| wq_worker_waking_up(p, cpu_of(rq)); |
| } |
| |
| /* |
| * 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); |
| |
| #ifdef CONFIG_SMP |
| if (p->sched_contributes_to_load) |
| rq->nr_uninterruptible--; |
| |
| if (wake_flags & WF_MIGRATED) |
| en_flags |= ENQUEUE_MIGRATED; |
| #endif |
| |
| ttwu_activate(rq, p, en_flags); |
| ttwu_do_wakeup(rq, p, wake_flags, rf); |
| } |
| |
| /* |
| * Called in case the task @p isn't fully descheduled from its runqueue, |
| * in this case we must do a remote wakeup. Its a 'light' wakeup though, |
| * since all we need to do is flip p->state to TASK_RUNNING, since |
| * the task is still ->on_rq. |
| */ |
| static int ttwu_remote(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) |
| { |
| struct rq *rq = this_rq(); |
| struct llist_node *llist = llist_del_all(&rq->wake_list); |
| struct task_struct *p, *t; |
| struct rq_flags rf; |
| |
| if (!llist) |
| return; |
| |
| rq_lock_irqsave(rq, &rf); |
| update_rq_clock(rq); |
| |
| llist_for_each_entry_safe(p, t, llist, wake_entry) |
| ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf); |
| |
| rq_unlock_irqrestore(rq, &rf); |
| } |
| |
| void scheduler_ipi(void) |
| { |
| /* |
| * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting |
| * TIF_NEED_RESCHED remotely (for the first time) will also send |
| * this IPI. |
| */ |
| preempt_fold_need_resched(); |
| |
| if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()) |
| return; |
| |
| /* |
| * Not all reschedule IPI handlers call irq_enter/irq_exit, since |
| * traditionally all their work was done from the interrupt return |
| * path. Now that we actually do some work, we need to make sure |
| * we do call them. |
| * |
| * Some archs already do call them, luckily irq_enter/exit nest |
| * properly. |
| * |
| * Arguably we should visit all archs and update all handlers, |
| * however a fair share of IPIs are still resched only so this would |
| * somewhat pessimize the simple resched case. |
| */ |
| irq_enter(); |
| sched_ttwu_pending(); |
| |
| /* |
| * Check if someone kicked us for doing the nohz idle load balance. |
| */ |
| if (unlikely(got_nohz_idle_kick())) { |
| this_rq()->idle_balance = 1; |
| raise_softirq_irqoff(SCHED_SOFTIRQ); |
| } |
| irq_exit(); |
| } |
| |
| static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags) |
| { |
| struct rq *rq = cpu_rq(cpu); |
| |
| p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); |
| |
| if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) { |
| if (!set_nr_if_polling(rq->idle)) |
| smp_send_reschedule(cpu); |
| else |
| trace_sched_wake_idle_without_ipi(cpu); |
| } |
| } |
| |
| 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) |
| { |
| return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu); |
| } |
| #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 defined(CONFIG_SMP) |
| if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) { |
| sched_clock_cpu(cpu); /* Sync clocks across CPUs */ |
| ttwu_queue_remote(p, cpu, wake_flags); |
| return; |
| } |
| #endif |
| |
| 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 |
| * |
| * Transitivity guarantees that B happens after A and C after B. |
| * Note: we only require RCpc transitivity. |
| * 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) |
| * 2) smp_cond_load_acquire(!X->on_cpu) |
| * |
| * 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 observe the state that lead to our wakeup. That is, not only must our |
| * task observe its own prior state, it must also observe the stores prior to |
| * its wakeup. |
| * |
| * This means that any means of doing remote wakeups must order the CPU doing |
| * the wakeup against the CPU the task is going to end up running on. This, |
| * however, is already required for the regular Program-Order guarantee above, |
| * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire). |
| * |
| */ |
| |
| /** |
| * 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_*) |
| * |
| * If (@state & @p->state) @p->state = TASK_RUNNING. |
| * |
| * If the task was not queued/runnable, also place it back on a runqueue. |
| * |
| * Atomic against schedule() which would dequeue a task, also see |
| * set_current_state(). |
| * |
| * 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; |
| |
| /* |
| * 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 mb() in |
| * set_current_state() the waiting thread does. |
| */ |
| raw_spin_lock_irqsave(&p->pi_lock, flags); |
| smp_mb__after_spinlock(); |
| if (!(p->state & state)) |
| goto out; |
| |
| trace_sched_waking(p); |
| |
| /* We're going to change ->state: */ |
| success = 1; |
| cpu = task_cpu(p); |
| |
