C++ preempt_enable_no_resched函数代码示例

/*
 * 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 __noreturn cpu_idle(void)
{
	int cpu;

	/* CPU is going idle. */
	cpu = smp_processor_id();

	/* endless idle loop with no priority at all */
	while (1) {
		tick_nohz_stop_sched_tick(1);
		while (!need_resched() && cpu_online(cpu)) {
#ifdef CONFIG_MIPS_MT_SMTC
			extern void smtc_idle_loop_hook(void);

			smtc_idle_loop_hook();
#endif
			if (cpu_wait)
				(*cpu_wait)();
		}
#ifdef CONFIG_HOTPLUG_CPU
		if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
		    (system_state == SYSTEM_RUNNING ||
		     system_state == SYSTEM_BOOTING))
			play_dead();
#endif
		tick_nohz_restart_sched_tick();
		preempt_enable_no_resched();
		schedule();
		preempt_disable();
	}
}

/*
 * 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();
        while (!need_resched()) {
            void (*idle)(void);

            if (__get_cpu_var(cpu_idle_state))
                __get_cpu_var(cpu_idle_state) = 0;

            check_pgt_cache();
            rmb();
            idle = pm_idle;

            if (!idle)
                idle = default_idle;

            if (cpu_is_offline(cpu))
                play_dead();

            __get_cpu_var(irq_stat).idle_timestamp = jiffies;
            idle();
        }
        tick_nohz_restart_sched_tick();
        preempt_enable_no_resched();
        schedule();
        preempt_disable();
    }
}

/*
 * 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();
		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();
	}
}

static void xen_restore_fl(unsigned long flags)
{
	struct vcpu_info *vcpu;

	/* convert from IF type flag */
	flags = !(flags & X86_EFLAGS_IF);

	/* There's a one instruction preempt window here.  We need to
	   make sure we're don't switch CPUs between getting the vcpu
	   pointer and updating the mask. */
	preempt_disable();
	vcpu = this_cpu_read(xen_vcpu);
	vcpu->evtchn_upcall_mask = flags;
	preempt_enable_no_resched();

	/* Doesn't matter if we get preempted here, because any
	   pending event will get dealt with anyway. */

	if (flags == 0) {
		preempt_check_resched();
		barrier(); /* unmask then check (avoid races) */
		if (unlikely(vcpu->evtchn_upcall_pending))
			xen_force_evtchn_callback();
	}
}

void cpu_idle(void)
{
	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();

			clear_thread_flag(TIF_POLLING_NRFLAG);

			local_irq_disable();
			/* Don't trace irqs off for idle */
			stop_critical_timings();
			if (!need_resched() && powersave != NULL)
				powersave();
			start_critical_timings();
			local_irq_enable();
			set_thread_flag(TIF_POLLING_NRFLAG);
		}

		rcu_idle_exit();
		tick_nohz_idle_exit();
		preempt_enable_no_resched();
		schedule();
		preempt_disable();
	}
}

/*
 * 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) {
		while (!need_resched()) {

			if (__get_cpu_var(cpu_idle_state))
				__get_cpu_var(cpu_idle_state) = 0;

			rmb();

			if (cpu_is_offline(cpu))
				play_dead();

			__get_cpu_var(irq_stat).idle_timestamp = jiffies;
			xen_idle();
		}
		preempt_enable_no_resched();
		schedule();
		preempt_disable();
	}
}

static void broadcast_tlb_mm_a15_erratum(struct mm_struct *mm)
{
	int cpu;
	cpumask_t mask = { CPU_BITS_NONE };

	if (!erratum_a15_798181())
		return;

	preempt_disable();
	dummy_flush_tlb_a15_erratum();
	for_each_online_cpu(cpu) {
		if (cpu == smp_processor_id())
			continue;
		/*
		 * We only need to send an IPI if the other CPUs are running
		 * the same mm (and ASID) as the one being invalidated. There
		 * is no need for locking around the current_mm check since
		 * the switch_mm() function has a dmb() for this erratum in
		 * case a context switch happens on another CPU after the
		 * condition below.
		 */
		if (mm == per_cpu(current_mm, cpu))
			cpumask_set_cpu(cpu, &mask);
	}
	smp_call_function_many(&mask, ipi_flush_tlb_a15_erratum, NULL, 1);
	preempt_enable_no_resched();
}

static void iseries_shared_idle(void)
{
	while (1) {
		tick_nohz_stop_sched_tick(1);
		while (!need_resched() && !hvlpevent_is_pending()) {
			local_irq_disable();
			ppc64_runlatch_off();

