static int suspend_prepare(suspend_state_t state)
{
	int error;
	unsigned int free_pages;

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

	pm_prepare_console();

	error = disable_nonboot_cpus();
	if (error)
		goto Enable_cpu;

	if (freeze_processes()) {
		error = -EAGAIN;
		goto Thaw;
	}

	if ((free_pages = nr_free_pages()) < FREE_PAGE_NUMBER) {
		pr_debug("PM: free some memory\n");
		shrink_all_memory(FREE_PAGE_NUMBER - free_pages);
		if (nr_free_pages() < FREE_PAGE_NUMBER) {
			error = -ENOMEM;
			printk(KERN_ERR "PM: No enough memory\n");
			goto Thaw;
		}
	}

	if (pm_ops->prepare) {
		if ((error = pm_ops->prepare(state)))
			goto Thaw;
	}

	suspend_console();
	if ((error = device_suspend(PMSG_SUSPEND))) {
		printk(KERN_ERR "Some devices failed to suspend\n");
		goto Finish;
	}
	return 0;
 Finish:
	if (pm_ops->finish)
		pm_ops->finish(state);
 Thaw:
	thaw_processes();
 Enable_cpu:
	enable_nonboot_cpus();
	pm_restore_console();
	return error;
}

int hibernation_restore(int platform_mode)
{
	int error;

	pm_prepare_console();
	suspend_console();
	error = dpm_suspend_start(PMSG_QUIESCE);
	if (!error) {
		error = resume_target_kernel(platform_mode);
		dpm_resume_end(PMSG_RECOVER);
	}
	resume_console();
	pm_restore_console();
	return error;
}

int hibernation_restore(int platform_mode)
{
	int error;
	gfp_t saved_mask;

	pm_prepare_console();
	suspend_console();
	saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
	error = dpm_suspend_start(PMSG_QUIESCE);
	if (!error) {
		error = resume_target_kernel(platform_mode);
		dpm_resume_end(PMSG_RECOVER);
	}
	set_gfp_allowed_mask(saved_mask);
	resume_console();
	pm_restore_console();
	return error;
}

/**
 *	suspend_prepare - Do prep work before entering low-power state.
 *
 *	This is common code that is called for each state that we're entering.
 *	Run suspend notifiers, allocate a console and stop all 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 = usermodehelper_disable();
	if (error)
		goto Finish;

	/* Add a workaround to reset the system (causing a reboot) after
	 * timeout occurs. We met suspect system hang in try_to_freeze_tasks()
	 * without return even in successful case (When this issue occurs, dmesg
	 * looks like "Freezing user space processes ... (elapsed 0.02 seconds)"
	 * without proper "done" in the tail, or "Freezing remaining freezable
	 * tasks ... (elapsed 0.01 seconds) without proper "done" either.
	 *
	 * FIXME: Figure out the root cause of this system hang.
	 */
	freezer_expire_start();
	error = suspend_freeze_processes();
	freezer_expire_finish("freeze processes");
	if (!error)
		return 0;

	suspend_thaw_processes();
	usermodehelper_enable();
 Finish:
	pm_notifier_call_chain(PM_POST_SUSPEND);
	pm_restore_console();
	return error;
}

static void do_software_suspend(void)
{
	if (arch_prepare_suspend()) {
		printk("%sArchitecture failed to prepare\n", name_suspend);
		return;
	}		
	if (pm_prepare_console())
		printk( "%sCan't allocate a console... proceeding\n", name_suspend);
	if (!prepare_suspend_processes()) {

		/* At this point, all user processes and "dangerous"
                   kernel threads are stopped. Free some memory, as we
                   need half of memory free. */

		free_some_memory();
		
		/* No need to invalidate any vfsmnt list -- 
		 * they will be valid after resume, anyway.
		 */
		blk_run_queues();

		/* Save state of all device drivers, and stop them. */		   
		if(drivers_suspend()==0)
			/* If stopping device drivers worked, we proceed basically into
			 * suspend_save_image.
			 *
			 * do_magic(0) returns after system is resumed.
			 *
			 * do_magic() copies all "used" memory to "free" memory, then
			 * unsuspends all device drivers, and writes memory to disk
			 * using normal kernel mechanism.
			 */
			do_magic(0);
		thaw_processes();
	}
	software_suspend_enabled = 1;
	MDELAY(1000);
	pm_restore_console();
}

