diff mbox

[16/16] Thermal: use plist instead of list

Message ID 1342679480-5336-17-git-send-email-rui.zhang@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Zhang, Rui July 19, 2012, 6:31 a.m. UTC
so that the thermal manager can easily find out
the deepest cooling state request for a cooling device.

cdev->lock is also introduced in this patch to protect this plist.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
---
 drivers/thermal/thermal_sys.c |   84 ++++++++++++++++++++++++++---------------
 include/linux/thermal.h       |    4 +-
 2 files changed, 57 insertions(+), 31 deletions(-)

Comments

Rafael Wysocki July 19, 2012, 9:45 p.m. UTC | #1
On Thursday, July 19, 2012, Zhang Rui wrote:
> so that the thermal manager can easily find out
> the deepest cooling state request for a cooling device.
> 
> cdev->lock is also introduced in this patch to protect this plist.
> 
> Signed-off-by: Zhang Rui <rui.zhang@intel.com>

I'm not sure if this is actually better than without the plist.

The plist manipulations in thermal_zone_trip_update() look like they
can add quite some overhead in some situations.

Do you have any quantitative justification for this change?

Rafael


> ---
>  drivers/thermal/thermal_sys.c |   84 ++++++++++++++++++++++++++---------------
>  include/linux/thermal.h       |    4 +-
>  2 files changed, 57 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
> index a40dda1..9f56250 100644
> --- a/drivers/thermal/thermal_sys.c
> +++ b/drivers/thermal/thermal_sys.c
> @@ -54,11 +54,10 @@ struct thermal_instance {
>  	int trip;
>  	unsigned long upper;	/* Highest cooling state for this trip point */
>  	unsigned long lower;	/* Lowest cooling state for this trip point */
> -	unsigned long target;	/* expected cooling state */
>  	char attr_name[THERMAL_NAME_LENGTH];
>  	struct device_attribute attr;
>  	struct list_head tz_node; /* node in tz->instances */
> -	struct list_head cdev_node; /* node in cdev->instances */
> +	struct plist_node cdev_node; /* node in cdev->instances */
>  };
>  
>  static DEFINE_IDR(thermal_tz_idr);
> @@ -787,7 +786,7 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
>  	dev->trip = trip;
>  	dev->upper = upper;
>  	dev->lower = lower;
> -	dev->target = -1;
> +	plist_node_init(&dev->cdev_node, -1);
>  
>  	result = get_idr(&tz->idr, &tz->lock, &dev->id);
>  	if (result)
> @@ -809,6 +808,7 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
>  		goto remove_symbol_link;
>  
>  	mutex_lock(&tz->lock);
> +	mutex_lock(&cdev->lock);
>  	list_for_each_entry(pos, &tz->instances, tz_node)
>  	    if (pos->tz == tz && pos->trip == trip && pos->cdev == cdev) {
>  		result = -EEXIST;
> @@ -816,8 +816,9 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
>  	}
>  	if (!result) {
>  		list_add_tail(&dev->tz_node, &tz->instances);
> -		list_add_tail(&dev->cdev_node, &cdev->instances);
> +		plist_add(&dev->cdev_node, &cdev->instances);
>  	}
> +	mutex_unlock(&cdev->lock);
>  	mutex_unlock(&tz->lock);
>  
>  	if (!result)
> @@ -850,14 +851,17 @@ int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
>  	struct thermal_instance *pos, *next;
>  
>  	mutex_lock(&tz->lock);
> +	mutex_lock(&cdev->lock);
>  	list_for_each_entry_safe(pos, next, &tz->instances, tz_node) {
>  		if (pos->tz == tz && pos->trip == trip && pos->cdev == cdev) {
>  			list_del(&pos->tz_node);
> -			list_del(&pos->cdev_node);
> +			plist_del(&pos->cdev_node, &pos->cdev->instances);
> +			mutex_unlock(&cdev->lock);
>  			mutex_unlock(&tz->lock);
>  			goto unbind;
>  		}
>  	}
> +	mutex_unlock(&cdev->lock);
>  	mutex_unlock(&tz->lock);
>  
>  	return -ENODEV;
> @@ -923,7 +927,8 @@ thermal_cooling_device_register(char *type, void *devdata,
>  	}
>  
>  	strcpy(cdev->type, type);
> -	INIT_LIST_HEAD(&cdev->instances);
> +	plist_head_init(&cdev->instances);
> +	mutex_init(&cdev->lock);
>  	cdev->ops = ops;
>  	cdev->updated = 1;
>  	cdev->device.class = &thermal_class;
> @@ -1019,26 +1024,21 @@ EXPORT_SYMBOL(thermal_cooling_device_unregister);
>  
>  static void thermal_zone_do_update(struct thermal_zone_device *tz)
>  {
> -	struct thermal_instance *instance1, *instance2;
> +	struct thermal_instance *instance;
> +	struct plist_node *node;
>  	struct thermal_cooling_device *cdev;
> -	int target;
>  
> -	list_for_each_entry(instance1, &tz->instances, tz_node) {
