// 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 <linux/cpuidle.h>#include <linux/suspend.h>#include <linux/livepatch.h>#include "sched.h"#include "smp.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_SETUPstatic 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 /* CONFIG_GENERIC_IDLE_POLL_SETUP */ static noinline int __cpuidle cpu_idle_poll(void){	instrumentation_begin();	trace_cpu_idle(0, smp_processor_id());	stop_critical_timings();	ct_cpuidle_enter(); 	raw_local_irq_enable();	while (!tif_need_resched() &&	       (cpu_idle_force_poll || tick_check_broadcast_expired()))		cpu_relax();	raw_local_irq_disable(); 	ct_cpuidle_exit();	start_critical_timings();	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());	local_irq_enable();	instrumentation_end(); 	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 __noreturn arch_cpu_idle_dead(void) { while (1); }void __weak arch_cpu_idle(void){	cpu_idle_force_poll = 1;} #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST_IDLEDEFINE_STATIC_KEY_FALSE(arch_needs_tick_broadcast); static inline void cond_tick_broadcast_enter(void){	if (static_branch_unlikely(&arch_needs_tick_broadcast))		tick_broadcast_enter();} static inline void cond_tick_broadcast_exit(void){	if (static_branch_unlikely(&arch_needs_tick_broadcast))		tick_broadcast_exit();}#else /* !CONFIG_GENERIC_CLOCKEVENTS_BROADCAST_IDLE: */static inline void cond_tick_broadcast_enter(void) { }static inline void cond_tick_broadcast_exit(void) { }#endif /* !CONFIG_GENERIC_CLOCKEVENTS_BROADCAST_IDLE */ /** * default_idle_call - Default CPU idle routine. * * To use when the cpuidle framework cannot be used. */void __cpuidle default_idle_call(void){	instrumentation_begin();	if (!current_clr_polling_and_test()) {		cond_tick_broadcast_enter();		trace_cpu_idle(1, smp_processor_id());		stop_critical_timings(); 		ct_cpuidle_enter();		arch_cpu_idle();		ct_cpuidle_exit(); 		start_critical_timings();		trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());		cond_tick_broadcast_exit();	}	local_irq_enable();	instrumentation_end();} static int call_cpuidle_s2idle(struct cpuidle_driver *drv,			       struct cpuidle_device *dev,			       u64 max_latency_ns){	if (current_clr_polling_and_test())		return -EBUSY; 	return cpuidle_enter_s2idle(drv, dev, max_latency_ns);} 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_ns = 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);} static void idle_call_stop_or_retain_tick(bool stop_tick){	if (stop_tick || tick_nohz_tick_stopped())		tick_nohz_idle_stop_tick();	else		tick_nohz_idle_retain_tick();} /** * cpuidle_idle_call - the main idle function * * NOTE: no locks or semaphores should be used here * * On architectures 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(bool stop_tick){	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;	} 	if (cpuidle_not_available(drv, dev)) {		idle_call_stop_or_retain_tick(stop_tick); 		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 interrupts (if any). In that case bypass	 * the cpuidle governor and go straight 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->forced_idle_latency_limit_ns) {		u64 max_latency_ns; 		if (idle_should_enter_s2idle()) {			max_latency_ns = cpu_wakeup_latency_qos_limit() *					 NSEC_PER_USEC; 			entered_state = call_cpuidle_s2idle(drv, dev,							    max_latency_ns);			if (entered_state > 0)				goto exit_idle;		} else {			max_latency_ns = dev->forced_idle_latency_limit_ns;		} 		tick_nohz_idle_stop_tick(); 		next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns);		call_cpuidle(drv, dev, next_state);	} else if (drv->state_count > 1) {		/*		 * stop_tick is expected to be true by default by cpuidle		 * governors, which allows them to select idle states with		 * target residency above the tick period length.		 */		stop_tick = true; 		/*		 * Ask the cpuidle framework to choose a convenient idle state.		 */		next_state = cpuidle_select(drv, dev, &stop_tick); 		idle_call_stop_or_retain_tick(stop_tick); 		entered_state = call_cpuidle(drv, dev, next_state);		/*		 * Give the governor an opportunity to reflect on the outcome		 */		cpuidle_reflect(dev, entered_state);	} else {		idle_call_stop_or_retain_tick(stop_tick); 		/*		 * If there is only a single idle state (or none), there is		 * nothing meaningful for the governor to choose.  