			/* Recheck with irqs off */
			if (!need_resched() && !hvlpevent_is_pending())
				yield_shared_processor();

			HMT_medium();
			local_irq_enable();
		}

		ppc64_runlatch_on();
		tick_nohz_restart_sched_tick();

		if (hvlpevent_is_pending())
			process_iSeries_events();

		preempt_enable_no_resched();
		schedule();
		preempt_disable();
	}
}

static void iseries_dedicated_idle(void)
{
	set_thread_flag(TIF_POLLING_NRFLAG);

	while (1) {
		tick_nohz_stop_sched_tick(1);
		if (!need_resched()) {
			while (!need_resched()) {
				ppc64_runlatch_off();
				HMT_low();

				if (hvlpevent_is_pending()) {
					HMT_medium();
					ppc64_runlatch_on();
					process_iSeries_events();
				}
			}

			HMT_medium();
		}

		ppc64_runlatch_on();
		tick_nohz_restart_sched_tick();
		preempt_enable_no_resched();
		schedule();
		preempt_disable();
	}
}

static int ksoftirqd(void * __bind_cpu)
{
	set_user_nice(current, 19);
	current->flags |= PF_NOFREEZE;

	set_current_state(TASK_INTERRUPTIBLE);

	while (!kthread_should_stop()) {
		preempt_disable();
		if (!local_softirq_pending()) {
			preempt_enable_no_resched();
			schedule();
			preempt_disable();
		}

		__set_current_state(TASK_RUNNING);

		while (local_softirq_pending()) {
			/* Preempt disable stops cpu going offline.
			   If already offline, we'll be on wrong CPU:
			   don't process */
			if (cpu_is_offline((long)__bind_cpu))
				goto wait_to_die;
			do_softirq();
			preempt_enable_no_resched();
			cond_resched();
			preempt_disable();
			rcu_qsctr_inc((long)__bind_cpu);
		}
		preempt_enable();
		set_current_state(TASK_INTERRUPTIBLE);
	}
	__set_current_state(TASK_RUNNING);
	return 0;

wait_to_die:
	preempt_enable();
	/* Wait for kthread_stop */
	set_current_state(TASK_INTERRUPTIBLE);
	while (!kthread_should_stop()) {
		schedule();
		set_current_state(TASK_INTERRUPTIBLE);
	}
	__set_current_state(TASK_RUNNING);
	return 0;
}

static void
restore_wp(
    const unsigned long 	cr0
)
{
    write_cr0( cr0 );
    preempt_enable_no_resched();
}

static inline void play_dead(void)
{
	idle_task_exit();
	local_irq_disable();
	cpu_clear(smp_processor_id(), cpu_initialized);
	preempt_enable_no_resched();
	HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
	cpu_bringup();
}

static void xen_irq_disable(void)
{
	/* There's a one instruction preempt window here.  We need to
	   make sure we're don't switch CPUs between getting the vcpu
	   pointer and updating the mask. */
	preempt_disable();
	this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
	preempt_enable_no_resched();
}

void raw_local_irq_disable(void)
{
	struct vcpu_info *_vcpu;

	preempt_disable();
	_vcpu = &HYPERVISOR_shared_info->vcpu_info[__vcpu_id];
	_vcpu->evtchn_upcall_mask = 1;
	preempt_enable_no_resched();
}

/*
 * 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)
{
	/* endless idle loop with no priority at all */
	while (1) {
		idle(); //default idle
		preempt_enable_no_resched();
		schedule();
		preempt_disable();
	}
}