Messages in this thread Patch in this message | | | From | "Rafael J. Wysocki" <> | Subject | [PATCH v1 4/6] thermal: trip: Use READ_ONCE() for lockless access to trip properties | Date | Fri, 10 May 2024 16:18:19 +0200 |
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
When accessing trip temperature and hysteresis without locking, it is better to use READ_ONCE() to prevent compiler optimizations possibly affecting the read from being applied.
Of course, for the READ_ONCE() to be effective, WRITE_ONCE() needs to be used when updating their values.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> --- drivers/thermal/thermal_sysfs.c | 6 +++--- drivers/thermal/thermal_trip.c | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-)
Index: linux-pm/drivers/thermal/thermal_sysfs.c =================================================================== --- linux-pm.orig/drivers/thermal/thermal_sysfs.c +++ linux-pm/drivers/thermal/thermal_sysfs.c @@ -141,7 +141,7 @@ trip_point_temp_show(struct device *dev, if (sscanf(attr->attr.name, "trip_point_%d_temp", &trip_id) != 1) return -EINVAL; - return sprintf(buf, "%d\n", tz->trips[trip_id].trip.temperature); + return sprintf(buf, "%d\n", READ_ONCE(tz->trips[trip_id].trip.temperature)); } static ssize_t @@ -165,7 +165,7 @@ trip_point_hyst_store(struct device *dev trip = &tz->trips[trip_id].trip; if (hyst != trip->hysteresis) { - trip->hysteresis = hyst; + WRITE_ONCE(trip->hysteresis, hyst); thermal_zone_trip_updated(tz, trip); } @@ -185,7 +185,7 @@ trip_point_hyst_show(struct device *dev, if (sscanf(attr->attr.name, "trip_point_%d_hyst", &trip_id) != 1) return -EINVAL; - return sprintf(buf, "%d\n", tz->trips[trip_id].trip.hysteresis); + return sprintf(buf, "%d\n", READ_ONCE(tz->trips[trip_id].trip.hysteresis)); } static ssize_t Index: linux-pm/drivers/thermal/thermal_trip.c =================================================================== --- linux-pm.orig/drivers/thermal/thermal_trip.c +++ linux-pm/drivers/thermal/thermal_trip.c @@ -161,7 +161,7 @@ void thermal_zone_set_trip_temp(struct t if (trip->temperature == temp) return; - trip->temperature = temp; + WRITE_ONCE(trip->temperature, temp); thermal_notify_tz_trip_change(tz, trip); } EXPORT_SYMBOL_GPL(thermal_zone_set_trip_temp);
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