/**
 * suspend_prepare - Prepare for entering system sleep state.
 *
 * Common code run for every system sleep state that can be entered (except for
 * hibernation).  Run suspend notifiers, allocate the "suspend" console and
 * freeze processes.
 */
static int suspend_prepare(void)
{
	int error;

	if (!suspend_ops || !suspend_ops->enter)
		return -EPERM;

	pm_prepare_console();

	error = pm_notifier_call_chain(PM_SUSPEND_PREPARE);
	if (error)
		goto Finish;

	error = suspend_freeze_processes();
	if (!error)
		return 0;

	suspend_stats.failed_freeze++;
	dpm_save_failed_step(SUSPEND_FREEZE);
 Finish:
	pm_notifier_call_chain(PM_POST_SUSPEND);
	pm_restore_console();
	return error;
}

/**
 * suspend_prepare - Prepare for entering system sleep state.
 *
 * Common code run for every system sleep state that can be entered (except for
 * hibernation).  Run suspend notifiers, allocate the "suspend" console and
 * freeze processes.
 */
static int suspend_prepare(suspend_state_t state)
{
	int error;

	if (need_suspend_ops(state) && (!suspend_ops || !suspend_ops->enter))
		return -EPERM;

	pm_prepare_console();

	error = pm_notifier_call_chain(PM_SUSPEND_PREPARE);
	if (error)
		goto Finish;

	error = suspend_freeze_processes();
	if (!error)
		return 0;
	log_suspend_abort_reason("One or more tasks refusing to freeze");
	suspend_stats.failed_freeze++;
	dpm_save_failed_step(SUSPEND_FREEZE);
 Finish:
	pm_notifier_call_chain(PM_POST_SUSPEND);
	pm_restore_console();
	return error;
}

static int snapshot_release(struct inode *inode, struct file *filp)
{
	struct snapshot_data *data;

	lock_system_sleep();

	swsusp_free();
	free_basic_memory_bitmaps();
	data = filp->private_data;
	free_all_swap_pages(data->swap);
	if (data->frozen) {
		pm_restore_gfp_mask();
		thaw_processes();
	}
	pm_notifier_call_chain(data->mode == O_RDONLY ?
			PM_POST_HIBERNATION : PM_POST_RESTORE);
	atomic_inc(&snapshot_device_available);

	unlock_system_sleep();

	return 0;
}

static int software_resume(void)
{
	int error;
	unsigned int flags;

	/*
	 * If the user said "noresume".. bail out early.
	 */
	if (noresume)
		return 0;

	/*
	 * name_to_dev_t() below takes a sysfs buffer mutex when sysfs
	 * is configured into the kernel. Since the regular hibernate
	 * trigger path is via sysfs which takes a buffer mutex before
	 * calling hibernate functions (which take pm_mutex) this can
	 * cause lockdep to complain about a possible ABBA deadlock
	 * which cannot happen since we're in the boot code here and
	 * sysfs can't be invoked yet. Therefore, we use a subclass
	 * here to avoid lockdep complaining.
	 */
	mutex_lock_nested(&pm_mutex, SINGLE_DEPTH_NESTING);

	if (swsusp_resume_device)
		goto Check_image;

	if (!strlen(resume_file)) {
		error = -ENOENT;
		goto Unlock;
	}

	pr_debug("PM: Checking image partition %s\n", resume_file);

	/* Check if the device is there */
	swsusp_resume_device = name_to_dev_t(resume_file);
	if (!swsusp_resume_device) {
		/*
		 * Some device discovery might still be in progress; we need
		 * to wait for this to finish.
		 */
		wait_for_device_probe();
		/*
		 * We can't depend on SCSI devices being available after loading
		 * one of their modules until scsi_complete_async_scans() is
		 * called and the resume device usually is a SCSI one.
		 */
		scsi_complete_async_scans();

		swsusp_resume_device = name_to_dev_t(resume_file);
		if (!swsusp_resume_device) {
			error = -ENODEV;
			goto Unlock;
		}
	}

