自学教程：C++ start_critical_timings函数代码示例

/** * release_console_sem - unlock the console system * * Releases the semaphore which the caller holds on the console system * and the console driver list. * * While the semaphore was held, console output may have been buffered * by printk().  If this is the case, release_console_sem() emits * the output prior to releasing the semaphore. * * If there is output waiting for klogd, we wake it up. * * release_console_sem() may be called from any context. */void release_console_sem(void){	unsigned long flags;	unsigned _con_start, _log_end;	unsigned wake_klogd = 0;	if (console_suspended) {		up(&secondary_console_sem);		return;	}	console_may_schedule = 0;	for ( ; ; ) {		spin_lock_irqsave(&logbuf_lock, flags);		wake_klogd |= log_start - log_end;		if (con_start == log_end)			break;			/* Nothing to print */		_con_start = con_start;		_log_end = log_end;		con_start = log_end;		/* Flush */		spin_unlock(&logbuf_lock);		stop_critical_timings();	/* don't trace print latency */		call_console_drivers(_con_start, _log_end);		start_critical_timings();		local_irq_restore(flags);	}	console_locked = 0;	up(&console_sem);	spin_unlock_irqrestore(&logbuf_lock, flags);	if (wake_klogd)		wake_up_klogd();}

/* * The idle thread. There's no useful work to be * done, so just try to conserve power and have a * low exit latency (ie sit in a loop waiting for * somebody to say that they'd like to reschedule) */void cpu_idle(void){	int cpu = smp_processor_id();	current_thread_info()->status |= TS_POLLING;	/* endless idle loop with no priority at all */	while (1) {		tick_nohz_stop_sched_tick(1);		while (!need_resched()) {			check_pgt_cache();			rmb();			if (rcu_pending(cpu))				rcu_check_callbacks(cpu, 0);			if (cpu_is_offline(cpu))				play_dead();			local_irq_disable();			__get_cpu_var(irq_stat).idle_timestamp = jiffies;			/* Don't trace irqs off for idle */			stop_critical_timings();			pm_idle();			start_critical_timings();		}		tick_nohz_restart_sched_tick();		preempt_enable_no_resched();		schedule();		preempt_disable();	}}

/** * default_idle_call - Default CPU idle routine. * * To use when the cpuidle framework cannot be used. */void default_idle_call(void){	if (current_clr_polling_and_test()) {		local_irq_enable();	} else {		stop_critical_timings();		arch_cpu_idle();		start_critical_timings();	}}

static inline int 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;}

void cpu_idle(void){	if (ppc_md.idle_loop)		ppc_md.idle_loop();		set_thread_flag(TIF_POLLING_NRFLAG);	while (1) {		tick_nohz_idle_enter();		rcu_idle_enter();		while (!need_resched() && !cpu_should_die()) {			ppc64_runlatch_off();			if (ppc_md.power_save) {				clear_thread_flag(TIF_POLLING_NRFLAG);				smp_mb();				local_irq_disable();								stop_critical_timings();								if (!need_resched() && !cpu_should_die())					ppc_md.power_save();				start_critical_timings();				if (irqs_disabled())					local_irq_enable();				set_thread_flag(TIF_POLLING_NRFLAG);			} else {				HMT_low();				HMT_very_low();			}		}		HMT_medium();		ppc64_runlatch_on();		rcu_idle_exit();		tick_nohz_idle_exit();		if (cpu_should_die()) {			sched_preempt_enable_no_resched();			cpu_die();		}		schedule_preempt_disabled();	}}

static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx){		stop_critical_timings();	if (cx->entry_method == ACPI_CSTATE_FFH) {				acpi_processor_ffh_cstate_enter(cx);	} else if (cx->entry_method == ACPI_CSTATE_HALT) {		acpi_safe_halt();	} else {				inb(cx->address);		inl(acpi_gbl_FADT.xpm_timer_block.address);	}	start_critical_timings();}

/* * Generic idle loop implementation */static void cpu_idle_loop(void){	while (1) {		tick_nohz_idle_enter();		while (!need_resched()) {			check_pgt_cache();			rmb();			local_irq_disable();			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() ||			    __get_cpu_var(idle_force_poll)) {				cpu_idle_poll();			} else {				if (!current_clr_polling_and_test()) {					stop_critical_timings();					rcu_idle_enter();					arch_cpu_idle();					WARN_ON_ONCE(irqs_disabled());					rcu_idle_exit();					start_critical_timings();				} else {					local_irq_enable();				}				__current_set_polling();			}			arch_cpu_idle_exit();		}		tick_nohz_idle_exit();		schedule_preempt_disabled();		if (cpu_is_offline(smp_processor_id()))			arch_cpu_idle_dead();	}}