Skip the		 * governor and always use state 0.		 */		call_cpuidle(drv, dev, 0);	} exit_idle:	__current_set_polling(); 	/*	 * It is up to the idle functions to re-enable local interrupts	 */	if (WARN_ON_ONCE(irqs_disabled()))		local_irq_enable();} /* * Generic idle loop implementation * * Called with polling cleared. */static void do_idle(void){	int cpu = smp_processor_id();	bool got_tick = false; 	if (cpu_is_offline(cpu)) {		local_irq_disable();		/* All per-CPU kernel threads should be done by now. */		WARN_ON_ONCE(need_resched());		cpuhp_report_idle_dead();		arch_cpu_idle_dead();	} 	/*	 * Check if we need to update blocked load	 */	nohz_run_idle_balance(cpu); 	/*	 * 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()) { 		/*		 * Interrupts shouldn't be re-enabled from that point on until		 * the CPU sleeping instruction is reached. Otherwise an interrupt		 * may fire and queue a timer that would be ignored until the CPU		 * wakes from the sleeping instruction. And testing need_resched()		 * doesn't tell about pending needed timer reprogram.		 *		 * Several cases to consider:		 *		 * - SLEEP-UNTIL-PENDING-INTERRUPT based instructions such as		 *   "wfi" or "mwait" are fine because they can be entered with		 *   interrupt disabled.		 *		 * - sti;mwait() couple is fine because the interrupts are		 *   re-enabled only upon the execution of mwait, leaving no gap		 *   in-between.		 *		 * - ROLLBACK based idle handlers with the sleeping instruction		 *   called with interrupts enabled are NOT fine. In this scheme		 *   when the interrupt detects it has interrupted an idle handler,		 *   it rolls back to its beginning which performs the		 *   need_resched() check before re-executing the sleeping		 *   instruction. This can leak a pending needed timer reprogram.		 *   If such a scheme is really mandatory due to the lack of an		 *   appropriate CPU sleeping instruction, then a FAST-FORWARD		 *   must instead be applied: when the interrupt detects it has		 *   interrupted an idle handler, it must resume to the end of		 *   this idle handler so that the generic idle loop is iterated		 *   again to reprogram the tick.		 */		local_irq_disable(); 		arch_cpu_idle_enter();		rcu_nocb_flush_deferred_wakeup(); 		/*		 * In poll mode we re-enable 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(got_tick);		}		got_tick = tick_nohz_idle_got_tick();		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(); 	/*	 * RCU relies on this call to be done outside of an RCU read-side	 * critical section.	 */	flush_smp_call_function_queue();	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_precise(u64 duration_ns, u64 latency_ns){	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_ns);	WARN_ON_ONCE(current->mm); 	rcu_sleep_check();	preempt_disable();	current->flags |= PF_IDLE;	cpuidle_use_deepest_state(latency_ns); 	it.done = 0;	hrtimer_setup_on_stack(&it.timer, idle_inject_timer_fn, CLOCK_MONOTONIC,			       HRTIMER_MODE_REL_HARD);	hrtimer_start(&it.timer, ns_to_ktime(duration_ns),		      HRTIMER_MODE_REL_PINNED_HARD); 	while (!READ_ONCE(it.done))		do_idle(); 	cpuidle_use_deepest_state(0);	current->flags &= ~PF_IDLE; 	preempt_fold_need_resched();	preempt_enable();}EXPORT_SYMBOL_GPL(play_idle_precise); void cpu_startup_entry(enum cpuhp_state state){	current->flags |= PF_IDLE;	arch_cpu_idle_prepare();	cpuhp_online_idle(state);	while (1)		do_idle();} /* * idle-task scheduling class. */ static intselect_task_rq_idle(struct task_struct *p, int cpu, int flags){	return task_cpu(p); /* IDLE tasks as never migrated */} static intbalance_idle(struct rq *rq, struct rq_flags *rf){	return WARN_ON_ONCE(1);} /* * Idle tasks are unconditionally rescheduled: */static void wakeup_preempt_idle(struct rq *rq, struct task_struct *p, int flags){	resched_curr(rq);} static void update_curr_idle(struct rq *rq); static void put_prev_task_idle(struct rq *rq, struct task_struct *prev, struct task_struct *next){	update_curr_idle(rq);	scx_update_idle(rq, false, true);	update_rq_avg_idle(rq);} static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first){	update_idle_core(rq);	scx_update_idle(rq, true, true);	schedstat_inc(rq->sched_goidle);	next->se.exec_start = rq_clock_task(rq); 	/*	 * rq is about to be idle, check if we need to update the	 * lost_idle_time of clock_pelt	 */

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