> -		cdev = instance1->cdev;
> +	list_for_each_entry(instance, &tz->instances, tz_node) {
> +		cdev = instance->cdev;
>  
>  		/* cooling device has already been updated*/
>  		if (cdev->updated)
>  			continue;
>  
> -		target = 0;
> -		/* Make sure cdev enters the deepest cooling state */
> -		list_for_each_entry(instance2, &cdev->instances, cdev_node) {
> -			if (instance2->target == -1)
> -				continue;
> -			if (instance2->target > target)
> -				target = instance2->target;
> -		}
> -		cdev->ops->set_cur_state(cdev, target);
> +		/* Deepest cooling state required */
> +		node = plist_last(&cdev->instances);
> +
> +		cdev->ops->set_cur_state(cdev, node->prio < 0 ? 0 : node->prio);
>  		cdev->updated = 1;
>  	}
>  }
> @@ -1064,7 +1064,7 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
>  {
>  	struct thermal_instance *instance;
>  	struct thermal_cooling_device *cdev = NULL;
> -	unsigned long cur_state, max_state;
> +	unsigned long cur_state, max_state, target_state;
>  	long trip_temp;
>  	enum thermal_trip_type trip_type;
>  	enum thermal_trend trend;
> @@ -1088,21 +1088,29 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
>  
>  			cdev->ops->get_cur_state(cdev, &cur_state);
>  			cdev->ops->get_max_state(cdev, &max_state);
> -
> +			target_state = cur_state;
>  			if (trend == THERMAL_TREND_RAISING) {
> -				cur_state = cur_state < instance->upper ?
> +				target_state = cur_state < instance->upper ?
>  					    (cur_state + 1) : instance->upper;
>  			} else if (trend == THERMAL_TREND_DROPPING) {
> -				cur_state = cur_state > instance->lower ?
> +				target_state = cur_state > instance->lower ?
>  				    (cur_state - 1) : instance->lower;
>  			}
>  
> +			if (target_state == cur_state)
> +				continue;
> +
>  			/* activate a passive thermal instance */
>  			if (trip_type == THERMAL_TRIP_PASSIVE &&
> -			    instance->target == -1)
> +			    instance->cdev_node.prio == -1)
>  				tz->passive++;
>  
> -			instance->target = cur_state;
> +			mutex_lock(&cdev->lock);
> +			plist_del(&instance->cdev_node, &cdev->instances);
> +			plist_node_init(&instance->cdev_node, target_state);
> +			plist_add(&instance->cdev_node, &cdev->instances);
> +			mutex_unlock(&cdev->lock);
> +
>  			cdev->updated = 0; /* cooling device needs update */
>  		}
>  	} else {	/* below trip */
> @@ -1111,20 +1119,36 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
>  				continue;
>  
>  			/* Do not use the deacitve thermal instance */
> -			if (instance->target == -1)
> +			if (instance->cdev_node.prio == -1)
>  				continue;
>  			cdev = instance->cdev;
>  			cdev->ops->get_cur_state(cdev, &cur_state);
>  
> -			cur_state = cur_state > instance->lower ?
> +			target_state = cur_state > instance->lower ?
>  				    (cur_state - 1) : -1;
>  
> +			if (target_state == cur_state)
> +				continue;
> +
>  			/* deactivate a passive thermal instance */
>  			if (trip_type == THERMAL_TRIP_PASSIVE &&
> -			    cur_state == -1)
> +			    target_state == -1)
>  				tz->passive--;
> -			instance->target = cur_state;
> -			cdev->updated = 0; /* cooling device needs update */
> +
> +			mutex_lock(&cdev->lock);
> +			plist_del(&instance->cdev_node, &cdev->instances);
> +			plist_node_init(&instance->cdev_node, target_state);
> +			plist_add(&instance->cdev_node, &cdev->instances);
> +			mutex_unlock(&cdev->lock);
> +
> +			/*
> +			 * cooling device needs update.
> +			 * But if the target_state is -1, it means that
> +			 * the cooling device is already in cooling state 0,
> +			 * thus we do not need update
> +			 */
> +			if (target_state != -1)
> +				cdev->updated = 0;
>  		}
>  	}
>  
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index f725eb9..376a59e 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -28,6 +28,7 @@
>  #include <linux/idr.h>
>  #include <linux/device.h>
>  #include <linux/workqueue.h>
> +#include <linux/plist.h>
>  
>  struct thermal_zone_device;
>  struct thermal_cooling_device;
> @@ -93,7 +94,8 @@ struct thermal_cooling_device {
>  	void *devdata;
>  	const struct thermal_cooling_device_ops *ops;
>  	int updated; /* 1 if the cooling device does not need update */
> -	struct list_head instances;
> +	struct mutex lock;
> +	struct plist_head instances;
>  	struct list_head node;
>  };
>  
> 

