C++ idle_task函数代码示例

static int __cpuinit xen_cpu_up(unsigned int cpu)
{
	struct task_struct *idle = idle_task(cpu);
	int rc;

#ifdef CONFIG_X86_64
	/* Allocate node local memory for AP pdas */
	WARN_ON(cpu == 0);
	if (cpu > 0) {
		rc = get_local_pda(cpu);
		if (rc)
			return rc;
	}
#endif

#ifdef CONFIG_X86_32
	init_gdt(cpu);
	per_cpu(current_task, cpu) = idle;
	irq_ctx_init(cpu);
#else
	cpu_pda(cpu)->pcurrent = idle;
	clear_tsk_thread_flag(idle, TIF_FORK);
#endif
	xen_setup_timer(cpu);
	xen_init_lock_cpu(cpu);

	per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;

	/* make sure interrupts start blocked */
	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;

	rc = cpu_initialize_context(cpu, idle);
	if (rc)
		return rc;

	if (num_online_cpus() == 1)
		alternatives_smp_switch(1);

	rc = xen_smp_intr_init(cpu);
	if (rc)
		return rc;

	rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
	BUG_ON(rc);

	while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
		HYPERVISOR_sched_op(SCHEDOP_yield, 0);
		barrier();
	}

	return 0;
}

s32 os_main(u32 sp)
{
    struct __os_task__ *ptask;

    int_init();
    uart_init();
    dram_init();
    timer_init();
    mmc_init();

    PRINT_INFO("%s\n", sys_banner);

    coretimer_init();
    task_init();
    semaphore_init();

    PRINT_INFO("cpu_mode: %s; lr: 0x%x; sp: 0x%x; cpsr: 0x%x\n",
            get_cpu_mode(NULL), __get_lr(), sp, __get_cpsr());

    gpio_set_function(GPIO_16, OUTPUT);
    gpio_set_output(GPIO_16, 0);

    /* set_log_level(LOG_DEBUG); */

    /* create idle task */
    if ((ptask = tcb_alloc()) == NULL) {
        panic();
    }

    tcb_init(ptask, idle_task, 0, 256);

    /*os_ready_insert(ptask);*/

    current_task = &tcb[IDLE_TASK_ID];  /* assume that this is idle_task */

    /* create main task */
    if ((ptask = tcb_alloc()) == NULL) {
        panic();
    }

    tcb_init(ptask, main_task, 0, 100);

    os_ready_insert(ptask);

    /* 'slip into idle task', cause the os_main() is not a task (it's the god code of system) */
    __set_sp(&(task_stack[0][TASK_STK_SIZE]));
    current_task->state = TASK_RUNNING;
    idle_task(0);

    kassert(0);
    return 0;
}

static int __cpuinit xen_cpu_up(unsigned int cpu)
{
	struct task_struct *idle = idle_task(cpu);
	int rc;

	per_cpu(current_task, cpu) = idle;
#ifdef CONFIG_X86_32
	irq_ctx_init(cpu);
#else
	clear_tsk_thread_flag(idle, TIF_FORK);
	per_cpu(kernel_stack, cpu) =
		(unsigned long)task_stack_page(idle) -
		KERNEL_STACK_OFFSET + THREAD_SIZE;
	per_cpu(kernel_stack8k, cpu) =
		(unsigned long)task_stack_page(idle) -
		KERNEL_STACK_OFFSET + THREAD_SIZE - 8192;
#endif
	xen_setup_runstate_info(cpu);
	xen_setup_timer(cpu);
	xen_init_lock_cpu(cpu);

	per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;

	/* make sure interrupts start blocked */
	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;

	rc = cpu_initialize_context(cpu, idle);
	if (rc)
		return rc;

	if (num_online_cpus() == 1)
		alternatives_smp_switch(1);

	rc = xen_smp_intr_init(cpu);
	if (rc)
		return rc;

	rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
	BUG_ON(rc);

	while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
		HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
		barrier();
	}

	return 0;
}

static void do_stolen_accounting(void)
{
	struct vcpu_runstate_info state;
	struct vcpu_runstate_info *snap;
	s64 blocked, runnable, offline, stolen;
	cputime_t ticks;

	get_runstate_snapshot(&state);

	WARN_ON(state.state != RUNSTATE_running);

	snap = &__get_cpu_var(runstate_snapshot);

