Re: [PATCH v2 3/4] thermal: core: Introduce thermal_cooling_device_update()

Zhang, Rui
2023-03-14T02:03:49Z

On Mon, 2023-03-13 at 15:32 +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Introduce a core thermal API function,
> thermal_cooling_device_update(),
> for updating the max_state value for a cooling device and rearranging
> its statistics in sysfs after a possible change of its
> ->get_max_state()
> callback return value.
>
> That callback is now invoked only once, during cooling device
> registration, to populate the max_state field in the cooling device
> object, so if its return value changes, it needs to be invoked again
> and the new return value needs to be stored as max_state. Moreover,
> the statistics presented in sysfs need to be rearranged in general,
> because there may not be enough room in them to store data for all
> of the possible states (in the case when max_state grows).
>
> The new function takes care of that (and some other minor things
> related to it), but some extra locking and lockdep annotations are
> added in several places too to protect against crashes in the cases
> when the statistics are not present or when a stale max_state value
> might be used by sysfs attributes.
>
> Note that the actual user of the new function will be added
> separately.
>
> Link:
> https://lore.kernel.org/linux-pm/53ec1f06f61c984100868926f282647e57ecfb2d.camel@intel.com/
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Tested-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Zhang Rui <rui.zhang@intel.com>

thanks,
rui

> ---
>
> v1 -> v2:
> * Make thermal_cooling_device_update() do the full
> IS_ERR_OR_NULL() check
> on cdev, so that its callers don't need to do it.
> * Remove ->set_cur_state() callback invocation from
> thermal_cooling_device_update(), because it is redundant (and
> it doesn't
> make sense to pass a state value exceeding max_state to it
> anyway).
>
> ---
> drivers/thermal/thermal_core.c | 40 ++++++++++++++++++++++
> drivers/thermal/thermal_core.h | 1
> drivers/thermal/thermal_sysfs.c | 72
> +++++++++++++++++++++++++++++++++++-----
> include/linux/thermal.h | 1
> 4 files changed, 106 insertions(+), 8 deletions(-)
>
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -1057,6 +1057,46 @@ static bool thermal_cooling_device_prese
> return false;
> }
>
> +void thermal_cooling_device_update(struct thermal_cooling_device
> *cdev)
> +{
> + unsigned long state;
> +
> + if (IS_ERR_OR_NULL(cdev))
> + return;
> +
> + /*
> + * Hold thermal_list_lock throughout the update to prevent the
> device
> + * from going away while being updated.
> + */
> + mutex_lock(&thermal_list_lock);
> +
> + if (!thermal_cooling_device_present(cdev))
> + goto unlock_list;
> +
> + /*
> + * Update under the cdev lock to prevent the state from being
> set beyond
> + * the new limit concurrently.
> + */
> + mutex_lock(&cdev->lock);
> +
> + if (cdev->ops->get_max_state(cdev, &cdev->max_state))
> + goto unlock;
> +
> + thermal_cooling_device_stats_reinit(cdev);
> +
> + if (cdev->ops->get_cur_state(cdev, &state) || state > cdev-
> >max_state)
> + goto unlock;
> +
> + thermal_cooling_device_stats_update(cdev, state);
> +
> +unlock:
> + mutex_unlock(&cdev->lock);
> +
> +unlock_list:
> + mutex_unlock(&thermal_list_lock);
> +}
> +EXPORT_SYMBOL_GPL(thermal_cooling_device_update);
> +
> static void __unbind(struct thermal_zone_device *tz, int mask,
> struct thermal_cooling_device *cdev)
> {
> Index: linux-pm/drivers/thermal/thermal_sysfs.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_sysfs.c
> +++ linux-pm/drivers/thermal/thermal_sysfs.c
> @@ -685,6 +685,8 @@ void thermal_cooling_device_stats_update
> {
> struct cooling_dev_stats *stats = cdev->stats;
>
> + lockdep_assert_held(&cdev->lock);
> +
> if (!stats)
> return;
>
> @@ -706,13 +708,22 @@ static ssize_t total_trans_show(struct d
> struct device_attribute *attr, char
> *buf)
> {
> struct thermal_cooling_device *cdev = to_cooling_device(dev);
> - struct cooling_dev_stats *stats = cdev->stats;
> + struct cooling_dev_stats *stats;
> int ret;
>
> + mutex_lock(&cdev->lock);
> +
> + stats = cdev->stats;
> + if (!stats)
> + goto unlock;
> +
> spin_lock(&stats->lock);
> ret = sprintf(buf, "%u\n", stats->total_trans);
> spin_unlock(&stats->lock);
>
> +unlock:
> + mutex_unlock(&cdev->lock);
> +
> return ret;
> }
>
> @@ -721,11 +732,18 @@ time_in_state_ms_show(struct device *dev
> char *buf)
> {
> struct thermal_cooling_device *cdev = to_cooling_device(dev);
> - struct cooling_dev_stats *stats = cdev->stats;
