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Message-ID: <2fe5274b-b6ea-4c70-9896-8ae6aa99e174@arm.com>
Date: Thu, 5 Sep 2024 10:02:51 +0100
From: Lukasz Luba <lukasz.luba@....com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: LKML <linux-kernel@...r.kernel.org>, Zhang Rui <rui.zhang@...el.com>,
Linux PM <linux-pm@...r.kernel.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v2] thermal: sysfs: Add sanity checks for trip temperature
and hysteresis
On 8/26/24 17:21, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Add sanity checks for new trip temperature and hysteresis values to
> trip_point_temp_store() and trip_point_hyst_store() to prevent trip
> point threshold from falling below THERMAL_TEMP_INVALID.
>
> However, still allow user space to pass THERMAL_TEMP_INVALID as the
> new trip temperature value to invalidate the trip if necessary.
>
> Also allow the hysteresis to be updated when the temperature is invalid
> to allow user space to avoid having to adjust hysteresis after a valid
> temperature has been set, but in that case just change the value and do
> nothing else.
>
> Fixes: be0a3600aa1e ("thermal: sysfs: Rework the handling of trip point updates")
> Cc: 6.8+ <stable@...r.kernel.org> # 6.8+
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>
> v1 -> v2:
> * Reorder the new check in trip_point_hyst_store() to be easier
> to read (Daniel).
> * Add a comment explaining the ordering of the new check in
> trip_point_temp_store().
> * Allow the hysteresis to be updated when the temperature is invalid.
>
> This is an update of
>
> https://lore.kernel.org/linux-pm/7719509.EvYhyI6sBW@rjwysocki.net/
>
> which is being sent separately because patch [1/2] from the original series
> has been applied.
>
> ---
> drivers/thermal/thermal_sysfs.c | 50 ++++++++++++++++++++++++++++++----------
> 1 file changed, 38 insertions(+), 12 deletions(-)
>
> Index: linux-pm/drivers/thermal/thermal_sysfs.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_sysfs.c
> +++ linux-pm/drivers/thermal/thermal_sysfs.c
> @@ -111,18 +111,26 @@ trip_point_temp_store(struct device *dev
>
> mutex_lock(&tz->lock);
>
> - if (temp != trip->temperature) {
> - if (tz->ops.set_trip_temp) {
> - ret = tz->ops.set_trip_temp(tz, trip, temp);
> - if (ret)
> - goto unlock;
> - }
> + if (temp == trip->temperature)
> + goto unlock;
>
> - thermal_zone_set_trip_temp(tz, trip, temp);
> + /* Arrange the condition to avoid integer overflows. */
> + if (temp != THERMAL_TEMP_INVALID &&
> + temp <= trip->hysteresis + THERMAL_TEMP_INVALID) {
> + ret = -EINVAL;
> + goto unlock;
> + }
>
> - __thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
> + if (tz->ops.set_trip_temp) {
> + ret = tz->ops.set_trip_temp(tz, trip, temp);
> + if (ret)
> + goto unlock;
> }
>
> + thermal_zone_set_trip_temp(tz, trip, temp);
> +
> + __thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
> +
> unlock:
> mutex_unlock(&tz->lock);
>
> @@ -152,15 +160,33 @@ trip_point_hyst_store(struct device *dev
>
> mutex_lock(&tz->lock);
>
> - if (hyst != trip->hysteresis) {
> - thermal_zone_set_trip_hyst(tz, trip, hyst);
> + if (hyst == trip->hysteresis)
> + goto unlock;
> +
> + /*
> + * Allow the hysteresis to be updated when the temperature is invalid
> + * to allow user space to avoid having to adjust hysteresis after a
> + * valid temperature has been set, but in that case just change the
> + * value and do nothing else.
> + */
> + if (trip->temperature == THERMAL_TEMP_INVALID) {
> + WRITE_ONCE(trip->hysteresis, hyst);
> + goto unlock;
> + }
>
> - __thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
> + if (trip->temperature - hyst <= THERMAL_TEMP_INVALID) {
> + ret = -EINVAL;
> + goto unlock;
> }
>
> + thermal_zone_set_trip_hyst(tz, trip, hyst);
> +
> + __thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
> +
> +unlock:
> mutex_unlock(&tz->lock);
>
> - return count;
> + return ret ? ret : count;
> }
>
> static ssize_t
>
>
>
Reviewed-by: Lukasz Luba <lukasz.luba@....com>
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