/**
 *	software_resume - Resume from a saved image.
 *
 *	Called as a late_initcall (so all devices are discovered and 
 *	initialized), we call swsusp to see if we have a saved image or not.
 *	If so, we quiesce devices, then restore the saved image. We will 
 *	return above (in pm_suspend_disk() ) if everything goes well. 
 *	Otherwise, we fail gracefully and return to the normally 
 *	scheduled program.
 *
 */
static int __init software_resume(void)
{
	if (num_online_cpus() > 1) {
		printk(KERN_WARNING "Software Suspend has malfunctioning SMP support. Disabled :(\n");	
		return -EINVAL;
	}
	/* We enable the possibility of machine suspend */
	software_suspend_enabled = 1;
	if (!resume_status)
		return 0;

	printk( "%s", name_resume );
	if (resume_status == NORESUME) {
		if(resume_file[0])
			read_suspend_image(resume_file, 1);
		printk( "disabled\n" );
		return 0;
	}
	MDELAY(1000);

	if (pm_prepare_console())
		printk("swsusp: Can't allocate a console... proceeding\n");

	if (!resume_file[0] && resume_status == RESUME_SPECIFIED) {
		printk( "suspension device unspecified\n" );
		return -EINVAL;
	}

	printk( "resuming from %s\n", resume_file);
	if (read_suspend_image(resume_file, 0))
		goto read_failure;
	do_magic(1);
	panic("This never returns");

read_failure:
	pm_restore_console();
	return 0;
}

/**
 *	suspend_prepare - Do prep work before entering low-power state.
 *
 *	This is common code that is called for each state that we're entering.
 *	Run suspend notifiers, allocate a console and stop all processes.
 */
static int suspend_prepare(void)
{
	int error;

	if (!suspend_ops || !suspend_ops->enter)
		return -EPERM;
/*                                                                   */
#ifndef CONFIG_FB_EARLYSUSPEND
	pm_prepare_console();
#endif
/*                                                                   */

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

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

	error = suspend_freeze_processes();
	if (error) {
		suspend_stats.failed_freeze++;
		dpm_save_failed_step(SUSPEND_FREEZE);
	} else
		return 0;

	suspend_thaw_processes();
	usermodehelper_enable();
 Finish:
	pm_notifier_call_chain(PM_POST_SUSPEND);
/*                                                                   */
#ifndef CONFIG_FB_EARLYSUSPEND	
	pm_restore_console();
#endif
/*                                                                   */	
	return error;
}

/**
 * hibernation_restore - Quiesce devices and restore from a hibernation image.
 * @platform_mode: If set, use platform driver to prepare for the transition.
 *
 * This routine must be called with pm_mutex held.  If it is successful, control
 * reappears in the restored target kernel in hibernation_snapshot().
 */
int hibernation_restore(int platform_mode)
{
	int error;

	pm_prepare_console();
	suspend_console();
	pm_restrict_gfp_mask();
	error = dpm_suspend_start(PMSG_QUIESCE);
	if (!error) {
		error = resume_target_kernel(platform_mode);
		/*
		 * The above should either succeed and jump to the new kernel,
		 * or return with an error. Otherwise things are just
		 * undefined, so let's be paranoid.
		 */
		BUG_ON(!error);
	}
	dpm_resume_end(PMSG_RECOVER);
	pm_restore_gfp_mask();
	resume_console();
	pm_restore_console();
	return error;
}

static int prepare_processes(void)
{
	int error = 0;

	pm_prepare_console();

	error = disable_nonboot_cpus();
	if (error)
		goto enable_cpus;

	if (freeze_processes()) {
		error = -EBUSY;
		goto thaw;
	}

	if (pm_disk_mode == PM_DISK_TESTPROC) {
		printk("swsusp debug: Waiting for 5 seconds.\n");
		mdelay(5000);
		goto thaw;
	}

	error = platform_prepare();
	if (error)
		goto thaw;

	/* Free memory before shutting down devices. */
	if (!(error = swsusp_shrink_memory()))
		return 0;

	platform_finish();
 thaw:
	thaw_processes();
 enable_cpus:
	enable_nonboot_cpus();
	pm_restore_console();
	return error;
}

int hibernation_restore(int platform_mode)
{
	int error;

	pm_prepare_console();
	suspend_console();
	error = device_suspend(PMSG_QUIESCE);
	if (error)
		goto Finish;

	error = platform_pre_restore(platform_mode);
	if (!error) {
		error = disable_nonboot_cpus();
		if (!error)
			error = resume_target_kernel();
		enable_nonboot_cpus();
	}
	platform_restore_cleanup(platform_mode);
	device_resume(PMSG_RECOVER);
 Finish:
	resume_console();
	pm_restore_console();
	return error;
}

int hibernation_restore(int platform_mode)
{
	int error;

	pm_prepare_console();
	suspend_console();
	error = device_suspend(PMSG_PRETHAW);
	if (error)
		goto Finish;

	error = platform_pre_restore(platform_mode);
	if (!error) {
		error = disable_nonboot_cpus();
		if (!error)
			error = swsusp_resume();
		enable_nonboot_cpus();
	}
	platform_restore_cleanup(platform_mode);
	device_resume();
 Finish:
	resume_console();
	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 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;
}