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Zhang, Rui July 24, 2012, 2:13 a.m. UTC | #2
On ?, 2012-07-19 at 23:45 +0200, Rafael J. Wysocki wrote:
> On Thursday, July 19, 2012, Zhang Rui wrote:
> > so that the thermal manager can easily find out
> > the deepest cooling state request for a cooling device.
> > 
> > cdev->lock is also introduced in this patch to protect this plist.
> > 
> > Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> 
> I'm not sure if this is actually better than without the plist.
> 
> The plist manipulations in thermal_zone_trip_update() look like they
> can add quite some overhead in some situations.
> 
> Do you have any quantitative justification for this change?
> 
No.
I made this change based on Eduardo's suggestion.
currently, as there are not too many nodes in the list, I don't think we
can get any measurable benefit for now.

Eduardo, I guess you must have more to say on this. :p

thanks,
rui

> Rafael
> 
> 
> > ---
> >  drivers/thermal/thermal_sys.c |   84 ++++++++++++++++++++++++++---------------
> >  include/linux/thermal.h       |    4 +-
> >  2 files changed, 57 insertions(+), 31 deletions(-)
> > 
> > diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
> > index a40dda1..9f56250 100644
> > --- a/drivers/thermal/thermal_sys.c
> > +++ b/drivers/thermal/thermal_sys.c
> > @@ -54,11 +54,10 @@ struct thermal_instance {
> >  	int trip;
> >  	unsigned long upper;	/* Highest cooling state for this trip point */
> >  	unsigned long lower;	/* Lowest cooling state for this trip point */
> > -	unsigned long target;	/* expected cooling state */
> >  	char attr_name[THERMAL_NAME_LENGTH];
> >  	struct device_attribute attr;
> >  	struct list_head tz_node; /* node in tz->instances */
> > -	struct list_head cdev_node; /* node in cdev->instances */
> > +	struct plist_node cdev_node; /* node in cdev->instances */
> >  };
> >  
> >  static DEFINE_IDR(thermal_tz_idr);
> > @@ -787,7 +786,7 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
> >  	dev->trip = trip;
> >  	dev->upper = upper;
> >  	dev->lower = lower;
> > -	dev->target = -1;
> > +	plist_node_init(&dev->cdev_node, -1);
> >  
> >  	result = get_idr(&tz->idr, &tz->lock, &dev->id);
> >  	if (result)
> > @@ -809,6 +808,7 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
> >  		goto remove_symbol_link;
> >  
> >  	mutex_lock(&tz->lock);
> > +	mutex_lock(&cdev->lock);
> >  	list_for_each_entry(pos, &tz->instances, tz_node)
> >  	    if (pos->tz == tz && pos->trip == trip && pos->cdev == cdev) {
> >  		result = -EEXIST;
> > @@ -816,8 +816,9 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
> >  	}
> >  	if (!result) {
> >  		list_add_tail(&dev->tz_node, &tz->instances);
> > -		list_add_tail(&dev->cdev_node, &cdev->instances);
> > +		plist_add(&dev->cdev_node, &cdev->instances);
> >  	}
> > +	mutex_unlock(&cdev->lock);
> >  	mutex_unlock(&tz->lock);
> >  
> >  	if (!result)
> > @@ -850,14 +851,17 @@ int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
