| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * Generic entry points for the idle threads and |
| * implementation of the idle task scheduling class. |
| * |
| * (NOTE: these are not related to SCHED_IDLE batch scheduled |
| * tasks which are handled in sched/fair.c ) |
| */ |
| #include "sched.h" |
| |
| #include <trace/events/power.h> |
| |
| /* Linker adds these: start and end of __cpuidle functions */ |
| extern char __cpuidle_text_start[], __cpuidle_text_end[]; |
| |
| /** |
| * sched_idle_set_state - Record idle state for the current CPU. |
| * @idle_state: State to record. |
| */ |
| void sched_idle_set_state(struct cpuidle_state *idle_state) |
| { |
| idle_set_state(this_rq(), idle_state); |
| } |
| |
| static int __read_mostly cpu_idle_force_poll; |
| |
| void cpu_idle_poll_ctrl(bool enable) |
| { |
| if (enable) { |
| cpu_idle_force_poll++; |
| } else { |
| cpu_idle_force_poll--; |
| WARN_ON_ONCE(cpu_idle_force_poll < 0); |
| } |
| } |
| |
| #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP |
| static int __init cpu_idle_poll_setup(char *__unused) |
| { |
| cpu_idle_force_poll = 1; |
| |
| return 1; |
| } |
| __setup("nohlt", cpu_idle_poll_setup); |
| |
| static int __init cpu_idle_nopoll_setup(char *__unused) |
| { |
| cpu_idle_force_poll = 0; |
| |
| return 1; |
| } |
| __setup("hlt", cpu_idle_nopoll_setup); |
| #endif |
| |
| static noinline int __cpuidle cpu_idle_poll(void) |
| { |
| rcu_idle_enter(); |
| trace_cpu_idle_rcuidle(0, smp_processor_id()); |
| local_irq_enable(); |
| stop_critical_timings(); |
| |
| while (!tif_need_resched() && |
| (cpu_idle_force_poll || tick_check_broadcast_expired())) |
| cpu_relax(); |
| start_critical_timings(); |
| trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); |
| rcu_idle_exit(); |
| |
| return 1; |
| } |
| |
| /* Weak implementations for optional arch specific functions */ |
| void __weak arch_cpu_idle_prepare(void) { } |
| void __weak arch_cpu_idle_enter(void) { } |
| void __weak arch_cpu_idle_exit(void) { } |
| void __weak arch_cpu_idle_dead(void) { } |
| void __weak arch_cpu_idle(void) |
| { |
| cpu_idle_force_poll = 1; |
| local_irq_enable(); |
| } |
| |
| /** |
| * default_idle_call - Default CPU idle routine. |
| * |
| * To use when the cpuidle framework cannot be used. |
| */ |
| void __cpuidle default_idle_call(void) |
| { |
| if (current_clr_polling_and_test()) { |
| local_irq_enable(); |
| } else { |
| stop_critical_timings(); |
| arch_cpu_idle(); |
| start_critical_timings(); |
| } |
| } |
| |
| static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev, |
| int next_state) |
| { |
| /* |
| * The idle task must be scheduled, it is pointless to go to idle, just |
| * update no idle residency and return. |
| */ |
| if (current_clr_polling_and_test()) { |
| dev->last_residency = 0; |
| local_irq_enable(); |
| return -EBUSY; |
| } |
| |
| /* |
| * Enter the idle state previously returned by the governor decision. |
| * This function will block until an interrupt occurs and will take |
| * care of re-enabling the local interrupts |
| */ |
| return cpuidle_enter(drv, dev, next_state); |
| } |
| |
| /** |
| * cpuidle_idle_call - the main idle function |
| * |
| * NOTE: no locks or semaphores should be used here |
| * |
| * On archs that support TIF_POLLING_NRFLAG, is called with polling |
| * set, and it returns with polling set. If it ever stops polling, it |
| * must clear the polling bit. |
| */ |
| static void cpuidle_idle_call(void) |
| { |
| struct cpuidle_device *dev = cpuidle_get_device(); |
| struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); |
| int next_state, entered_state; |
| |
| /* |
| * Check if the idle task must be rescheduled. If it is the |
| * case, exit the function after re-enabling the local irq. |
| */ |
| if (need_resched()) { |
| local_irq_enable(); |
| return; |
| } |
| |
| /* |
| * The RCU framework needs to be told that we are entering an idle |
| * section, so no more rcu read side critical sections and one more |
| * step to the grace period |
| */ |
| |
| if (cpuidle_not_available(drv, dev)) { |
| tick_nohz_idle_stop_tick(); |
| rcu_idle_enter(); |
| |
| default_idle_call(); |
| goto exit_idle; |