| /* |
| * 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() |
| * [S] p->on_rq = 1; [L] P->state |
| * UNLOCK rq->lock -----. |
| * \ |
| * +--- RMB |
| * schedule() / |
| * LOCK rq->lock -----' |
| * UNLOCK rq->lock |
| * |
| * [task p] |
| * [S] p->state = UNINTERRUPTIBLE [L] p->on_rq |
| * |
| * Pairs with the UNLOCK+LOCK on rq->lock from the |
| * last wakeup of our task and the schedule that got our task |
| * current. |
| */ |
| smp_rmb(); |
| if (p->on_rq && ttwu_remote(p, wake_flags)) |
| goto stat; |
| |
| #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. |
| * |
| * [S] ->on_cpu = 1; [L] ->on_rq |
| * UNLOCK rq->lock |
| * RMB |
| * LOCK rq->lock |
| * [S] ->on_rq = 0; [L] ->on_cpu |
| * |
| * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock |
| * from the consecutive calls to schedule(); the first switching to our |
| * task, the second putting it to sleep. |
| */ |
| smp_rmb(); |
| |
| /* |
| * 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_lock_switch(). |
| * |
| * 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); |
| |
| p->sched_contributes_to_load = !!task_contributes_to_load(p); |
| p->state = TASK_WAKING; |
| |
| if (p->in_iowait) { |
| delayacct_blkio_end(); |
| atomic_dec(&task_rq(p)->nr_iowait); |
| } |
| |
| cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags); |
| if (task_cpu(p) != cpu) { |
| wake_flags |= WF_MIGRATED; |
| set_task_cpu(p, cpu); |
| } |
| |
| #else /* CONFIG_SMP */ |
| |
| if (p->in_iowait) { |
| delayacct_blkio_end(); |
| atomic_dec(&task_rq(p)->nr_iowait); |
| } |
| |
| #endif /* CONFIG_SMP */ |
| |
| ttwu_queue(p, cpu, wake_flags); |
| stat: |
| ttwu_stat(p, cpu, wake_flags); |
| out: |
| raw_spin_unlock_irqrestore(&p->pi_lock, flags); |
| |
| return success; |
| } |
| |
| /** |
| * try_to_wake_up_local - try to wake up a local task with rq lock held |
| * @p: the thread to be awakened |
| * @rf: request-queue flags for pinning |
| * |
| * Put @p on the run-queue if it's not already there. The caller must |
| * ensure that this_rq() is locked, @p is bound to this_rq() and not |
| * the current task. |
| */ |
| static void try_to_wake_up_local(struct task_struct *p, struct rq_flags *rf) |
| { |
| struct rq *rq = task_rq(p); |
| |
| if (WARN_ON_ONCE(rq != this_rq()) || |
| WARN_ON_ONCE(p == current)) |
| return; |
| |
| lockdep_assert_held(&rq->lock); |
| |
| if (!raw_spin_trylock(&p->pi_lock)) { |
| /* |
| * This is OK, because current is on_cpu, which avoids it being |
| * picked for load-balance and preemption/IRQs are still |
| * disabled avoiding further scheduler activity on it and we've |
| * not yet picked a replacement task. |
| */ |
| rq_unlock(rq, rf); |
| raw_spin_lock(&p->pi_lock); |
| rq_relock(rq, rf); |
| } |
| |
| if (!(p->state & TASK_NORMAL)) |
| goto out; |
| |
| trace_sched_waking(p); |
| |
| if (!task_on_rq_queued(p)) { |
| if (p->in_iowait) { |
| delayacct_blkio_end(); |
| atomic_dec(&rq->nr_iowait); |
| } |
| ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK); |
| } |
| |
| ttwu_do_wakeup(rq, p, 0, rf); |
| ttwu_stat(p, smp_processor_id(), 0); |
| out: |
| raw_spin_unlock(&p->pi_lock); |
| } |
| |
| /** |
| * 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. |
| * |
| * It may be assumed that this function implies a write memory barrier before |
| * changing the task state if and only if any tasks are woken up. |
| */ |
| 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_NUMA_BALANCING |
| if (p->mm && atomic_read(&p->mm->mm_users) == 1) { |
| p->mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay); |
| p->mm->numa_scan_seq = 0; |
| } |
| |
| if (clone_flags & CLONE_VM) |
| p->numa_preferred_nid = current->numa_preferred_nid; |
| else |
| p->numa_preferred_nid = -1; |
| |
| p->node_stamp = 0ULL; |
| p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0; |
| p->numa_scan_period = sysctl_numa_balancing_scan_delay; |
| p->numa_work.next = &p->numa_work; |
| p->numa_faults = NULL; |
| p->last_task_numa_placement = 0; |
| p->last_sum_exec_runtime = 0; |
| |
| p->numa_group = NULL; |
| #endif /* CONFIG_NUMA_BALANCING */ |
| } |
| |
| 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 __user *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 __user *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) |
| { |
| unsigned long flags; |
| int cpu = get_cpu(); |
| |
| __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; |
| |
| /* |
| * 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 = __normal_prio(p); |
| 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)) { |
| put_cpu(); |
| 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); |
| |
| /* |