//.........这里部分代码省略.........
	 * 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("Checking hibernation image partition %s\n", resume_file);

	if (resume_delay) {
		pr_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("Hibernation image partition %d:%d present\n",
		MAJOR(swsusp_resume_device), MINOR(swsusp_resume_device));

	pr_debug("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, -1, &nr_calls);
	if (error) {
		nr_calls--;
		goto Close_Finish;
	}

	pr_debug("Preparing processes for restore.\n");
	error = freeze_processes();
	if (error)
		goto Close_Finish;
	error = load_image_and_restore();
	thaw_processes();
 Finish:
	__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
	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("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, nr_calls = 0;
	bool snapshot_test = false;

	if (!hibernation_available()) {
		pr_debug("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, -1, &nr_calls);
	if (error) {
		nr_calls--;
		goto Exit;
	}

	pr_info("Syncing filesystems ... \n");
	sys_sync();
	pr_info("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("Writing image.\n");
		error = swsusp_write(flags);
		swsusp_free();
		if (!error) {
			if (hibernation_mode == HIBERNATION_TEST_RESUME)
				snapshot_test = true;
			else
				power_down();
		}
		in_suspend = 0;
		pm_restore_gfp_mask();
	} else {
		pr_debug("Image restored successfully.\n");
	}

 Free_bitmaps:
	free_basic_memory_bitmaps();
 Thaw:
	unlock_device_hotplug();
	if (snapshot_test) {
		pr_debug("Checking hibernation image\n");
		error = swsusp_check();
		if (!error)
			error = load_image_and_restore();
	}
	thaw_processes();

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

//.........这里部分代码省略.........
		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();
		}

		/*
		 * 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: 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;

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

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

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

	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();
	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: Hibernation image not present or could not be loaded.\n");
	return error;
close_finish:
	swsusp_close(FMODE_READ);
	goto Finish;
}

static int snapshot_ioctl(struct inode *inode, struct file *filp,
                          unsigned int cmd, unsigned long arg)
{
    int error = 0;
    struct snapshot_data *data;
    loff_t offset, avail;

    if (_IOC_TYPE(cmd) != SNAPSHOT_IOC_MAGIC)
        return -ENOTTY;
    if (_IOC_NR(cmd) > SNAPSHOT_IOC_MAXNR)
        return -ENOTTY;
    if (!capable(CAP_SYS_ADMIN))
        return -EPERM;

    data = filp->private_data;

    switch (cmd) {

    case SNAPSHOT_FREEZE:
        if (data->frozen)
            break;
        down(&pm_sem);
        disable_nonboot_cpus();
        if (freeze_processes()) {
            thaw_processes();
            enable_nonboot_cpus();
            error = -EBUSY;
        }
        up(&pm_sem);
        if (!error)
            data->frozen = 1;
        break;

    case SNAPSHOT_UNFREEZE:
        if (!data->frozen)
            break;
        down(&pm_sem);
        thaw_processes();
        enable_nonboot_cpus();
        up(&pm_sem);
        data->frozen = 0;
        break;

    case SNAPSHOT_ATOMIC_SNAPSHOT:
        if (data->mode != O_RDONLY || !data->frozen  || data->ready) {
            error = -EPERM;
            break;
        }
        down(&pm_sem);
        /* Free memory before shutting down devices. */
        error = swsusp_shrink_memory();
        if (!error) {
            error = device_suspend(PMSG_FREEZE);
            if (!error) {
                in_suspend = 1;
                error = swsusp_suspend();
                device_resume();
            }
        }
        up(&pm_sem);
        if (!error)
            error = put_user(in_suspend, (unsigned int __user *)arg);
        if (!error)
            data->ready = 1;
        break;

    case SNAPSHOT_ATOMIC_RESTORE:
        if (data->mode != O_WRONLY || !data->frozen ||
                !snapshot_image_loaded(&data->handle)) {
            error = -EPERM;
            break;
        }
        down(&pm_sem);
        pm_prepare_console();
        error = device_suspend(PMSG_FREEZE);
        if (!error) {
            error = swsusp_resume();
            device_resume();
        }
        pm_restore_console();
        up(&pm_sem);
        break;

    case SNAPSHOT_FREE:
        swsusp_free();
        memset(&data->handle, 0, sizeof(struct snapshot_handle));
        data->ready = 0;
        break;

    case SNAPSHOT_SET_IMAGE_SIZE:
        image_size = arg;
        break;

    case SNAPSHOT_AVAIL_SWAP:
        avail = count_swap_pages(data->swap, 1);
        avail <<= PAGE_SHIFT;
        error = put_user(avail, (loff_t __user *)arg);
        break;

    case SNAPSHOT_GET_SWAP_PAGE:
//.........这里部分代码省略.........

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;
}

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;
}