/* * The idle thread. There's no useful work to be * done, so just try to conserve power and have a * low exit latency (ie sit in a loop waiting for * somebody to say that they'd like to reschedule) */void cpu_idle(void){	int cpu = smp_processor_id();	/*	 * If we're the non-boot CPU, nothing set the stack canary up	 * for us.  CPU0 already has it initialized but no harm in	 * doing it again.  This is a good place for updating it, as	 * we wont ever return from this function (so the invalid	 * canaries already on the stack wont ever trigger).	 */	boot_init_stack_canary();	current_thread_info()->status |= TS_POLLING;	/* endless idle loop with no priority at all */	while (1) {		tick_nohz_stop_sched_tick(1);		while (!need_resched()) {			check_pgt_cache();			rmb();			if (cpu_is_offline(cpu))				play_dead();			local_irq_disable();			enter_idle();			/* Don't trace irqs off for idle */			stop_critical_timings();			pm_idle();			start_critical_timings();			/*			 * In many cases the interrupt that ended idle			 * has already called exit_idle. But some idle			 * loops can be woken up without interrupt.			 */			__exit_idle();		}		tick_nohz_restart_sched_tick();		preempt_enable_no_resched();		schedule();		preempt_disable();	}}

void default_idle(void){	if (likely(hlt_counter)) {		local_irq_disable();		stop_critical_timings();		cpu_relax();		start_critical_timings();		local_irq_enable();	} else {		clear_thread_flag(TIF_POLLING_NRFLAG);		smp_mb__after_clear_bit();		local_irq_disable();		while (!need_resched())			cpu_sleep();		local_irq_enable();		set_thread_flag(TIF_POLLING_NRFLAG);	}}

static void default_idle(void){	if (!hlt_counter) {		clear_thread_flag(TIF_POLLING_NRFLAG);		smp_mb__after_clear_bit();		set_bl_bit();		stop_critical_timings();		while (!need_resched())			cpu_sleep();		start_critical_timings();		clear_bl_bit();		set_thread_flag(TIF_POLLING_NRFLAG);	} else		while (!need_resched())			cpu_relax();}

/* * The idle thread, has rather strange semantics for calling pm_idle, * but this is what x86 does and we need to do the same, so that * things like cpuidle get called in the same way.  The only difference * is that we always respect 'hlt_counter' to prevent low power idle. */void cpu_idle(void){	local_fiq_enable();	/* endless idle loop with no priority at all */	while (1) {		idle_notifier_call_chain(IDLE_START);		tick_nohz_idle_enter();		rcu_idle_enter();		while (!need_resched()) {			/*			 * We need to disable interrupts here			 * to ensure we don't miss a wakeup call.			 */			local_irq_disable();#ifdef CONFIG_PL310_ERRATA_769419			wmb();#endif			if (hlt_counter) {				local_irq_enable();				cpu_relax();			} else if (!need_resched()) {				stop_critical_timings();				if (cpuidle_idle_call())					pm_idle();				start_critical_timings();				/*				 * pm_idle functions must always				 * return with IRQs enabled.				 */				WARN_ON(irqs_disabled());			} else				local_irq_enable();		}		rcu_idle_exit();		tick_nohz_idle_exit();		idle_notifier_call_chain(IDLE_END);		schedule_preempt_disabled();#ifdef CONFIG_HOTPLUG_CPU		if (cpu_is_offline(smp_processor_id()))			cpu_die();#endif	}}

/** * acpi_idle_do_entry - a helper function that does C2 and C3 type entry * @cx: cstate data * * Caller disables interrupt before call and enables interrupt after return. */static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx){	/* Don't trace irqs off for idle */	stop_critical_timings();	if (cx->entry_method == ACPI_CSTATE_FFH) {		/* Call into architectural FFH based C-state */		acpi_processor_ffh_cstate_enter(cx);	} else if (cx->entry_method == ACPI_CSTATE_HALT) {		acpi_safe_halt();	} else {		/* IO port based C-state */		inb(cx->address);		/* Dummy wait op - must do something useless after P_LVL2 read		   because chipsets cannot guarantee that STPCLK# signal		   gets asserted in time to freeze execution properly. */		inl(acpi_gbl_FADT.xpm_timer_block.address);	}	start_critical_timings();}

