linux内核休眠、唤醒流程分析之挂起：Call Notifiers、Freeze任务（三）

不止冬雷和夏雪

于 2020-12-10 15:57:40 发布

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分类专栏：驱动 Android Linux 文章标签： linux android

本文链接：https://blog.youkuaiyun.com/wang_518/article/details/110955002

本文深入探讨Linux内核的休眠挂起过程，详细解析了pm_suspend入口函数及其调用的enter_state函数。在挂起过程中，通过特定机制实现了流程图中的步骤1和步骤2，即调用call notifiers执行过程1，然后通过freeze任务完成对APP和内核线程的冻结，确保系统的稳定挂起。

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在这里插入图片描述

入口函数为pm_suspend

// kernel\power\suspend.c

/**
 * pm_suspend - Externally visible function for suspending the system.
 * @state: System sleep state to enter.
 *
 * Check if the value of @state represents one of the supported states,
 * execute enter_state() and update system suspend statistics.
 */
int pm_suspend(suspend_state_t state)
{
   
   
	int error;

	if (state <= PM_SUSPEND_ON || state >= PM_SUSPEND_MAX)
		return -EINVAL;

	pr_info("suspend entry (%s)\n", mem_sleep_labels[state]);
	error = enter_state(state);
	if (error) {
   
   
		suspend_stats.fail++;
		dpm_save_failed_errno(error);
	} else {
   
   
		suspend_stats.success++;
	}
	pr_info("suspend exit\n");
	return error;
}
EXPORT_SYMBOL(pm_suspend);

这里会执行enter_state函数。

/**
 * enter_state - Do common work needed to enter system sleep state.
 * @state: System sleep state to enter.
 *
 * Make sure that no one else is trying to put the system into a sleep state.
 * Fail if that's not the case.  Otherwise, prepare for system suspend, make the
 * system enter the given sleep state