	/* work out how much time the VCPU has not been runn*ing*  */
	blocked = state.time[RUNSTATE_blocked] - snap->time[RUNSTATE_blocked];
	runnable = state.time[RUNSTATE_runnable] - snap->time[RUNSTATE_runnable];
	offline = state.time[RUNSTATE_offline] - snap->time[RUNSTATE_offline];

	*snap = state;

	/* Add the appropriate number of ticks of stolen time,
	   including any left-overs from last time.  Passing NULL to
	   account_steal_time accounts the time as stolen. */
	stolen = runnable + offline + __get_cpu_var(residual_stolen);

	if (stolen < 0)
		stolen = 0;

	ticks = iter_div_u64_rem(stolen, NS_PER_TICK, &stolen);
	__get_cpu_var(residual_stolen) = stolen;
	account_steal_time(NULL, ticks);

	/* Add the appropriate number of ticks of blocked time,
	   including any left-overs from last time.  Passing idle to
	   account_steal_time accounts the time as idle/wait. */
	blocked += __get_cpu_var(residual_blocked);

	if (blocked < 0)
		blocked = 0;

	ticks = iter_div_u64_rem(blocked, NS_PER_TICK, &blocked);
	__get_cpu_var(residual_blocked) = blocked;
	account_steal_time(idle_task(smp_processor_id()), ticks);
}

/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcu/tree.c. */
static void rcu_idle_exit_common(long long oldval)
{
	if (oldval) {
		RCU_TRACE(trace_rcu_dyntick(TPS("++="),
					    oldval, rcu_dynticks_nesting));
		return;
	}
	RCU_TRACE(trace_rcu_dyntick(TPS("End"), oldval, rcu_dynticks_nesting));
	if (IS_ENABLED(CONFIG_RCU_TRACE) && !is_idle_task(current)) {
		struct task_struct *idle __maybe_unused = idle_task(smp_processor_id());

		RCU_TRACE(trace_rcu_dyntick(TPS("Exit error: not idle task"),
			  oldval, rcu_dynticks_nesting));
		ftrace_dump(DUMP_ALL);
		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
			  current->pid, current->comm,
			  idle->pid, idle->comm); /* must be idle task! */
	}
}

/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
static void rcu_idle_exit_common(long long oldval)
{
	if (oldval) {
		RCU_TRACE(trace_rcu_dyntick("++=",
					    oldval, rcu_dynticks_nesting));
		return;
	}
	RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
	if (!is_idle_task(current)) {
		struct task_struct *idle = idle_task(smp_processor_id());

		RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
			  oldval, rcu_dynticks_nesting));
		ftrace_dump(DUMP_ALL);
		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
			  current->pid, current->comm,
			  idle->pid, idle->comm); /* must be idle task! */
	}
}

int __cpuinit xen_cpu_up(unsigned int cpu)
{
	struct task_struct *idle = idle_task(cpu);
	int rc;

#if 0
	rc = cpu_up_check(cpu);
	if (rc)
		return rc;
#endif

	init_gdt(cpu);
	per_cpu(current_task, cpu) = idle;
	irq_ctx_init(cpu);
	xen_setup_timer(cpu);

	/* make sure interrupts start blocked */
	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;

	rc = cpu_initialize_context(cpu, idle);
	if (rc)
		return rc;

	if (num_online_cpus() == 1)
		alternatives_smp_switch(1);

	rc = xen_smp_intr_init(cpu);
	if (rc)
		return rc;

	smp_store_cpu_info(cpu);
	set_cpu_sibling_map(cpu);
	/* This must be done before setting cpu_online_map */
	wmb();

	cpu_set(cpu, cpu_online_map);

	rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
	BUG_ON(rc);

	return 0;
}

/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
static void rcu_idle_enter_common(long long oldval)
{
	if (rcu_dynticks_nesting) {
		RCU_TRACE(trace_rcu_dyntick("--=",
					    oldval, rcu_dynticks_nesting));
		return;
	}
	RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
	if (!is_idle_task(current)) {
		struct task_struct *idle = idle_task(smp_processor_id());

		RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
					    oldval, rcu_dynticks_nesting));
		ftrace_dump(DUMP_ALL);
		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
			  current->pid, current->comm,
			  idle->pid, idle->comm); /* must be idle task! */
	}
	rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
}

static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
{
	smp_mb__before_atomic_inc();  
	atomic_inc(&rdtp->dynticks);
	
	smp_mb__after_atomic_inc();  
	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
	rcu_cleanup_after_idle(smp_processor_id());
	trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
	if (!is_idle_task(current)) {
		struct task_struct *idle = idle_task(smp_processor_id());

		trace_rcu_dyntick("Error on exit: not idle task",
				  oldval, rdtp->dynticks_nesting);
		ftrace_dump(DUMP_ALL);
		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
			  current->pid, current->comm,
			  idle->pid, idle->comm); 
	}
}

static struct task_struct *getthread(struct pt_regs *regs, int tid)
{
	/*
	 * Non-positive TIDs are remapped to the cpu shadow information
	 */
	if (tid == 0 || tid == -1)
		tid = -atomic_read(&kgdb_active) - 2;
	if (tid < 0) {
		if (kgdb_info[-tid - 2].task)
			return kgdb_info[-tid - 2].task;
		else
			return idle_task(-tid - 2);
	}

	/*
	 * find_task_by_pid_ns() does not take the tasklist lock anymore
	 * but is nicely RCU locked - hence is a pretty resilient
	 * thing to use:
	 */
	return find_task_by_pid_ns(tid, &init_pid_ns);
}

/*
 * Account time for a transition between system, hard irq or soft irq state.
 * Note that this function is called with interrupts enabled.
 */
void account_system_vtime(struct task_struct *tsk)
{
    struct thread_info *ti = task_thread_info(tsk);
    unsigned long flags;
    cputime_t delta_stime;
    __u64 now;

    local_irq_save(flags);

    now = ia64_get_itc();

    delta_stime = cycle_to_cputime(ti->ac_stime + (now - ti->ac_stamp));
    if (irq_count() || idle_task(smp_processor_id()) != tsk)
        account_system_time(tsk, 0, delta_stime, delta_stime);
    else
        account_idle_time(delta_stime);
    ti->ac_stime = 0;

    ti->ac_stamp = now;

    local_irq_restore(flags);
}

/*
 * Called from the context switch with interrupts disabled, to charge all
 * accumulated times to the current process, and to prepare accounting on
 * the next process.
 */
void ia64_account_on_switch(struct task_struct *prev, struct task_struct *next)
{
    struct thread_info *pi = task_thread_info(prev);
    struct thread_info *ni = task_thread_info(next);
    cputime_t delta_stime, delta_utime;
    __u64 now;

    now = ia64_get_itc();

    delta_stime = cycle_to_cputime(pi->ac_stime + (now - pi->ac_stamp));
    if (idle_task(smp_processor_id()) != prev)
        account_system_time(prev, 0, delta_stime, delta_stime);
    else
        account_idle_time(delta_stime);

    if (pi->ac_utime) {
        delta_utime = cycle_to_cputime(pi->ac_utime);
        account_user_time(prev, delta_utime, delta_utime);
    }

    pi->ac_stamp = ni->ac_stamp = now;
    ni->ac_stime = ni->ac_utime = 0;
}

/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcu/tree.c. */
static void rcu_idle_enter_common(long long newval)
{
	if (newval) {
		RCU_TRACE(trace_rcu_dyntick(TPS("--="),
					    rcu_dynticks_nesting, newval));
		rcu_dynticks_nesting = newval;
		return;
	}
	RCU_TRACE(trace_rcu_dyntick(TPS("Start"),
				    rcu_dynticks_nesting, newval));
	if (IS_ENABLED(CONFIG_RCU_TRACE) && !is_idle_task(current)) {
		struct task_struct *idle __maybe_unused = idle_task(smp_processor_id());

		RCU_TRACE(trace_rcu_dyntick(TPS("Entry error: not idle task"),
					    rcu_dynticks_nesting, newval));
		ftrace_dump(DUMP_ALL);
		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
			  current->pid, current->comm,
			  idle->pid, idle->comm); /* must be idle task! */
	}
	rcu_sched_qs(); /* implies rcu_bh_inc() */
	barrier();
	rcu_dynticks_nesting = newval;
}

void linsched_yield(void)
{
	/* If the current task is not the idle task, yield. */
	if (current != idle_task(smp_processor_id()))
		yield();
}

//----------------------------------------------------------------------------------------------------//
//  @func - xilkernel_start
//! @desc
//!   Start the kernel by enabling interrupts and starting to execute the idle task.
//! @return
//!   - Nothing.
//! @note
//!   - Routine does not return.
//! @desc
//----------------------------------------------------------------------------------------------------//
void xilkernel_start (void)
{
    DBG_PRINT("XMK: Process scheduling starts.\r\n");
    Xil_ExceptionEnable();
    idle_task ();                                                       // Does not return
}