> >  	struct thermal_instance *pos, *next;
> >  
> >  	mutex_lock(&tz->lock);
> > +	mutex_lock(&cdev->lock);
> >  	list_for_each_entry_safe(pos, next, &tz->instances, tz_node) {
> >  		if (pos->tz == tz && pos->trip == trip && pos->cdev == cdev) {
> >  			list_del(&pos->tz_node);
> > -			list_del(&pos->cdev_node);
> > +			plist_del(&pos->cdev_node, &pos->cdev->instances);
> > +			mutex_unlock(&cdev->lock);
> >  			mutex_unlock(&tz->lock);
> >  			goto unbind;
> >  		}
> >  	}
> > +	mutex_unlock(&cdev->lock);
> >  	mutex_unlock(&tz->lock);
> >  
> >  	return -ENODEV;
> > @@ -923,7 +927,8 @@ thermal_cooling_device_register(char *type, void *devdata,
> >  	}
> >  
> >  	strcpy(cdev->type, type);
> > -	INIT_LIST_HEAD(&cdev->instances);
> > +	plist_head_init(&cdev->instances);
> > +	mutex_init(&cdev->lock);
> >  	cdev->ops = ops;
> >  	cdev->updated = 1;
> >  	cdev->device.class = &thermal_class;
> > @@ -1019,26 +1024,21 @@ EXPORT_SYMBOL(thermal_cooling_device_unregister);
> >  
> >  static void thermal_zone_do_update(struct thermal_zone_device *tz)
> >  {
> > -	struct thermal_instance *instance1, *instance2;
> > +	struct thermal_instance *instance;
> > +	struct plist_node *node;
> >  	struct thermal_cooling_device *cdev;
> > -	int target;
> >  
> > -	list_for_each_entry(instance1, &tz->instances, tz_node) {
> > -		cdev = instance1->cdev;
> > +	list_for_each_entry(instance, &tz->instances, tz_node) {
> > +		cdev = instance->cdev;
> >  
> >  		/* cooling device has already been updated*/
> >  		if (cdev->updated)
> >  			continue;
> >  
> > -		target = 0;
> > -		/* Make sure cdev enters the deepest cooling state */
> > -		list_for_each_entry(instance2, &cdev->instances, cdev_node) {
> > -			if (instance2->target == -1)
> > -				continue;
> > -			if (instance2->target > target)
> > -				target = instance2->target;
> > -		}
> > -		cdev->ops->set_cur_state(cdev, target);
> > +		/* Deepest cooling state required */
> > +		node = plist_last(&cdev->instances);
> > +
> > +		cdev->ops->set_cur_state(cdev, node->prio < 0 ? 0 : node->prio);
> >  		cdev->updated = 1;
> >  	}
> >  }
> > @@ -1064,7 +1064,7 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
> >  {
> >  	struct thermal_instance *instance;
> >  	struct thermal_cooling_device *cdev = NULL;
> > -	unsigned long cur_state, max_state;
> > +	unsigned long cur_state, max_state, target_state;
> >  	long trip_temp;
> >  	enum thermal_trip_type trip_type;
> >  	enum thermal_trend trend;
> > @@ -1088,21 +1088,29 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
> >  
> >  			cdev->ops->get_cur_state(cdev, &cur_state);
> >  			cdev->ops->get_max_state(cdev, &max_state);
> > -
> > +			target_state = cur_state;
> >  			if (trend == THERMAL_TREND_RAISING) {
> > -				cur_state = cur_state < instance->upper ?
> > +				target_state = cur_state < instance->upper ?
> >  					    (cur_state + 1) : instance->upper;
> >  			} else if (trend == THERMAL_TREND_DROPPING) {