| * The child is not yet in the pid-hash so no cgroup attach races, |
| * and the cgroup is pinned to this child due to cgroup_fork() |
| * is ran before sched_fork(). |
| * |
| * Silence PROVE_RCU. |
| */ |
| raw_spin_lock_irqsave(&p->pi_lock, flags); |
| /* |
| * We're setting the CPU for the first time, we don't migrate, |
| * so use __set_task_cpu(). |
| */ |
| __set_task_cpu(p, cpu); |
| if (p->sched_class->task_fork) |
| p->sched_class->task_fork(p); |
| raw_spin_unlock_irqrestore(&p->pi_lock, flags); |
| |
| #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 |
| |
| put_cpu(); |
| return 0; |
| } |
| |
| 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_allowed 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. |
| */ |
| __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->se); |
| |
| activate_task(rq, p, ENQUEUE_NOCLOCK); |
| p->on_rq = TASK_ON_RQ_QUEUED; |
| 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 struct static_key preempt_notifier_key = STATIC_KEY_INIT_FALSE; |
| |
| void preempt_notifier_inc(void) |
| { |
| static_key_slow_inc(&preempt_notifier_key); |
| } |
| EXPORT_SYMBOL_GPL(preempt_notifier_inc); |
| |
| void preempt_notifier_dec(void) |
| { |
| static_key_slow_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_key_false(&preempt_notifier_key)) |
| WARN(1, "registering preempt_notifier while notifiers disabled\n"); |
| |
| hlist_add_head(¬ifier->link, ¤t->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(¬ifier->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_key_false(&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_key_false(&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 */ |
| |
| /** |
| * 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) |
| { |
| sched_info_switch(rq, prev, next); |
| perf_event_task_sched_out(prev, next); |
| fire_sched_out_preempt_notifiers(prev, next); |
| prepare_lock_switch(rq, 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_lock_switch), 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); |
| /* |
| * The membarrier system call requires a full memory barrier |
| * after storing to rq->curr, before going back to user-space. |
| * |
| * TODO: This smp_mb__after_unlock_lock can go away if PPC end |
| * up adding a full barrier to switch_mm(), or we should figure |
| * out if a smp_mb__after_unlock_lock is really the proper API |
| * to use. |
| */ |
| smp_mb__after_unlock_lock(); |
| finish_lock_switch(rq, prev); |
| finish_arch_post_lock_switch(); |
| |
| fire_sched_in_preempt_notifiers(current); |
| if (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(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); |
| } |
| |
| /* |
| * 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) |
| { |
| struct mm_struct *mm, *oldmm; |
| |
| prepare_task_switch(rq, prev, next); |
| |
| mm = next->mm; |
| oldmm = prev->active_mm; |
| /* |
| * 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); |
| |
| if (!mm) { |
| next->active_mm = oldmm; |
| mmgrab(oldmm); |
| enter_lazy_tlb(oldmm, next); |
| } else |
| switch_mm_irqs_off(oldmm, mm, next); |
| |
| if (!prev->mm) { |
| prev->active_mm = NULL; |
| rq->prev_mm = oldmm; |
| } |
| |
| rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); |
| |
| /* |
| * 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, 1, _THIS_IP_); |
| |
| /* 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-preemptable 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; |
| } |
| |
| /* |
| * 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 += atomic_read(&cpu_rq(i)->nr_iowait); |
| |
| return sum; |
| } |
| |
| /* |
| * Consumers of these two interfaces, like for example the cpufreq menu |
| * governor are using nonsensical data. Boosting frequency 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) |
| { |
| struct rq *this = cpu_rq(cpu); |
| return atomic_read(&this->nr_iowait); |
| } |
| |
| void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) |
| { |
| struct rq *rq = this_rq(); |
| *nr_waiters = atomic_read(&rq->nr_iowait); |
| *load = rq->load.weight; |
| } |
| |
| #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 64bit 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; |
| |
| sched_clock_tick(); |
| |
| rq_lock(rq, &rf); |
| |
| update_rq_clock(rq); |
| curr->sched_class->task_tick(rq, curr, 0); |
| cpu_load_update_active(rq); |
| calc_global_load_tick(rq); |
| |
| rq_unlock(rq, &rf); |
| |
| perf_event_task_tick(); |
| |
| #ifdef CONFIG_SMP |
| rq->idle_balance = idle_cpu(cpu); |
| trigger_load_balance(rq); |
| #endif |
| rq_last_tick_reset(rq); |
| } |
| |
| #ifdef CONFIG_NO_HZ_FULL |
| /** |
| * scheduler_tick_max_deferment |
