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Message-ID: <eafd7c9056ab3d691cafe2db136135abd2d7ed81.camel@intel.com>
Date: Tue, 20 Aug 2024 07:05:51 +0000
From: "Zhang, Rui" <rui.zhang@...el.com>
To: "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, "rjw@...ysocki.net"
<rjw@...ysocki.net>
CC: "lukasz.luba@....com" <lukasz.luba@....com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v3 05/14] thermal: core: Move thermal zone locking out of
bind/unbind functions
On Mon, 2024-08-19 at 17:58 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Since thermal_bind_cdev_to_trip() and thermal_unbind_cdev_from_trip()
> acquire the thermal zone lock, the locking rules for their callers
> get
> complicated. In particular, the thermal zone lock cannot be acquired
> in any code path leading to one of these functions even though it
> might
> be useful to do so.
>
> To address this, remove the thermal zone locking from both these
> functions, add lockdep assertions for the thermal zone lock to both
> of them and make their callers acquire the thermal zone lock instead.
>
> No intentional functional impact.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Reviewed-by: Zhang Rui <rui.zhang@...el.com>
thanks,
rui
> ---
>
> v2 -> v3: Rebase after dropping patches [04-05/17] from the series
>
> v1 -> v2: No changes
>
> ---
> drivers/acpi/thermal.c | 2 +-
> drivers/thermal/thermal_core.c | 30 ++++++++++++++++++++++--------
> 2 files changed, 23 insertions(+), 9 deletions(-)
>
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -785,6 +785,7 @@ int thermal_bind_cdev_to_trip(struct the
> int result;
>
> lockdep_assert_held(&thermal_list_lock);
> + lockdep_assert_held(&tz->lock);
>
> if (list_empty(&tz->node) || list_empty(&cdev->node))
> return -EINVAL;
> @@ -847,7 +848,6 @@ int thermal_bind_cdev_to_trip(struct the
> if (result)
> goto remove_trip_file;
>
> - mutex_lock(&tz->lock);
> mutex_lock(&cdev->lock);
> list_for_each_entry(pos, &tz->thermal_instances, tz_node)
> if (pos->trip == trip && pos->cdev == cdev) {
> @@ -862,7 +862,6 @@ int thermal_bind_cdev_to_trip(struct the
> thermal_governor_update_tz(tz, THERMAL_TZ_BIND_CDEV);
> }
> mutex_unlock(&cdev->lock);
> - mutex_unlock(&tz->lock);
>
> if (!result)
> return 0;
> @@ -886,11 +885,19 @@ int thermal_zone_bind_cooling_device(str
> unsigned long upper, unsigned
> long lower,
> unsigned int weight)
> {
> + int ret;
> +
> if (trip_index < 0 || trip_index >= tz->num_trips)
> return -EINVAL;
>
> - return thermal_bind_cdev_to_trip(tz, &tz-
> >trips[trip_index].trip, cdev,
> - upper, lower, weight);
> + mutex_lock(&tz->lock);
> +
> + ret = thermal_bind_cdev_to_trip(tz, &tz-
> >trips[trip_index].trip, cdev,
> + upper, lower, weight);
> +
> + mutex_unlock(&tz->lock);
> +
> + return ret;
> }
> EXPORT_SYMBOL_GPL(thermal_zone_bind_cooling_device);
>
> @@ -912,7 +919,8 @@ int thermal_unbind_cdev_from_trip(struct
> {
> struct thermal_instance *pos, *next;
>
> - mutex_lock(&tz->lock);
> + lockdep_assert_held(&tz->lock);
> +
> mutex_lock(&cdev->lock);
> list_for_each_entry_safe(pos, next, &tz->thermal_instances,
> tz_node) {
> if (pos->trip == trip && pos->cdev == cdev) {
> @@ -922,12 +930,10 @@ int thermal_unbind_cdev_from_trip(struct
> thermal_governor_update_tz(tz,
> THERMAL_TZ_UNBIND_CDEV);
>
> mutex_unlock(&cdev->lock);
> - mutex_unlock(&tz->lock);
> goto unbind;
> }
> }
> mutex_unlock(&cdev->lock);
> - mutex_unlock(&tz->lock);
>
> return -ENODEV;
>
> @@ -945,10 +951,18 @@ int thermal_zone_unbind_cooling_device(s
> int trip_index,
> struct thermal_cooling_device
> *cdev)
> {
> + int ret;
> +
> if (trip_index < 0 || trip_index >= tz->num_trips)
> return -EINVAL;
>
> - return thermal_unbind_cdev_from_trip(tz, &tz-
> >trips[trip_index].trip, cdev);
> + mutex_lock(&tz->lock);
> +
> + ret = thermal_unbind_cdev_from_trip(tz, &tz-
> >trips[trip_index].trip, cdev);
> +
> + mutex_unlock(&tz->lock);
> +
> + return ret;
> }
> EXPORT_SYMBOL_GPL(thermal_zone_unbind_cooling_device);
>
> Index: linux-pm/drivers/acpi/thermal.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/thermal.c
> +++ linux-pm/drivers/acpi/thermal.c
> @@ -609,7 +609,7 @@ static int acpi_thermal_bind_unbind_cdev
> .thermal = thermal, .cdev = cdev, .bind = bind
> };
>
> - return for_each_thermal_trip(thermal, bind_unbind_cdev_cb,
> &bd);
> + return thermal_zone_for_each_trip(thermal,
> bind_unbind_cdev_cb, &bd);
> }
>
> static int
>
>
>
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