| } |
| |
| /* |
| * Suspend-to-idle ("s2idle") is a system state in which all user space |
| * has been frozen, all I/O devices have been suspended and the only |
| * activity happens here and in iterrupts (if any). In that case bypass |
| * the cpuidle governor and go stratight for the deepest idle state |
| * available. Possibly also suspend the local tick and the entire |
| * timekeeping to prevent timer interrupts from kicking us out of idle |
| * until a proper wakeup interrupt happens. |
| */ |
| |
| if (idle_should_enter_s2idle() || dev->use_deepest_state) { |
| if (idle_should_enter_s2idle()) { |
| rcu_idle_enter(); |
| |
| entered_state = cpuidle_enter_s2idle(drv, dev); |
| if (entered_state > 0) { |
| local_irq_enable(); |
| goto exit_idle; |
| } |
| |
| rcu_idle_exit(); |
| } |
| |
| tick_nohz_idle_stop_tick(); |
| rcu_idle_enter(); |
| |
| next_state = cpuidle_find_deepest_state(drv, dev); |
| call_cpuidle(drv, dev, next_state); |
| } else { |
| bool stop_tick = true; |
| |
| /* |
| * Ask the cpuidle framework to choose a convenient idle state. |
| */ |
| next_state = cpuidle_select(drv, dev, &stop_tick); |
| |
| if (stop_tick || tick_nohz_tick_stopped()) |
| tick_nohz_idle_stop_tick(); |
| else |
| tick_nohz_idle_retain_tick(); |
| |
| rcu_idle_enter(); |
| |
| entered_state = call_cpuidle(drv, dev, next_state); |
| /* |
| * Give the governor an opportunity to reflect on the outcome |
| */ |
| cpuidle_reflect(dev, entered_state); |
| } |
| |
| exit_idle: |
| __current_set_polling(); |
| |
| /* |
| * It is up to the idle functions to reenable local interrupts |
| */ |
| if (WARN_ON_ONCE(irqs_disabled())) |
| local_irq_enable(); |
| |
| rcu_idle_exit(); |
| } |
| |
| /* |
| * Generic idle loop implementation |
| * |
| * Called with polling cleared. |
| */ |
| static void do_idle(void) |
| { |
| int cpu = smp_processor_id(); |
| /* |
| * If the arch has a polling bit, we maintain an invariant: |
| * |
| * Our polling bit is clear if we're not scheduled (i.e. if rq->curr != |
| * rq->idle). This means that, if rq->idle has the polling bit set, |
| * then setting need_resched is guaranteed to cause the CPU to |
| * reschedule. |
| */ |
| |
| __current_set_polling(); |
| tick_nohz_idle_enter(); |
| |
| while (!need_resched()) { |
| rmb(); |
| |
| local_irq_disable(); |
| |
| if (cpu_is_offline(cpu)) { |
| tick_nohz_idle_stop_tick(); |
| cpuhp_report_idle_dead(); |
| arch_cpu_idle_dead(); |
| } |
| |
| arch_cpu_idle_enter(); |
| |
| /* |
| * In poll mode we reenable interrupts and spin. Also if we |
| * detected in the wakeup from idle path that the tick |
| * broadcast device expired for us, we don't want to go deep |
| * idle as we know that the IPI is going to arrive right away. |
| */ |
| if (cpu_idle_force_poll || tick_check_broadcast_expired()) { |
| tick_nohz_idle_restart_tick(); |
| cpu_idle_poll(); |
| } else { |
| cpuidle_idle_call(); |
| } |
| arch_cpu_idle_exit(); |
| } |
| |
| /* |
| * Since we fell out of the loop above, we know TIF_NEED_RESCHED must |
| * be set, propagate it into PREEMPT_NEED_RESCHED. |
| * |
| * This is required because for polling idle loops we will not have had |
| * an IPI to fold the state for us. |
| */ |
| preempt_set_need_resched(); |
| tick_nohz_idle_exit(); |
| __current_clr_polling(); |
| |
| /* |
| * We promise to call sched_ttwu_pending() and reschedule if |
| * need_resched() is set while polling is set. That means that clearing |
| * polling needs to be visible before doing these things. |
| */ |
| smp_mb__after_atomic(); |
| |
| sched_ttwu_pending(); |
| schedule_idle(); |
| |
| if (unlikely(klp_patch_pending(current))) |
| klp_update_patch_state(current); |
| } |
| |
| bool cpu_in_idle(unsigned long pc) |
| { |
| return pc >= (unsigned long)__cpuidle_text_start && |
| pc < (unsigned long)__cpuidle_text_end; |
| } |
| |
| struct idle_timer { |
| struct hrtimer timer; |
| int done; |
| }; |
| |
| static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer) |
| { |
| struct idle_timer *it = container_of(timer, struct idle_timer, timer); |
| |
| WRITE_ONCE(it->done, 1); |
| set_tsk_need_resched(current); |
| |
| return HRTIMER_NORESTART; |
| } |
| |
