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Message-ID: <b4e077d9-a5f5-47ec-abc7-9e957c32cd5b@kernel.org>
Date: Sat, 28 Jun 2025 11:25:11 +0200
From: Hans de Goede <hansg@...nel.org>
To: Armin Wolf <W_Armin@....de>, sre@...nel.org, hdegoede@...hat.com,
ilpo.jarvinen@...ux.intel.com
Cc: linux-pm@...r.kernel.org, platform-driver-x86@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] power: supply: core: Add
power_supply_get/set_property_direct()
Hi Armin,
On 27-Jun-25 10:51 PM, Armin Wolf wrote:
> Power supply extensions might want to interact with the underlying
> power supply to retrieve data like serial numbers, charging status
> and more. However doing so causes psy->extensions_sem to be locked
> twice, possibly causing a deadlock.
>
> Provide special variants of power_supply_get/set_property() that
> ignore any power supply extensions and thus do not touch the
> associated psy->extensions_sem lock.
>
> Suggested-by: Hans de Goede <hansg@...nel.org>
> Signed-off-by: Armin Wolf <W_Armin@....de>
Thank you for your work on this.
The entire series looks good to me:
Reviewed-by: Hans de Goede <hansg@...nel.org>
for the series.
There is the question of how to merge this. I think it might
be best for the entire series to go through the power-supply
tree.
Ilpo would that work for you and if yes can we have your ack ?
Sebastian, IMHO this should be merged as fixed not as for-next
material.
Regards,
Hans
> ---
> drivers/power/supply/power_supply_core.c | 82 ++++++++++++++++++++----
> include/linux/power_supply.h | 8 +++
> 2 files changed, 78 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
> index aedb20c1d276..e70ffedf1a80 100644
> --- a/drivers/power/supply/power_supply_core.c
> +++ b/drivers/power/supply/power_supply_core.c
> @@ -1241,9 +1241,8 @@ bool power_supply_has_property(struct power_supply *psy,
> return false;
> }
>
> -int power_supply_get_property(struct power_supply *psy,
> - enum power_supply_property psp,
> - union power_supply_propval *val)
> +static int __power_supply_get_property(struct power_supply *psy, enum power_supply_property psp,
> + union power_supply_propval *val, bool use_extensions)
> {
> struct power_supply_ext_registration *reg;
>
> @@ -1253,10 +1252,14 @@ int power_supply_get_property(struct power_supply *psy,
> return -ENODEV;
> }
>
> - scoped_guard(rwsem_read, &psy->extensions_sem) {
> - power_supply_for_each_extension(reg, psy) {
> - if (power_supply_ext_has_property(reg->ext, psp))
> + if (use_extensions) {
> + scoped_guard(rwsem_read, &psy->extensions_sem) {
> + power_supply_for_each_extension(reg, psy) {
> + if (!power_supply_ext_has_property(reg->ext, psp))
> + continue;
> +
> return reg->ext->get_property(psy, reg->ext, reg->data, psp, val);
> + }
> }
> }
>
> @@ -1267,20 +1270,49 @@ int power_supply_get_property(struct power_supply *psy,
> else
> return -EINVAL;
> }
> +
> +int power_supply_get_property(struct power_supply *psy, enum power_supply_property psp,
> + union power_supply_propval *val)
> +{
> + return __power_supply_get_property(psy, psp, val, true);
> +}
> EXPORT_SYMBOL_GPL(power_supply_get_property);
>
> -int power_supply_set_property(struct power_supply *psy,
> - enum power_supply_property psp,
> - const union power_supply_propval *val)
> +/**
> + * power_supply_get_property_direct - Read a power supply property without checking for extensions
> + * @psy: The power supply
> + * @psp: The power supply property to read
> + * @val: The resulting value of the power supply property
> + *
> + * Read a power supply property without taking into account any power supply extensions registered
> + * on the given power supply. This is mostly useful for power supply extensions that want to access
> + * their own power supply as using power_supply_get_property() directly will result in a potential
> + * deadlock.
