谈谈kernel待机及唤醒

目录

1. 内核待机和唤醒代码分布
2. 待机及唤醒流程分析
3. 如何统计模块唤醒时长

内核待机和唤醒代码分布

1. kernel/power
2. drivers/base/power

待机及唤醒流程分析

可以查看我的csdn博客Linux Kernel and Android 休眠与唤醒(中文版)

如何统计模块唤醒时长

废话不多说，直接贴代码：

drivers/base/power/main.c

static int dpm_run_callback(pm_callback_t cb, struct device *dev,
			    pm_message_t state, char *info)
{
	ktime_t calltime;
	int error;

	if (!cb)
		return 0;

	calltime = initcall_debug_start(dev);

	pm_dev_dbg(dev, state, info);
	trace_device_pm_callback_start(dev, info, state.event);
	error = cb(dev);
	trace_device_pm_callback_end(dev, error);
	suspend_report_result(cb, error);

	initcall_debug_report(dev, calltime, error, state, info);

	return error;
}

具体看下initcall_debug_start及initcall_debug_report两个函数的定义：

static ktime_t initcall_debug_start(struct device *dev)
{
	ktime_t calltime = ktime_set(0, 0);

	if (pm_print_times_enabled) {
		pr_info("calling  %s+ @ %i, parent: %s\n",
			dev_name(dev), task_pid_nr(current),
			dev->parent ? dev_name(dev->parent) : "none");
		calltime = ktime_get();
	}

	return calltime;
}

static void initcall_debug_report(struct device *dev, ktime_t calltime,
				  int error, pm_message_t state, char *info)
{
	ktime_t rettime;
	s64 nsecs;

	rettime = ktime_get();
	nsecs = (s64) ktime_to_ns(ktime_sub(rettime, calltime));

	if (pm_print_times_enabled) {
		pr_info("call %s+ returned %d after %Ld usecs\n", dev_name(dev),
			error, (unsigned long long)nsecs >> 10);
	}
}