> > -				cur_state = cur_state > instance->lower ?
> > +				target_state = cur_state > instance->lower ?
> >  				    (cur_state - 1) : instance->lower;
> >  			}
> >  
> > +			if (target_state == cur_state)
> > +				continue;
> > +
> >  			/* activate a passive thermal instance */
> >  			if (trip_type == THERMAL_TRIP_PASSIVE &&
> > -			    instance->target == -1)
> > +			    instance->cdev_node.prio == -1)
> >  				tz->passive++;
> >  
> > -			instance->target = cur_state;
> > +			mutex_lock(&cdev->lock);
> > +			plist_del(&instance->cdev_node, &cdev->instances);
> > +			plist_node_init(&instance->cdev_node, target_state);
> > +			plist_add(&instance->cdev_node, &cdev->instances);
> > +			mutex_unlock(&cdev->lock);
> > +
> >  			cdev->updated = 0; /* cooling device needs update */
> >  		}
> >  	} else {	/* below trip */
> > @@ -1111,20 +1119,36 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
> >  				continue;
> >  
> >  			/* Do not use the deacitve thermal instance */
> > -			if (instance->target == -1)
> > +			if (instance->cdev_node.prio == -1)
> >  				continue;
> >  			cdev = instance->cdev;
> >  			cdev->ops->get_cur_state(cdev, &cur_state);
> >  
> > -			cur_state = cur_state > instance->lower ?
> > +			target_state = cur_state > instance->lower ?
> >  				    (cur_state - 1) : -1;
> >  
> > +			if (target_state == cur_state)
> > +				continue;
> > +
> >  			/* deactivate a passive thermal instance */
> >  			if (trip_type == THERMAL_TRIP_PASSIVE &&
> > -			    cur_state == -1)
> > +			    target_state == -1)
> >  				tz->passive--;
> > -			instance->target = cur_state;
> > -			cdev->updated = 0; /* cooling device needs update */
> > +
> > +			mutex_lock(&cdev->lock);
> > +			plist_del(&instance->cdev_node, &cdev->instances);
> > +			plist_node_init(&instance->cdev_node, target_state);
> > +			plist_add(&instance->cdev_node, &cdev->instances);
> > +			mutex_unlock(&cdev->lock);
> > +
> > +			/*
> > +			 * cooling device needs update.
> > +			 * But if the target_state is -1, it means that
> > +			 * the cooling device is already in cooling state 0,
> > +			 * thus we do not need update
> > +			 */
> > +			if (target_state != -1)
> > +				cdev->updated = 0;
> >  		}
> >  	}
> >  
> > diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> > index f725eb9..376a59e 100644
> > --- a/include/linux/thermal.h
> > +++ b/include/linux/thermal.h
> > @@ -28,6 +28,7 @@
> >  #include <linux/idr.h>
> >  #include <linux/device.h>
> >  #include <linux/workqueue.h>
> > +#include <linux/plist.h>
> >  
> >  struct thermal_zone_device;
> >  struct thermal_cooling_device;
> > @@ -93,7 +94,8 @@ struct thermal_cooling_device {
> >  	void *devdata;
> >  	const struct thermal_cooling_device_ops *ops;
> >  	int updated; /* 1 if the cooling device does not need update */
> > -	struct list_head instances;
> > +	struct mutex lock;
> > +	struct plist_head instances;
> >  	struct list_head node;
> >  };
> >  
> > 
> 


