[PATCH v3 5/5] platform/x86: hp-wmi: add locking for concurrent hwmon access

Emre Cecanpunar
2026-04-05T14:45:22Z

hp_wmi_hwmon_priv.mode and .pwm are written by hp_wmi_hwmon_write() in
sysfs context and read by hp_wmi_hwmon_keep_alive_handler() in a
workqueue. A concurrent write and keep-alive expiry can observe an
inconsistent mode/pwm pair (e.g. mode=MANUAL with a stale pwm).

Add a mutex to hp_wmi_hwmon_priv protecting mode and pwm. Hold it in
hp_wmi_hwmon_write() across the field update and apply call, and in
hp_wmi_hwmon_keep_alive_handler() before calling apply.

In hp_wmi_hwmon_read(), only the pwm_enable path reads priv->mode; use
scoped_guard() there to avoid holding the lock across unrelated WMI
calls.

Fixes: c203c59fb5de ("platform/x86: hp-wmi: implement fan keep-alive")
Signed-off-by: Emre Cecanpunar <emreleno@gmail.com>
---
drivers/platform/x86/hp/hp-wmi.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/hp/hp-wmi.c b/drivers/platform/x86/hp/hp-wmi.c
index db72ad9da0a5..1096fb46cbcd 100644
--- a/drivers/platform/x86/hp/hp-wmi.c
+++ b/drivers/platform/x86/hp/hp-wmi.c
@@ -453,6 +453,7 @@ enum pwm_modes {
};

struct hp_wmi_hwmon_priv {
+ struct mutex lock; /* protects mode, pwm */
u8 min_rpm;
u8 max_rpm;
int gpu_delta;
@@ -2422,6 +2423,7 @@ static int hp_wmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
{
struct hp_wmi_hwmon_priv *priv;
int rpm, ret;
+ u8 mode;

priv = dev_get_drvdata(dev);
switch (type) {
@@ -2445,11 +2447,13 @@ static int hp_wmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
*val = rpm_to_pwm(rpm / 100, priv);
return 0;
}
- switch (priv->mode) {
+ scoped_guard(mutex, &priv->lock)
+ mode = priv->mode;
+ switch (mode) {
case PWM_MODE_MAX:
case PWM_MODE_MANUAL:
case PWM_MODE_AUTO:
- *val = priv->mode;
+ *val = mode;
return 0;
default:
/* shouldn't happen */
@@ -2467,6 +2471,7 @@ static int hp_wmi_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
int rpm;

priv = dev_get_drvdata(dev);
+ guard(mutex)(&priv->lock);
switch (type) {
case hwmon_pwm:
if (attr == hwmon_pwm_input) {
@@ -2535,6 +2540,8 @@ static void hp_wmi_hwmon_keep_alive_handler(struct work_struct *work)

dwork = to_delayed_work(work);
priv = container_of(dwork, struct hp_wmi_hwmon_priv, keep_alive_dwork);
+
+ guard(mutex)(&priv->lock);
/*
* Re-apply the current hwmon context settings.
* NOTE: hp_wmi_apply_fan_settings will handle the re-scheduling.
@@ -2592,6 +2599,8 @@ static int hp_wmi_hwmon_init(void)
if (!priv)
return -ENOMEM;

+ mutex_init(&priv->lock);
+
ret = hp_wmi_setup_fan_settings(priv);
if (ret)
return ret;
--
2.53.0