/* * The idle thread. There's no useful work to be done, so just try to conserve * power and have a low exit latency (ie sit in a loop waiting for somebody to * say that they'd like to reschedule) */void cpu_idle(void){	unsigned int cpu = smp_processor_id();	set_thread_flag(TIF_POLLING_NRFLAG);	/* endless idle loop with no priority at all */	while (1) {		tick_nohz_idle_enter();		rcu_idle_enter();		while (!need_resched()) {			check_pgt_cache();			rmb();			if (cpu_is_offline(cpu))				play_dead();			local_irq_disable();			/* Don't trace irqs off for idle */			stop_critical_timings();			if (cpuidle_idle_call())				sh_idle();			/*			 * Sanity check to ensure that sh_idle() returns			 * with IRQs enabled			 */			WARN_ON(irqs_disabled());			start_critical_timings();		}		rcu_idle_exit();		tick_nohz_idle_exit();		schedule_preempt_disabled();	}}

	/* avoid HT sibilings if possible */	if (cpumask_empty(tmp))		cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);	if (cpumask_empty(tmp)) {		mutex_unlock(&round_robin_lock);		return;	}	for_each_cpu(cpu, tmp) {		if (cpu_weight[cpu] < min_weight) {			min_weight = cpu_weight[cpu];			preferred_cpu = cpu;		}	}	if (tsk_in_cpu[tsk_index] != -1)		cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);	tsk_in_cpu[tsk_index] = preferred_cpu;	cpumask_set_cpu(preferred_cpu, pad_busy_cpus);	cpu_weight[preferred_cpu]++;	mutex_unlock(&round_robin_lock);	set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));}static void exit_round_robin(unsigned int tsk_index){	struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);	cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);	tsk_in_cpu[tsk_index] = -1;}static unsigned int idle_pct = 5; /* percentage */static unsigned int round_robin_time = 1; /* second */static int power_saving_thread(void *data){	struct sched_param param = {.sched_priority = 1};	int do_sleep;	unsigned int tsk_index = (unsigned long)data;	u64 last_jiffies = 0;	sched_setscheduler(current, SCHED_RR, &param);	set_freezable();	while (!kthread_should_stop()) {		int cpu;		u64 expire_time;		try_to_freeze();		/* round robin to cpus */		if (last_jiffies + round_robin_time * HZ < jiffies) {			last_jiffies = jiffies;			round_robin_cpu(tsk_index);		}		do_sleep = 0;		expire_time = jiffies + HZ * (100 - idle_pct) / 100;		while (!need_resched()) {			if (tsc_detected_unstable && !tsc_marked_unstable) {				/* TSC could halt in idle, so notify users */				mark_tsc_unstable("TSC halts in idle");				tsc_marked_unstable = 1;			}			if (lapic_detected_unstable && !lapic_marked_unstable) {				int i;				/* LAPIC could halt in idle, so notify users */				for_each_online_cpu(i)					clockevents_notify(						CLOCK_EVT_NOTIFY_BROADCAST_ON,						&i);				lapic_marked_unstable = 1;			}			local_irq_disable();			cpu = smp_processor_id();			if (lapic_marked_unstable)				clockevents_notify(					CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);			stop_critical_timings();			__monitor((void *)&current_thread_info()->flags, 0, 0);			smp_mb();			if (!need_resched())				__mwait(power_saving_mwait_eax, 1);			start_critical_timings();			if (lapic_marked_unstable)				clockevents_notify(					CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);			local_irq_enable();			if (jiffies > expire_time) {				do_sleep = 1;				break;			}		}		/*		 * current sched_rt has threshold for rt task running time.//.........这里部分代码省略.........