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diff mbox

Patch

diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
index a40dda1..9f56250 100644
--- a/drivers/thermal/thermal_sys.c
+++ b/drivers/thermal/thermal_sys.c
@@ -54,11 +54,10 @@  struct thermal_instance {
 	int trip;
 	unsigned long upper;	/* Highest cooling state for this trip point */
 	unsigned long lower;	/* Lowest cooling state for this trip point */
-	unsigned long target;	/* expected cooling state */
 	char attr_name[THERMAL_NAME_LENGTH];
 	struct device_attribute attr;
 	struct list_head tz_node; /* node in tz->instances */
-	struct list_head cdev_node; /* node in cdev->instances */
+	struct plist_node cdev_node; /* node in cdev->instances */
 };
 
 static DEFINE_IDR(thermal_tz_idr);
@@ -787,7 +786,7 @@  int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
 	dev->trip = trip;
 	dev->upper = upper;
 	dev->lower = lower;
-	dev->target = -1;
+	plist_node_init(&dev->cdev_node, -1);
 
 	result = get_idr(&tz->idr, &tz->lock, &dev->id);
 	if (result)
@@ -809,6 +808,7 @@  int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
 		goto remove_symbol_link;
 
 	mutex_lock(&tz->lock);
+	mutex_lock(&cdev->lock);
 	list_for_each_entry(pos, &tz->instances, tz_node)
 	    if (pos->tz == tz && pos->trip == trip && pos->cdev == cdev) {
 		result = -EEXIST;
@@ -816,8 +816,9 @@  int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
 	}
 	if (!result) {
 		list_add_tail(&dev->tz_node, &tz->instances);
-		list_add_tail(&dev->cdev_node, &cdev->instances);
+		plist_add(&dev->cdev_node, &cdev->instances);
 	}
+	mutex_unlock(&cdev->lock);
 	mutex_unlock(&tz->lock);
 
 	if (!result)
@@ -850,14 +851,17 @@  int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
 	struct thermal_instance *pos, *next;
 
 	mutex_lock(&tz->lock);
+	mutex_lock(&cdev->lock);
 	list_for_each_entry_safe(pos, next, &tz->instances, tz_node) {
 		if (pos->tz == tz && pos->trip == trip && pos->cdev == cdev) {
 			list_del(&pos->tz_node);
-			list_del(&pos->cdev_node);
+			plist_del(&pos->cdev_node, &pos->cdev->instances);
+			mutex_unlock(&cdev->lock);
 			mutex_unlock(&tz->lock);
 			goto unbind;
 		}
 	}
+	mutex_unlock(&cdev->lock);
 	mutex_unlock(&tz->lock);
 
 	return -ENODEV;
@@ -923,7 +927,8 @@  thermal_cooling_device_register(char *type, void *devdata,
 	}
 
 	strcpy(cdev->type, type);
-	INIT_LIST_HEAD(&cdev->instances);
+	plist_head_init(&cdev->instances);
+	mutex_init(&cdev->lock);
 	cdev->ops = ops;
 	cdev->updated = 1;
 	cdev->device.class = &thermal_class;
@@ -1019,26 +1024,21 @@  EXPORT_SYMBOL(thermal_cooling_device_unregister);
 
 static void thermal_zone_do_update(struct thermal_zone_device *tz)
 {
-	struct thermal_instance *instance1, *instance2;
+	struct thermal_instance *instance;
+	struct plist_node *node;
 	struct thermal_cooling_device *cdev;
-	int target;
 
-	list_for_each_entry(instance1, &tz->instances, tz_node) {
-		cdev = instance1->cdev;
+	list_for_each_entry(instance, &tz->instances, tz_node) {
+		cdev = instance->cdev;
 
 		/* cooling device has already been updated*/
 		if (cdev->updated)
 			continue;
 
