2024-05-10 14:21:56

by Rafael J. Wysocki

Subject: [PATCH v1 0/6] thermal: core: Assorted improvements for v6.11

Hi Everyone,

This series is for the 6.11 cycle, but since it is ready from my POV,
here it goes in case people have the time to look at it in the meantime.

The patches in the series address some shortcomings in the thermal
core code (including the Bang-Bang governor) and clean it up somewhat.

Please refer to the individual patch changelogs for details.

This series is independent of the thermal debugfs one posted yesterday:

https://lore.kernel.org/linux-pm/12438864.O9o76ZdvQC@kreacher/

At one point I'm going to put this series on a git branch for easier
access/testing.

Thanks!

2024-05-10 14:23:51

by Rafael J. Wysocki

Subject: [PATCH v1 4/6] thermal: trip: Use READ_ONCE() for lockless access to trip properties

From: Rafael J. Wysocki <[email protected]>

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 <[email protected]>
---
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);