//.........这里部分代码省略.........	int next_state, entered_state;	bool broadcast;	/*	 * 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;	}	/*	 * During the idle period, stop measuring the disabled irqs	 * critical sections latencies	 */	stop_critical_timings();	/*	 * Tell the RCU framework we are entering an idle section,	 * so no more rcu read side critical sections and one more	 * step to the grace period	 */	rcu_idle_enter();	/*	 * Ask the cpuidle framework to choose a convenient idle state.	 * Fall back to the default arch idle method on errors.	 */	next_state = cpuidle_select(drv, dev);	if (next_state < 0) {use_default:		/*		 * We can't use the cpuidle framework, let's use the default		 * idle routine.		 */		if (current_clr_polling_and_test())			local_irq_enable();		else			arch_cpu_idle();		goto exit_idle;	}	/*	 * The idle task must be scheduled, it is pointless to	 * go to idle, just update no idle residency and get	 * out of this function	 */	if (current_clr_polling_and_test()) {		dev->last_residency = 0;		entered_state = next_state;		local_irq_enable();		goto exit_idle;	}	broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP);	/*	 * Tell the time framework to switch to a broadcast timer	 * because our local timer will be shutdown. If a local timer	 * is used from another cpu as a broadcast timer, this call may	 * fail if it is not available	 */	if (broadcast &&	    clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu))		goto use_default;	trace_cpu_idle_rcuidle(next_state, dev->cpu);	/*	 * 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	 */	entered_state = cpuidle_enter(drv, dev, next_state);	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);	if (broadcast)		clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);	/*	 * 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();	start_critical_timings();}

/** * 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 = __this_cpu_read(cpuidle_devices);	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;	}	/*	 * During the idle period, stop measuring the disabled irqs	 * critical sections latencies	 */	stop_critical_timings();	/*	 * Tell the RCU framework we are entering an idle section,	 * so no more rcu read side critical sections and one more	 * step to the grace period	 */	rcu_idle_enter();	/*	 * Check if the cpuidle framework is ready, otherwise fallback	 * to the default arch specific idle method	 */	next_state = cpuidle_select(drv, dev);	if (next_state < 0) {		default_idle_call();		goto exit_idle;	}	/*	 * The idle task must be scheduled, it is pointless to	 * go to idle, just update no idle residency and get	 * out of this function	 */	if (current_clr_polling_and_test()) {		dev->last_residency = 0;		entered_state = next_state;		local_irq_enable();		goto exit_idle;	}	/* Take note of the planned idle state. */	idle_set_state(this_rq(), &drv->states[next_state]);	/*	 * 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	 */	entered_state = cpuidle_enter(drv, dev, next_state);	/* The cpu is no longer idle or about to enter idle. */	idle_set_state(this_rq(), NULL);	if (entered_state == -EBUSY) {		default_idle_call();		goto exit_idle;	}	/*	 * 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();	start_critical_timings();}

static int clamp_thread(void *arg){	int cpunr = (unsigned long)arg;	DEFINE_TIMER(wakeup_timer, noop_timer, 0, 0);	static const struct sched_param param = {		.sched_priority = MAX_USER_RT_PRIO/2,	};	unsigned int count = 0;	unsigned int target_ratio;	set_bit(cpunr, cpu_clamping_mask);	set_freezable();	init_timer_on_stack(&wakeup_timer);	sched_setscheduler(current, SCHED_FIFO, &param);	while (true == clamping && !kthread_should_stop() &&		cpu_online(cpunr)) {		int sleeptime;		unsigned long target_jiffies;		unsigned int guard;		unsigned int compensated_ratio;		int interval; /* jiffies to sleep for each attempt */		unsigned int duration_jiffies = msecs_to_jiffies(duration);		unsigned int window_size_now;		try_to_freeze();		/*		 * make sure user selected ratio does not take effect until		 * the next round. adjust target_ratio if user has changed		 * target such that we can converge quickly.		 */		target_ratio = set_target_ratio;		guard = 1 + target_ratio/20;		window_size_now = window_size;		count++;		/*		 * systems may have different ability to enter package level		 * c-states, thus we need to compensate the injected idle ratio		 * to achieve the actual target reported by the HW.		 */		compensated_ratio = target_ratio +			get_compensation(target_ratio);		if (compensated_ratio <= 0)			compensated_ratio = 1;		interval = duration_jiffies * 100 / compensated_ratio;		/* align idle time */		target_jiffies = roundup(jiffies, interval);		sleeptime = target_jiffies - jiffies;		if (sleeptime <= 0)			sleeptime = 1;		schedule_timeout_interruptible(sleeptime);		/*		 * only elected controlling cpu can collect stats and update		 * control parameters.		 */		if (cpunr == control_cpu && !(count%window_size_now)) {			should_skip =				powerclamp_adjust_controls(target_ratio,							guard, window_size_now);			smp_mb();		}		if (should_skip)			continue;		target_jiffies = jiffies + duration_jiffies;		mod_timer(&wakeup_timer, target_jiffies);		if (unlikely(local_softirq_pending()))			continue;		/*		 * stop tick sched during idle time, interrupts are still		 * allowed. thus jiffies are updated properly.		 */		preempt_disable();		/* mwait until target jiffies is reached */		while (time_before(jiffies, target_jiffies)) {			unsigned long ecx = 1;			unsigned long eax = target_mwait;			/*			 * REVISIT: may call enter_idle() to notify drivers who			 * can save power during cpu idle. same for exit_idle()			 */			local_touch_nmi();			stop_critical_timings();			mwait_idle_with_hints(eax, ecx);			start_critical_timings();			atomic_inc(&idle_wakeup_counter);		}		preempt_enable();	}	del_timer_sync(&wakeup_timer);	clear_bit(cpunr, cpu_clamping_mask);	return 0;}/*//.........这里部分代码省略.........