> + *
> + * Return: 0 on success or negative error code on failure.
> + */
> +int power_supply_get_property_direct(struct power_supply *psy, enum power_supply_property psp,
> + union power_supply_propval *val)
> +{
> + return __power_supply_get_property(psy, psp, val, false);
> +}
> +EXPORT_SYMBOL_GPL(power_supply_get_property_direct);
> +
> +
> +static int __power_supply_set_property(struct power_supply *psy, enum power_supply_property psp,
> + const union power_supply_propval *val, bool use_extensions)
> {
> struct power_supply_ext_registration *reg;
>
> if (atomic_read(&psy->use_cnt) <= 0)
> return -ENODEV;
>
> - scoped_guard(rwsem_read, &psy->extensions_sem) {
> - power_supply_for_each_extension(reg, psy) {
> - if (power_supply_ext_has_property(reg->ext, psp)) {
> + if (use_extensions) {
> + scoped_guard(rwsem_read, &psy->extensions_sem) {
> + power_supply_for_each_extension(reg, psy) {
> + if (!power_supply_ext_has_property(reg->ext, psp))
> + continue;
> +
> if (reg->ext->set_property)
> return reg->ext->set_property(psy, reg->ext, reg->data,
> psp, val);
> @@ -1295,8 +1327,34 @@ int power_supply_set_property(struct power_supply *psy,
>
> return psy->desc->set_property(psy, psp, val);
> }
> +
> +int power_supply_set_property(struct power_supply *psy, enum power_supply_property psp,
> + const union power_supply_propval *val)
> +{
> + return __power_supply_set_property(psy, psp, val, true);
> +}
> EXPORT_SYMBOL_GPL(power_supply_set_property);
>
> +/**
> + * power_supply_set_property_direct - Write a power supply property without checking for extensions
> + * @psy: The power supply
> + * @psp: The power supply property to write
> + * @val: The value to write to the power supply property
> + *
> + * Write a power supply property without taking into account any power supply extensions registered
> + * on the given power supply. This is mostly useful for power supply extensions that want to access
> + * their own power supply as using power_supply_set_property() directly will result in a potential
> + * deadlock.
> + *
> + * Return: 0 on success or negative error code on failure.
> + */
> +int power_supply_set_property_direct(struct power_supply *psy, enum power_supply_property psp,
> + const union power_supply_propval *val)
> +{
> + return __power_supply_set_property(psy, psp, val, false);
> +}
> +EXPORT_SYMBOL_GPL(power_supply_set_property_direct);
> +
> int power_supply_property_is_writeable(struct power_supply *psy,
> enum power_supply_property psp)
> {
> diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
> index 45468959dd98..f21f806bfb38 100644
> --- a/include/linux/power_supply.h
> +++ b/include/linux/power_supply.h
> @@ -878,15 +878,23 @@ static inline int power_supply_is_system_supplied(void) { return -ENOSYS; }
> extern int power_supply_get_property(struct power_supply *psy,
> enum power_supply_property psp,
> union power_supply_propval *val);
> +int power_supply_get_property_direct(struct power_supply *psy, enum power_supply_property psp,
> + union power_supply_propval *val);
> #if IS_ENABLED(CONFIG_POWER_SUPPLY)
> extern int power_supply_set_property(struct power_supply *psy,
> enum power_supply_property psp,
> const union power_supply_propval *val);
> +int power_supply_set_property_direct(struct power_supply *psy, enum power_supply_property psp,
> + const union power_supply_propval *val);
> #else
> static inline int power_supply_set_property(struct power_supply *psy,
> enum power_supply_property psp,
> const union power_supply_propval *val)
> { return 0; }
> +static inline int power_supply_set_property_direct(struct power_supply *psy,
> + enum power_supply_property psp,
> + const union power_supply_propval *val)
> +{ return 0; }
> #endif
> extern void power_supply_external_power_changed(struct power_supply *psy);
>
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