Re: [RFC] PM: Add PM_RESUME_PREPARE and PM_POST_RESUME notifiers

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Thursday, 1 November 2007 15:40, Alan Stern wrote:
> On Wed, 31 Oct 2007, Rafael J. Wysocki wrote:
> 
> > > (Strictly speaking, we should have two different notification codes for 
> > > PM_POST_HIBERNATION: one for use after the atomic snapshot has been 
> > > created and one for use after it has been restored.  But I'm not going 
> > > to worry about that right now.)
> > 
> > IIRC, the notifiers are not called after creating the image.  Do you think that
> > they should be called at that time?  If so, then why?
> 
> My mistake.  It's easy to forget that even though devices get resumed 
> for writing after the image is created, tasks don't get thawed.  And 
> since tasks don't get thawed, the notifiers shouldn't be called.
> 
> > As far as the patch is concerned, I'd prefer not to add new ioctls(), mainly
> > because there's userland out there that doesn't know about them and we can't
> > make people switch overnight.  I'd prever to move the notifier calls to
> > snapshot_open() and snapshot_release().
> 
> Okay, here's a patch to do things that way.

Thanks.  [I was going to write that myself, but you were faster. :-)]

The patch looks good.

Please sign it off and provide a changelog and I'll forward it to Len.

Greetings,
Rafael


> Index: usb-2.6/Documentation/power/notifiers.txt
> ===================================================================
> --- usb-2.6.orig/Documentation/power/notifiers.txt
> +++ usb-2.6/Documentation/power/notifiers.txt
> @@ -28,6 +28,14 @@ PM_POST_HIBERNATION	The system memory st
>  			hibernation.  Device drivers' .resume() callbacks have
>  			been executed and tasks have been thawed.
>  
> +PM_RESTORE_PREPARE	The system is going to restore a hibernation image.
> +			If all goes well the restored kernel will issue a
> +			PM_POST_HIBERNATION notification.
> +
> +PM_POST_RESTORE		An error occurred during the hibernation restore.
> +			Device drivers' .resume() callbacks have been executed
> +			and tasks have been thawed.
> +
>  PM_SUSPEND_PREPARE	The system is preparing for a suspend.
>  
>  PM_POST_SUSPEND		The system has just resumed or an error occured during
> Index: usb-2.6/include/linux/notifier.h
> ===================================================================
> --- usb-2.6.orig/include/linux/notifier.h
> +++ usb-2.6/include/linux/notifier.h
> @@ -230,6 +230,8 @@ static inline int notifier_to_errno(int 
>  #define PM_POST_HIBERNATION	0x0002 /* Hibernation finished */
>  #define PM_SUSPEND_PREPARE	0x0003 /* Going to suspend the system */
>  #define PM_POST_SUSPEND		0x0004 /* Suspend finished */
> +#define PM_RESTORE_PREPARE	0x0005 /* Going to restore a saved image */
> +#define PM_POST_RESTORE		0x0006 /* Restore failed */
>  
>  /* Console keyboard events.
>   * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
> Index: usb-2.6/kernel/power/disk.c
> ===================================================================
> --- usb-2.6.orig/kernel/power/disk.c
> +++ usb-2.6/kernel/power/disk.c
> @@ -489,6 +489,10 @@ static int software_resume(void)
>  		goto Unlock;
>  	}
>  
> +	error = pm_notifier_call_chain(PM_RESTORE_PREPARE);
> +	if (error)
> +		goto Exit;
> +
>  	error = create_basic_memory_bitmaps();
>  	if (error)
>  		goto Finish;
> @@ -512,6 +516,8 @@ static int software_resume(void)
>   Done:
>  	free_basic_memory_bitmaps();
>   Finish:
> +	pm_notifier_call_chain(PM_POST_RESTORE);
> + Exit:
>  	atomic_inc(&snapshot_device_available);
>  	/* For success case, the suspend path will release the lock */
>   Unlock:
> Index: usb-2.6/kernel/power/user.c
> ===================================================================
> --- usb-2.6.orig/kernel/power/user.c
> +++ usb-2.6/kernel/power/user.c
> @@ -44,6 +44,7 @@ atomic_t snapshot_device_available = ATO
>  static int snapshot_open(struct inode *inode, struct file *filp)
>  {
>  	struct snapshot_data *data;
> +	int error;
>  
>  	if (!atomic_add_unless(&snapshot_device_available, -1, 0))
>  		return -EBUSY;
> @@ -64,9 +65,15 @@ static int snapshot_open(struct inode *i
>  		data->swap = swsusp_resume_device ?
>  			swap_type_of(swsusp_resume_device, 0, NULL) : -1;
>  		data->mode = O_RDONLY;
> +		error = pm_notifier_call_chain(PM_RESTORE_PREPARE);
>  	} else {
>  		data->swap = -1;
>  		data->mode = O_WRONLY;
> +		error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
> +	}
> +	if (error) {
> +		atomic_inc(&snapshot_device_available);
> +		return error;
>  	}
>  	data->frozen = 0;
>  	data->ready = 0;
> @@ -88,6 +95,8 @@ static int snapshot_release(struct inode
>  		thaw_processes();
>  		mutex_unlock(&pm_mutex);
>  	}
> +	pm_notifier_call_chain(data->mode == O_WRONLY ?
> +			PM_POST_HIBERNATION : PM_POST_RESTORE);
>  	atomic_inc(&snapshot_device_available);
>  	return 0;
>  }
> @@ -151,18 +160,13 @@ static int snapshot_ioctl(struct inode *
>  		if (data->frozen)
>  			break;
>  		mutex_lock(&pm_mutex);
> -		error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
> -		if (!error) {
> -			printk("Syncing filesystems ... ");
> -			sys_sync();
> -			printk("done.\n");
> -
> -			error = freeze_processes();
> -			if (error)
> -				thaw_processes();
> -		}
> +		printk("Syncing filesystems ... ");
> +		sys_sync();
> +		printk("done.\n");
> +
> +		error = freeze_processes();
>  		if (error)
> -			pm_notifier_call_chain(PM_POST_HIBERNATION);
> +			thaw_processes();
>  		mutex_unlock(&pm_mutex);
>  		if (!error)
>  			data->frozen = 1;
> @@ -173,7 +177,6 @@ static int snapshot_ioctl(struct inode *
>  			break;
>  		mutex_lock(&pm_mutex);
>  		thaw_processes();
> -		pm_notifier_call_chain(PM_POST_HIBERNATION);
>  		mutex_unlock(&pm_mutex);
>  		data->frozen = 0;
>  		break;