 Check_image:
	pr_debug("PM: Resume from partition %d:%d\n",
		MAJOR(swsusp_resume_device), MINOR(swsusp_resume_device));

	pr_debug("PM: Checking hibernation image.\n");
	error = swsusp_check();
	if (error)
		goto Unlock;

	/* The snapshot device should not be opened while we're running */
	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
		error = -EBUSY;
		swsusp_close(FMODE_READ);
		goto Unlock;
	}

	pm_prepare_console();
	error = pm_notifier_call_chain(PM_RESTORE_PREPARE);
	if (error)
		goto close_finish;

	error = usermodehelper_disable();
	if (error)
		goto close_finish;

	error = create_basic_memory_bitmaps();
	if (error)
		goto close_finish;

	pr_debug("PM: Preparing processes for restore.\n");
	error = prepare_processes();
	if (error) {
		swsusp_close(FMODE_READ);
		goto Done;
	}

	pr_debug("PM: Reading hibernation image.\n");

	error = swsusp_read(&flags);
	swsusp_close(FMODE_READ);
	if (!error)
		hibernation_restore(flags & SF_PLATFORM_MODE);

	printk(KERN_ERR "PM: Restore failed, recovering.\n");
	swsusp_free();
//.........这里部分代码省略.........

int hibernate(void)
{
	int error;

	mutex_lock(&pm_mutex);
	/* The snapshot device should not be opened while we're running */
	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
		error = -EBUSY;
		goto Unlock;
	}

	pm_prepare_console();
	error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
	if (error)
		goto Exit;

	error = usermodehelper_disable();
	if (error)
		goto Exit;

	/* Allocate memory management structures */
	error = create_basic_memory_bitmaps();
	if (error)
		goto Exit;

	printk(KERN_INFO "PM: Syncing filesystems ... ");
	sys_sync();
	printk("done.\n");

	error = prepare_processes();
	if (error)
		goto Finish;

	if (hibernation_test(TEST_FREEZER))
		goto Thaw;

	if (hibernation_testmode(HIBERNATION_TESTPROC))
		goto Thaw;

	error = hibernation_snapshot(hibernation_mode == HIBERNATION_PLATFORM);
	if (error)
		goto Thaw;

	if (in_suspend) {
		unsigned int flags = 0;

		if (hibernation_mode == HIBERNATION_PLATFORM)
			flags |= SF_PLATFORM_MODE;
		pr_debug("PM: writing image.\n");
		error = swsusp_write(flags);
		swsusp_free();
		if (!error)
			power_down();
	} else {
		pr_debug("PM: Image restored successfully.\n");
	}

 Thaw:
	thaw_processes();
 Finish:
	free_basic_memory_bitmaps();
	usermodehelper_enable();
 Exit:
	pm_notifier_call_chain(PM_POST_HIBERNATION);
	pm_restore_console();
	atomic_inc(&snapshot_device_available);
 Unlock:
	mutex_unlock(&pm_mutex);
	return error;
}

//.........这里部分代码省略.........
	}

	pr_debug("PM: Checking hibernation image partition %s\n", resume_file);

	if (resume_delay) {
		printk(KERN_INFO "Waiting %dsec before reading resume device...\n",
			resume_delay);
		ssleep(resume_delay);
	}

	/* Check if the device is there */
	swsusp_resume_device = name_to_dev_t(resume_file);

	/*
	 * name_to_dev_t is ineffective to verify parition if resume_file is in
	 * integer format. (e.g. major:minor)
	 */
	if (isdigit(resume_file[0]) && resume_wait) {
		int partno;
		while (!get_gendisk(swsusp_resume_device, &partno))
			msleep(10);
	}

	if (!swsusp_resume_device) {
		/*
		 * Some device discovery might still be in progress; we need
		 * to wait for this to finish.
		 */
		wait_for_device_probe();

		if (resume_wait) {
			while ((swsusp_resume_device = name_to_dev_t(resume_file)) == 0)
				msleep(10);
			async_synchronize_full();
		}

		swsusp_resume_device = name_to_dev_t(resume_file);
		if (!swsusp_resume_device) {
			error = -ENODEV;
			goto Unlock;
		}
	}