-		target = 0;
-		/* Make sure cdev enters the deepest cooling state */
-		list_for_each_entry(instance2, &cdev->instances, cdev_node) {
-			if (instance2->target == -1)
-				continue;
-			if (instance2->target > target)
-				target = instance2->target;
-		}
-		cdev->ops->set_cur_state(cdev, target);
+		/* Deepest cooling state required */
+		node = plist_last(&cdev->instances);
+
+		cdev->ops->set_cur_state(cdev, node->prio < 0 ? 0 : node->prio);
 		cdev->updated = 1;
 	}
 }
@@ -1064,7 +1064,7 @@  static void thermal_zone_trip_update(struct thermal_zone_device *tz,
 {
 	struct thermal_instance *instance;
 	struct thermal_cooling_device *cdev = NULL;
-	unsigned long cur_state, max_state;
+	unsigned long cur_state, max_state, target_state;
 	long trip_temp;
 	enum thermal_trip_type trip_type;
 	enum thermal_trend trend;
@@ -1088,21 +1088,29 @@  static void thermal_zone_trip_update(struct thermal_zone_device *tz,
 
 			cdev->ops->get_cur_state(cdev, &cur_state);
 			cdev->ops->get_max_state(cdev, &max_state);
-
+			target_state = cur_state;
 			if (trend == THERMAL_TREND_RAISING) {
-				cur_state = cur_state < instance->upper ?
+				target_state = cur_state < instance->upper ?
 					    (cur_state + 1) : instance->upper;
 			} else if (trend == THERMAL_TREND_DROPPING) {
-				cur_state = cur_state > instance->lower ?
+				target_state = cur_state > instance->lower ?
 				    (cur_state - 1) : instance->lower;
 			}
 
+			if (target_state == cur_state)
+				continue;
+
 			/* activate a passive thermal instance */
 			if (trip_type == THERMAL_TRIP_PASSIVE &&
-			    instance->target == -1)
+			    instance->cdev_node.prio == -1)
 				tz->passive++;
 
-			instance->target = cur_state;
+			mutex_lock(&cdev->lock);
+			plist_del(&instance->cdev_node, &cdev->instances);
+			plist_node_init(&instance->cdev_node, target_state);
+			plist_add(&instance->cdev_node, &cdev->instances);
+			mutex_unlock(&cdev->lock);
+
 			cdev->updated = 0; /* cooling device needs update */
 		}
 	} else {	/* below trip */
@@ -1111,20 +1119,36 @@  static void thermal_zone_trip_update(struct thermal_zone_device *tz,
 				continue;
 
 			/* Do not use the deacitve thermal instance */
-			if (instance->target == -1)
+			if (instance->cdev_node.prio == -1)
 				continue;
 			cdev = instance->cdev;
 			cdev->ops->get_cur_state(cdev, &cur_state);
 
-			cur_state = cur_state > instance->lower ?
+			target_state = cur_state > instance->lower ?
 				    (cur_state - 1) : -1;
 
+			if (target_state == cur_state)
+				continue;
+
 			/* deactivate a passive thermal instance */
 			if (trip_type == THERMAL_TRIP_PASSIVE &&
-			    cur_state == -1)
+			    target_state == -1)
 				tz->passive--;
-			instance->target = cur_state;
-			cdev->updated = 0; /* cooling device needs update */
+
+			mutex_lock(&cdev->lock);
+			plist_del(&instance->cdev_node, &cdev->instances);
+			plist_node_init(&instance->cdev_node, target_state);
+			plist_add(&instance->cdev_node, &cdev->instances);
+			mutex_unlock(&cdev->lock);
+
+			/*
+			 * cooling device needs update.
+			 * But if the target_state is -1, it means that
+			 * the cooling device is already in cooling state 0,
+			 * thus we do not need update
+			 */
+			if (target_state != -1)
+				cdev->updated = 0;
 		}
 	}
 
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index f725eb9..376a59e 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -28,6 +28,7 @@ 
 #include <linux/idr.h>
 #include <linux/device.h>
 #include <linux/workqueue.h>
+#include <linux/plist.h>
 
 struct thermal_zone_device;
 struct thermal_cooling_device;
@@ -93,7 +94,8 @@  struct thermal_cooling_device {
 	void *devdata;
 	const struct thermal_cooling_device_ops *ops;
 	int updated; /* 1 if the cooling device does not need update */
-	struct list_head instances;
+	struct mutex lock;
+	struct plist_head instances;
 	struct list_head node;
 };