linux-kernel - [PATCH v1] thermal: trip: Avoid skipping trips in thermal_zone_set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <12509184.O9o76ZdvQC@rjwysocki.net>
Date: Tue, 30 Jul 2024 16:41:18 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>
Subject:
 [PATCH v1] thermal: trip: Avoid skipping trips in thermal_zone_set_trips()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Say there are 3 trip points A, B, C sorted in ascending temperature
order with no hysteresis.  If the zone temerature is exactly equal to
B, thermal_zone_set_trips() will set the boundaries to A and C and the
hardware will not catch any crossing of B (either way) until either A
or C is crossed and the boundaries are changed.

To avoid that, use non-strict inequalities when comparing the trip
threshold to the zone temperature in thermal_zone_set_trips().

In the example above, it will cause both boundaries to be set to B,
which is desirable because an interrupt will trigger when the zone
temperature becomes different from B regardless of which way it goes.
That will allow a new interval to be set depending on the direction of
the zone temperature change.

Fixes: 893bae92237d ("thermal: trip: Make thermal_zone_set_trips() use trip thresholds")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

6.11-rc material.

---
 drivers/thermal/thermal_trip.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-pm/drivers/thermal/thermal_trip.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_trip.c
+++ linux-pm/drivers/thermal/thermal_trip.c
@@ -82,10 +82,10 @@ void thermal_zone_set_trips(struct therm
 		return;

 	for_each_trip_desc(tz, td) {
-		if (td->threshold < tz->temperature && td->threshold > low)
+		if (td->threshold <= tz->temperature && td->threshold > low)
 			low = td->threshold;

-		if (td->threshold > tz->temperature && td->threshold < high)
+		if (td->threshold >= tz->temperature && td->threshold < high)
 			high = td->threshold;
 	}