| void play_idle(unsigned long duration_us) |
| { |
| struct idle_timer it; |
| |
| /* |
| * Only FIFO tasks can disable the tick since they don't need the forced |
| * preemption. |
| */ |
| WARN_ON_ONCE(current->policy != SCHED_FIFO); |
| WARN_ON_ONCE(current->nr_cpus_allowed != 1); |
| WARN_ON_ONCE(!(current->flags & PF_KTHREAD)); |
| WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY)); |
| WARN_ON_ONCE(!duration_us); |
| |
| rcu_sleep_check(); |
| preempt_disable(); |
| current->flags |= PF_IDLE; |
| cpuidle_use_deepest_state(true); |
| |
| it.done = 0; |
| hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); |
| it.timer.function = idle_inject_timer_fn; |
| hrtimer_start(&it.timer, ns_to_ktime(duration_us * NSEC_PER_USEC), |
| HRTIMER_MODE_REL_PINNED); |
| |
| while (!READ_ONCE(it.done)) |
| do_idle(); |
| |
| cpuidle_use_deepest_state(false); |
| current->flags &= ~PF_IDLE; |
| |
| preempt_fold_need_resched(); |
| preempt_enable(); |
| } |
| EXPORT_SYMBOL_GPL(play_idle); |
| |
| void cpu_startup_entry(enum cpuhp_state state) |
| { |
| arch_cpu_idle_prepare(); |
| cpuhp_online_idle(state); |
| while (1) |
| do_idle(); |
| } |
| |
| /* |
| * idle-task scheduling class. |
| */ |
| |
| #ifdef CONFIG_SMP |
| static int |
| select_task_rq_idle(struct task_struct *p, int cpu, int sd_flag, int flags) |
| { |
| return task_cpu(p); /* IDLE tasks as never migrated */ |
| } |
| |
| static int |
| balance_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) |
| { |
| return WARN_ON_ONCE(1); |
| } |
| #endif |
| |
| /* |
| * Idle tasks are unconditionally rescheduled: |
| */ |
| static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags) |
| { |
| resched_curr(rq); |
| } |
| |
| static void put_prev_task_idle(struct rq *rq, struct task_struct *prev) |
| { |
| } |
| |
| static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first) |
| { |
| update_idle_core(rq); |
| schedstat_inc(rq->sched_goidle); |
| } |
| |
| static struct task_struct * |
| pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) |
| { |
| struct task_struct *next = rq->idle; |
| |
| if (prev) |
| put_prev_task(rq, prev); |
| |
| set_next_task_idle(rq, next, true); |
| |
| return next; |
| } |
| |
| /* |
| * It is not legal to sleep in the idle task - print a warning |
| * message if some code attempts to do it: |
| */ |
| static void |
| dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags) |
| { |
| raw_spin_unlock_irq(&rq->lock); |
| printk(KERN_ERR "bad: scheduling from the idle thread!\n"); |
| dump_stack(); |
| raw_spin_lock_irq(&rq->lock); |
| } |
| |
| /* |
| * scheduler tick hitting a task of our scheduling class. |
| * |
| * NOTE: This function can be called remotely by the tick offload that |
| * goes along full dynticks. Therefore no local assumption can be made |
| * and everything must be accessed through the @rq and @curr passed in |
| * parameters. |
| */ |
| static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued) |
| { |
| } |
| |
| static void switched_to_idle(struct rq *rq, struct task_struct *p) |
| { |
| BUG(); |
| } |
| |
| static void |
| prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio) |
| { |
| BUG(); |
| } |
| |
| static unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task) |
| { |
| return 0; |
| } |
| |
| static void update_curr_idle(struct rq *rq) |
| { |
| } |
| |
| /* |
| * Simple, special scheduling class for the per-CPU idle tasks: |
| */ |
| const struct sched_class idle_sched_class = { |
| /* .next is NULL */ |
| /* no enqueue/yield_task for idle tasks */ |
| |
| /* dequeue is not valid, we print a debug message there: */ |
| .dequeue_task = dequeue_task_idle, |
| |
| .check_preempt_curr = check_preempt_curr_idle, |
| |
| .pick_next_task = pick_next_task_idle, |
| .put_prev_task = put_prev_task_idle, |
| .set_next_task = set_next_task_idle, |
| |
| #ifdef CONFIG_SMP |
| .balance = balance_idle, |
| .select_task_rq = select_task_rq_idle, |
| .set_cpus_allowed = set_cpus_allowed_common, |
| #endif |
| |
| .task_tick = task_tick_idle, |
| |
| .get_rr_interval = get_rr_interval_idle, |
| |
| .prio_changed = prio_changed_idle, |
| .switched_to = switched_to_idle, |
| .update_curr = update_curr_idle, |
| }; |