> + struct cooling_dev_stats *stats;
> ssize_t len = 0;
> int i;
>
> + mutex_lock(&cdev->lock);
> +
> + stats = cdev->stats;
> + if (!stats)
> + goto unlock;
> +
> spin_lock(&stats->lock);
> +
> update_time_in_state(stats);
>
> for (i = 0; i <= cdev->max_state; i++) {
> @@ -734,6 +752,9 @@ time_in_state_ms_show(struct device *dev
> }
> spin_unlock(&stats->lock);
>
> +unlock:
> + mutex_unlock(&cdev->lock);
> +
> return len;
> }
>
> @@ -742,8 +763,16 @@ reset_store(struct device *dev, struct d
> size_t count)
> {
> struct thermal_cooling_device *cdev = to_cooling_device(dev);
> - struct cooling_dev_stats *stats = cdev->stats;
> - int i, states = cdev->max_state + 1;
> + struct cooling_dev_stats *stats;
> + int i, states;
> +
> + mutex_lock(&cdev->lock);
> +
> + stats = cdev->stats;
> + if (!stats)
> + goto unlock;
> +
> + states = cdev->max_state + 1;
>
> spin_lock(&stats->lock);
>
> @@ -757,6 +786,9 @@ reset_store(struct device *dev, struct d
>
> spin_unlock(&stats->lock);
>
> +unlock:
> + mutex_unlock(&cdev->lock);
> +
> return count;
> }
>
> @@ -764,10 +796,18 @@ static ssize_t trans_table_show(struct d
> struct device_attribute *attr, char
> *buf)
> {
> struct thermal_cooling_device *cdev = to_cooling_device(dev);
> - struct cooling_dev_stats *stats = cdev->stats;
> + struct cooling_dev_stats *stats;
> ssize_t len = 0;
> int i, j;
>
> + mutex_lock(&cdev->lock);
> +
> + stats = cdev->stats;
> + if (!stats) {
> + len = -ENODATA;
> + goto unlock;
> + }
> +
> len += snprintf(buf + len, PAGE_SIZE - len, "
> From : To\n");
> len += snprintf(buf + len, PAGE_SIZE - len, " : ");
> for (i = 0; i <= cdev->max_state; i++) {
> @@ -775,8 +815,10 @@ static ssize_t trans_table_show(struct d
> break;
> len += snprintf(buf + len, PAGE_SIZE - len,
> "state%2u ", i);
> }
> - if (len >= PAGE_SIZE)
> - return PAGE_SIZE;
> + if (len >= PAGE_SIZE) {
> + len = PAGE_SIZE;
> + goto unlock;
> + }
>
> len += snprintf(buf + len, PAGE_SIZE - len, "\n");
>
> @@ -799,8 +841,12 @@ static ssize_t trans_table_show(struct d
>
> if (len >= PAGE_SIZE) {
> pr_warn_once("Thermal transition table exceeds
> PAGE_SIZE. Disabling\n");
> - return -EFBIG;
> + len = -EFBIG;
> }
> +
> +unlock:
> + mutex_unlock(&cdev->lock);
> +
> return len;
> }
>
> @@ -830,6 +876,8 @@ static void cooling_device_stats_setup(s
> unsigned long states = cdev->max_state + 1;
> int var;
>
> + lockdep_assert_held(&cdev->lock);
> +
> var = sizeof(*stats);
> var += sizeof(*stats->time_in_state) * states;
> var += sizeof(*stats->trans_table) * states * states;
> @@ -855,6 +903,8 @@ out:
>
> static void cooling_device_stats_destroy(struct
> thermal_cooling_device *cdev)
> {
> + lockdep_assert_held(&cdev->lock);
> +
> kfree(cdev->stats);
> cdev->stats = NULL;
> }
> @@ -879,6 +929,12 @@ void thermal_cooling_device_destroy_sysf
> cooling_device_stats_destroy(cdev);
> }
>
> +void thermal_cooling_device_stats_reinit(struct
> thermal_cooling_device *cdev)
> +{
> + cooling_device_stats_destroy(cdev);
> + cooling_device_stats_setup(cdev);
> +}
> +
> /* these helper will be used only at the time of bindig */
> ssize_t
> trip_point_show(struct device *dev, struct device_attribute *attr,
> char *buf)
> Index: linux-pm/drivers/thermal/thermal_core.h
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.h
> +++ linux-pm/drivers/thermal/thermal_core.h
> @@ -127,6 +127,7 @@ int thermal_zone_create_device_groups(st
> void thermal_zone_destroy_device_groups(struct thermal_zone_device
> *);
> void thermal_cooling_device_setup_sysfs(struct
> thermal_cooling_device *);
> void thermal_cooling_device_destroy_sysfs(struct
> thermal_cooling_device *cdev);
> +void thermal_cooling_device_stats_reinit(struct
> thermal_cooling_device *cdev);
> /* used only at binding time */
> ssize_t trip_point_show(struct device *, struct device_attribute *,
> char *);
> ssize_t weight_show(struct device *, struct device_attribute *, char
> *);
> Index: linux-pm/include/linux/thermal.h
> ===================================================================
> --- linux-pm.orig/include/linux/thermal.h
> +++ linux-pm/include/linux/thermal.h
> @@ -388,6 +388,7 @@ devm_thermal_of_cooling_device_register(
> struct device_node *np,
> char *type, void *devdata,
> const struct thermal_cooling_device_ops
> *ops);
> +void thermal_cooling_device_update(struct thermal_cooling_device *);
> void thermal_cooling_device_unregister(struct thermal_cooling_device
> *);
> struct thermal_zone_device *thermal_zone_get_zone_by_name(const char
> *name);
> int thermal_zone_get_temp(struct thermal_zone_device *tz, int
> *temp);
>
>
>