 Check_image:
	pr_debug("PM: Hibernation image partition %d:%d present\n",
		MAJOR(swsusp_resume_device), MINOR(swsusp_resume_device));

	pr_debug("PM: Looking for hibernation image.\n");
	error = swsusp_check();
	if (error)
		goto Unlock;

	/* The snapshot device should not be opened while we're running */
	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
		error = -EBUSY;
		swsusp_close(FMODE_READ);
		goto Unlock;
	}

	pm_prepare_console();
	error = pm_notifier_call_chain(PM_RESTORE_PREPARE);
	if (error)
		goto Close_Finish;

	pr_debug("PM: Preparing processes for restore.\n");
	error = freeze_processes();
	if (error)
		goto Close_Finish;

	pr_debug("PM: Loading hibernation image.\n");

	lock_device_hotplug();
	error = create_basic_memory_bitmaps();
	if (error)
		goto Thaw;

	error = swsusp_read(&flags);
	swsusp_close(FMODE_READ);
	if (!error)
		hibernation_restore(flags & SF_PLATFORM_MODE);

	printk(KERN_ERR "PM: Failed to load hibernation image, recovering.\n");
	swsusp_free();
	free_basic_memory_bitmaps();
 Thaw:
	unlock_device_hotplug();
	thaw_processes();
 Finish:
	pm_notifier_call_chain(PM_POST_RESTORE);
	pm_restore_console();
	atomic_inc(&snapshot_device_available);
	/* For success case, the suspend path will release the lock */
 Unlock:
	mutex_unlock(&pm_mutex);
	pr_debug("PM: Hibernation image not present or could not be loaded.\n");
	return error;
 Close_Finish:
	swsusp_close(FMODE_READ);
	goto Finish;
}

/**
 * hibernate - Carry out system hibernation, including saving the image.
 */
int hibernate(void)
{
	int error;

	if (!hibernation_available()) {
		pr_debug("PM: Hibernation not available.\n");
		return -EPERM;
	}

	lock_system_sleep();
	/* The snapshot device should not be opened while we're running */
	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
		error = -EBUSY;
		goto Unlock;
	}

	pm_prepare_console();
	error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
	if (error)
		goto Exit;

	printk(KERN_INFO "PM: Syncing filesystems ... ");
	sys_sync();
	printk("done.\n");

	error = freeze_processes();
	if (error)
		goto Exit;

	lock_device_hotplug();
	/* Allocate memory management structures */
	error = create_basic_memory_bitmaps();
	if (error)
		goto Thaw;

	error = hibernation_snapshot(hibernation_mode == HIBERNATION_PLATFORM);
	if (error || freezer_test_done)
		goto Free_bitmaps;

	if (in_suspend) {
		unsigned int flags = 0;

		if (hibernation_mode == HIBERNATION_PLATFORM)
			flags |= SF_PLATFORM_MODE;
		if (nocompress)
			flags |= SF_NOCOMPRESS_MODE;
		else
		        flags |= SF_CRC32_MODE;

		pr_debug("PM: writing image.\n");
		error = swsusp_write(flags);
		swsusp_free();
		if (!error)
			power_down();
		in_suspend = 0;
		pm_restore_gfp_mask();
	} else {
		pr_debug("PM: Image restored successfully.\n");
	}

 Free_bitmaps:
	free_basic_memory_bitmaps();
 Thaw:
	unlock_device_hotplug();
	thaw_processes();

	/* Don't bother checking whether freezer_test_done is true */
	freezer_test_done = false;
 Exit:
	pm_notifier_call_chain(PM_POST_HIBERNATION);
	pm_restore_console();
	atomic_inc(&snapshot_device_available);
 Unlock:
	unlock_system_sleep();
	return error;
}

static int software_resume(void)
{
	int error;
	unsigned int flags;