| * |
| * Keep at least one tick per second when a single |
| * active task is running because the scheduler doesn't |
| * yet completely support full dynticks environment. |
| * |
| * This makes sure that uptime, CFS vruntime, load |
| * balancing, etc... continue to move forward, even |
| * with a very low granularity. |
| * |
| * Return: Maximum deferment in nanoseconds. |
| */ |
| u64 scheduler_tick_max_deferment(void) |
| { |
| struct rq *rq = this_rq(); |
| unsigned long next, now = READ_ONCE(jiffies); |
| |
| next = rq->last_sched_tick + HZ; |
| |
| if (time_before_eq(next, now)) |
| return 0; |
| |
| return jiffies_to_nsecs(next - now); |
| } |
| #endif |
| |
| #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \ |
| defined(CONFIG_PREEMPT_TRACER)) |
| /* |
| * 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(preempt_disable_ip); |
| pr_cont("\n"); |
| } |
| if (panic_on_warn) |
| panic("scheduling while atomic\n"); |
| |
| 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) |
| { |
| #ifdef CONFIG_SCHED_STACK_END_CHECK |
| if (task_stack_end_corrupted(prev)) |
| panic("corrupted stack end detected inside scheduler\n"); |
| #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); |
| } |
| |
| /* |
| * 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 == &idle_sched_class || |
| prev->sched_class == &fair_sched_class) && |
| rq->nr_running == rq->cfs.h_nr_running)) { |
| |
| p = fair_sched_class.pick_next_task(rq, prev, rf); |
| if (unlikely(p == RETRY_TASK)) |
| goto again; |
| |
| /* Assumes fair_sched_class->next == idle_sched_class */ |
| if (unlikely(!p)) |
| p = idle_sched_class.pick_next_task(rq, prev, rf); |
| |
| return p; |
| } |
| |
| again: |
| for_each_class(class) { |
| p = class->pick_next_task(rq, prev, rf); |
| if (p) { |
| if (unlikely(p == RETRY_TASK)) |
| goto again; |
| 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_PREEMPT=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_PREEMPT 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; |
| struct rq_flags rf; |
| struct rq *rq; |
| int cpu; |
| |
| cpu = smp_processor_id(); |
| rq = cpu_rq(cpu); |
| prev = rq->curr; |
| |
| schedule_debug(prev); |
| |
| 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(). |
| */ |
| 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; |
| if (!preempt && prev->state) { |
| if (unlikely(signal_pending_state(prev->state, prev))) { |
| prev->state = TASK_RUNNING; |
| } else { |
| deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK); |
| prev->on_rq = 0; |
| |
| if (prev->in_iowait) { |
| atomic_inc(&rq->nr_iowait); |
| delayacct_blkio_start(); |
| } |
| |
| /* |
| * If a worker went to sleep, notify and ask workqueue |
| * whether it wants to wake up a task to maintain |
| * concurrency. |
| */ |
| if (prev->flags & PF_WQ_WORKER) { |
| struct task_struct *to_wakeup; |
| |
| to_wakeup = wq_worker_sleeping(prev); |
| if (to_wakeup) |
| try_to_wake_up_local(to_wakeup, &rf); |
| } |
| } |
| 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++; |
| 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. For TSO |
| * (e.g. x86), the architecture must provide its own |
| * barrier in switch_mm(). For weakly ordered machines |
| * for which spin_unlock() acts as a full memory |
| * barrier, finish_lock_switch() in common code takes |
| * care of this barrier. For weakly ordered machines for |
| * which spin_unlock() acts as a RELEASE barrier (only |
| * arm64 and PowerPC), arm64 has a full barrier in |
| * switch_to(), and PowerPC has |
| * smp_mb__after_unlock_lock() before |
| * finish_lock_switch(). |
| */ |
| ++*switch_count; |
| |
| 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) |
| { |
| /* |
| * The setting of TASK_RUNNING by try_to_wake_up() may be delayed |
| * when the following two conditions become true. |
| * - There is race condition of mmap_sem (It is acquired by |
| * exit_mm()), and |
| * - SMI occurs before setting TASK_RUNINNG. |
| * (or hypervisor of virtual machine switches to other guest) |
| * As a result, we may become TASK_RUNNING after becoming TASK_DEAD |
| * |
| * To avoid it, we have to wait for releasing tsk->pi_lock which |
| * is held by try_to_wake_up() |
| */ |
| raw_spin_lock_irq(¤t->pi_lock); |
| raw_spin_unlock_irq(¤t->pi_lock); |
| |
| /* Causes final put_task_struct in finish_task_switch(): */ |
| __set_current_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) |
| { |
| if (!tsk->state || 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); |
| } |
| |
| 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()); |
| } |
| 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 |
|