	/* avoid HT sibilings if possible */	if (cpumask_empty(tmp))		cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);	if (cpumask_empty(tmp)) {		mutex_unlock(&round_robin_lock);		return;	}	for_each_cpu(cpu, tmp) {		if (cpu_weight[cpu] < min_weight) {			min_weight = cpu_weight[cpu];			preferred_cpu = cpu;		}	}	if (tsk_in_cpu[tsk_index] != -1)		cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);	tsk_in_cpu[tsk_index] = preferred_cpu;	cpumask_set_cpu(preferred_cpu, pad_busy_cpus);	cpu_weight[preferred_cpu]++;	mutex_unlock(&round_robin_lock);	set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));}static void exit_round_robin(unsigned int tsk_index){	struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);	cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);	tsk_in_cpu[tsk_index] = -1;}static unsigned int idle_pct = 5; /* percentage */static unsigned int round_robin_time = 1; /* second */static int power_saving_thread(void *data){	struct sched_param param = {.sched_priority = 1};	int do_sleep;	unsigned int tsk_index = (unsigned long)data;	u64 last_jiffies = 0;	sched_setscheduler(current, SCHED_RR, &param);	while (!kthread_should_stop()) {		unsigned long expire_time;		try_to_freeze();		/* round robin to cpus */		expire_time = last_jiffies + round_robin_time * HZ;		if (time_before(expire_time, jiffies)) {			last_jiffies = jiffies;			round_robin_cpu(tsk_index);		}		do_sleep = 0;		expire_time = jiffies + HZ * (100 - idle_pct) / 100;		while (!need_resched()) {			if (tsc_detected_unstable && !tsc_marked_unstable) {				/* TSC could halt in idle, so notify users */				mark_tsc_unstable("TSC halts in idle");				tsc_marked_unstable = 1;			}			local_irq_disable();			tick_broadcast_enable();			tick_broadcast_enter();			stop_critical_timings();			mwait_idle_with_hints(power_saving_mwait_eax, 1);			start_critical_timings();			tick_broadcast_exit();			local_irq_enable();			if (time_before(expire_time, jiffies)) {				do_sleep = 1;				break;			}		}		/*		 * current sched_rt has threshold for rt task running time.		 * When a rt task uses 95% CPU time, the rt thread will be		 * scheduled out for 5% CPU time to not starve other tasks. But		 * the mechanism only works when all CPUs have RT task running,		 * as if one CPU hasn't RT task, RT task from other CPUs will		 * borrow CPU time from this CPU and cause RT task use > 95%		 * CPU time. To make 'avoid starvation' work, takes a nap here.		 */		if (unlikely(do_sleep))			schedule_timeout_killable(HZ * idle_pct / 100);		/* If an external event has set the need_resched flag, then		 * we need to deal with it, or this loop will continue to		 * spin without calling __mwait().		 */		if (unlikely(need_resched()))			schedule();	}//.........这里部分代码省略.........