	/*
	 * name_to_dev_t() below takes a sysfs buffer mutex when sysfs
	 * is configured into the kernel. Since the regular hibernate
	 * trigger path is via sysfs which takes a buffer mutex before
	 * calling hibernate functions (which take pm_mutex) this can
	 * cause lockdep to complain about a possible ABBA deadlock
	 * which cannot happen since we're in the boot code here and
	 * sysfs can't be invoked yet. Therefore, we use a subclass
	 * here to avoid lockdep complaining.
	 */
	mutex_lock_nested(&pm_mutex, SINGLE_DEPTH_NESTING);
	if (!swsusp_resume_device) {
		if (!strlen(resume_file)) {
			mutex_unlock(&pm_mutex);
			return -ENOENT;
		}
		swsusp_resume_device = name_to_dev_t(resume_file);
		pr_debug("PM: Resume from partition %s\n", resume_file);
	} else {
		pr_debug("PM: Resume from partition %d:%d\n",
				MAJOR(swsusp_resume_device),
				MINOR(swsusp_resume_device));
	}

	if (noresume) {
		/**
		 * FIXME: If noresume is specified, we need to find the
		 * partition and reset it back to normal swap space.
		 */
		mutex_unlock(&pm_mutex);
		return 0;
	}

	pr_debug("PM: Checking hibernation image.\n");
	error = swsusp_check();
	if (error)
		goto Unlock;

	/* The snapshot device should not be opened while we're running */
	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
		error = -EBUSY;
		goto Unlock;
	}

	pm_prepare_console();
	error = pm_notifier_call_chain(PM_RESTORE_PREPARE);
	if (error)
		goto Finish;

	error = create_basic_memory_bitmaps();
	if (error)
		goto Finish;

	pr_debug("PM: Preparing processes for restore.\n");
	error = prepare_processes();
	if (error) {
		swsusp_close();
		goto Done;
	}

	pr_debug("PM: Reading hibernation image.\n");

	error = swsusp_read(&flags);
	if (!error)
		hibernation_restore(flags & SF_PLATFORM_MODE);

	printk(KERN_ERR "PM: Restore failed, recovering.\n");
	swsusp_free();
	thaw_processes();
 Done:
	free_basic_memory_bitmaps();
 Finish:
	pm_notifier_call_chain(PM_POST_RESTORE);
	pm_restore_console();
	atomic_inc(&snapshot_device_available);
	/* For success case, the suspend path will release the lock */
 Unlock:
	mutex_unlock(&pm_mutex);
	pr_debug("PM: Resume from disk failed.\n");
	return error;
}

static void __toi_power_down(int method)
{
	int error;

	toi_cond_pause(1, test_action_state(TOI_REBOOT) ? "Ready to reboot." :
			"Powering down.");

	if (test_result_state(TOI_ABORTED))
		goto out;

	if (test_action_state(TOI_REBOOT))
		kernel_restart(NULL);

	switch (method) {
	case 0:
		break;
	case 3:
		/*
		 * Re-read the overwritten part of pageset2 to make post-resume
		 * faster.
		 */
		if (read_pageset2(1))
			panic("Attempt to reload pagedir 2 failed. "
					"Try rebooting.");

		pm_prepare_console();

		error = pm_notifier_call_chain(PM_SUSPEND_PREPARE);
		if (!error) {
			pm_restore_gfp_mask();
			error = suspend_devices_and_enter(PM_SUSPEND_MEM);
			pm_restrict_gfp_mask();
			if (!error)
				did_suspend_to_both = 1;
		}
		pm_notifier_call_chain(PM_POST_SUSPEND);
		pm_restore_console();

        // jonathan.jmchen: FIXME, Create API to add another wakeup source to power down,
        // if system is idle after xxx (e.g., 5 min) without user interaction!!

		/* Success - we're now post-resume-from-ram */
		if (did_suspend_to_both)
			return;

		/* Failed to suspend to ram - do normal power off */
		break;
	case 4:
		/*
		 * If succeeds, doesn't return. If fails, do a simple
		 * powerdown.
		 */
		hibernation_platform_enter();
		break;
	case 5:
		/* Historic entry only now */
		break;
	}

	if (method && method != 5)
		toi_cond_pause(1,
			"Falling back to alternate power off method.");

	if (test_result_state(TOI_ABORTED))
		goto out;

	kernel_power_off();
	kernel_halt();
	toi_cond_pause(1, "Powerdown failed.");
	while (1)
		cpu_relax();

out:
	if (read_pageset2(1))
		panic("Attempt to reload pagedir 2 failed. Try rebooting.");
	return;
}