linux-kernel - [PATCH v1 2/2] thermal: core: Change PM notifier priority to the minimum

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Date: Fri, 14 Jun 2024 17:26:00 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>,
 LKML <linux-kernel@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Zhang Rui <rui.zhang@...el.com>, fhortner@...oo.de
Subject:
 [PATCH v1 2/2] thermal: core: Change PM notifier priority to the minimum

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

It is reported that commit 5a5efdaffda5 ("thermal: core: Resume thermal
zones asynchronously") causes battery data in sysfs on Thinkpad P1 Gen2
to become invalid after a resume from S3 (and it is necessary to reboot
the machine to restore correct battery data).  Some investigation into
the problem indicated that it happened because, after the commit in
question, the ACPI battery PM notifier ran in parallel with
thermal_zone_device_resume() for one of the thermal zones which
apparently confused the platform firmware on the affected system.

While the exact reason for the firmware confusion remains unclear, it
is arguably not particularly relevant, and the expected behavior of the
affected system can be restored by making the thermal PM notifier run
at the lowest priority which avoids interference between work items
spawned by it and the other PM notifiers (that will run before those
work items now).

Fixes: 5a5efdaffda5 ("thermal: core: Resume thermal zones asynchronously")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218881
Reported-by: fhortner@...oo.de
Tested-by: fhortner@...oo.de
Cc: 6.8+ <stable@...r.kernel.org> # 6.8+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/thermal/thermal_core.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-pm/drivers/thermal/thermal_core.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_core.c
+++ linux-pm/drivers/thermal/thermal_core.c
@@ -1710,6 +1710,12 @@ static int thermal_pm_notify(struct noti

 static struct notifier_block thermal_pm_nb = {
 	.notifier_call = thermal_pm_notify,
+	/*
+	 * Run at the lowest priority to avoid interference between the thermal
+	 * zone resume work items spawned by thermal_pm_notify() and the other
+	 * PM notifiers.
+	 */
+	.priority = INT_MIN,
 };

 static int __init thermal_init(void)