//.........这里部分代码省略.........	/*	 * Suspend-to-idle ("freeze") 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_freeze()) {		entered_state = cpuidle_enter_freeze(drv, dev);		if (entered_state >= 0) {			local_irq_enable();			goto exit_idle;		}		reflect = false;		next_state = cpuidle_find_deepest_state(drv, dev);	} else {		reflect = true;		/*		 * Ask the cpuidle framework to choose a convenient idle state.		 */		next_state = cpuidle_select(drv, dev);	}	/* Fall back to the default arch idle method on errors. */	if (next_state < 0)		goto use_default;	/*	 * The idle task must be scheduled, it is pointless to	 * go to idle, just update no idle residency and get	 * out of this function	 */	if (current_clr_polling_and_test()) {		dev->last_residency = 0;		entered_state = next_state;		local_irq_enable();		goto exit_idle;	}	broadcast = drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP;	/*	 * Tell the time framework to switch to a broadcast timer	 * because our local timer will be shutdown. If a local timer	 * is used from another cpu as a broadcast timer, this call may	 * fail if it is not available	 */	if (broadcast && tick_broadcast_enter())		goto use_default;	/* Take note of the planned idle state. */	idle_set_state(this_rq(), &drv->states[next_state]);	/*	 * 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	 */	entered_state = cpuidle_enter(drv, dev, next_state);	/* The cpu is no longer idle or about to enter idle. */	idle_set_state(this_rq(), NULL);	if (broadcast)		tick_broadcast_exit();	/*	 * Give the governor an opportunity to reflect on the outcome	 */	if (reflect)		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();	start_critical_timings();	return;use_default:	/*	 * We can't use the cpuidle framework, let's use the default	 * idle routine.	 */	if (current_clr_polling_and_test())		local_irq_enable();	else		arch_cpu_idle();	goto exit_idle;}

	/* avoid HT sibilings if possible */	if (cpumask_empty(tmp))		cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);	if (cpumask_empty(tmp)) {		mutex_unlock(&isolated_cpus_lock);		return;	}	for_each_cpu(cpu, tmp) {		if (cpu_weight[cpu] < min_weight) {			min_weight = cpu_weight[cpu];			preferred_cpu = cpu;		}	}	if (tsk_in_cpu[tsk_index] != -1)		cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);	tsk_in_cpu[tsk_index] = preferred_cpu;	cpumask_set_cpu(preferred_cpu, pad_busy_cpus);	cpu_weight[preferred_cpu]++;	mutex_unlock(&isolated_cpus_lock);	set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));}static void exit_round_robin(unsigned int tsk_index){	struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);	cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);	tsk_in_cpu[tsk_index] = -1;}static unsigned int idle_pct = 5; /* percentage */static unsigned int round_robin_time = 10; /* second */static int power_saving_thread(void *data){	struct sched_param param = {.sched_priority = 1};	int do_sleep;	unsigned int tsk_index = (unsigned long)data;	u64 last_jiffies = 0;	sched_setscheduler(current, SCHED_RR, &param);	while (!kthread_should_stop()) {		int cpu;		u64 expire_time;		try_to_freeze();		/* round robin to cpus */		if (last_jiffies + round_robin_time * HZ < jiffies) {			last_jiffies = jiffies;			round_robin_cpu(tsk_index);		}		do_sleep = 0;		current_thread_info()->status &= ~TS_POLLING;		/*		 * TS_POLLING-cleared state must be visible before we test		 * NEED_RESCHED:		 */		smp_mb();		expire_time = jiffies + HZ * (100 - idle_pct) / 100;		while (!need_resched()) {			local_irq_disable();			cpu = smp_processor_id();			clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER,				&cpu);			stop_critical_timings();			__monitor((void *)&current_thread_info()->flags, 0, 0);			smp_mb();			if (!need_resched())				__mwait(power_saving_mwait_eax, 1);			start_critical_timings();			clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT,				&cpu);			local_irq_enable();			if (jiffies > expire_time) {				do_sleep = 1;				break;			}		}		current_thread_info()->status |= TS_POLLING;		/*		 * current sched_rt has threshold for rt task running time.		 * When a rt task uses 95% CPU time, the rt thread will be		 * scheduled out for 5% CPU time to not starve other tasks. But		 * the mechanism only works when all CPUs have RT task running,		 * as if one CPU hasn't RT task, RT task from other CPUs will		 * borrow CPU time from this CPU and cause RT task use > 95%		 * CPU time. To make 'avoid starvation' work, takes a nap here.		 */		if (do_sleep)//.........这里部分代码省略.........