[PATCH AUTOSEL 6.7 18/18] thermal: core: Fix thermal zone suspend-resume synchronization
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DORMANTno replies
From: Sasha Levin <sashal@kernel.org>
Date: 2024-01-16 00:13:40
Also in:
linux-mediatek, linux-pm, lkml, stable
Subsystem:
the rest, thermal · Maintainers:
Linus Torvalds, Rafael J. Wysocki, Daniel Lezcano
From: "Rafael J. Wysocki" <redacted>
[ Upstream commit 4e814173a8c4f432fd068b1c796f0416328c9d99 ]
There are 3 synchronization issues with thermal zone suspend-resume
during system-wide transitions:
1. The resume code runs in a PM notifier which is invoked after user
space has been thawed, so it can run concurrently with user space
which can trigger a thermal zone device removal. If that happens,
the thermal zone resume code may use a stale pointer to the next
list element and crash, because it does not hold thermal_list_lock
while walking thermal_tz_list.
2. The thermal zone resume code calls thermal_zone_device_init()
outside the zone lock, so user space or an update triggered by
the platform firmware may see an inconsistent state of a
thermal zone leading to unexpected behavior.
3. Clearing the in_suspend global variable in thermal_pm_notify()
allows __thermal_zone_device_update() to continue for all thermal
zones and it may as well run before the thermal_tz_list walk (or
at any point during the list walk for that matter) and attempt to
operate on a thermal zone that has not been resumed yet. It may
also race destructively with thermal_zone_device_init().
To address these issues, add thermal_list_lock locking to
thermal_pm_notify(), especially arount the thermal_tz_list,
make it call thermal_zone_device_init() back-to-back with
__thermal_zone_device_update() under the zone lock and replace
in_suspend with per-zone bool "suspend" indicators set and unset
under the given zone's lock.
Link: https://lore.kernel.org/linux-pm/20231218162348.69101-1-bo.ye@mediatek.com/ (local)
Reported-by: Bo Ye <redacted>
Signed-off-by: Rafael J. Wysocki <redacted>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/thermal/thermal_core.c | 30 +++++++++++++++++++++++-------
include/linux/thermal.h | 2 ++
2 files changed, 25 insertions(+), 7 deletions(-)
diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 9c17d35ccbbd..fe3bcfba4d67 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c@@ -37,8 +37,6 @@ static LIST_HEAD(thermal_governor_list); static DEFINE_MUTEX(thermal_list_lock); static DEFINE_MUTEX(thermal_governor_lock); -static atomic_t in_suspend; - static struct thermal_governor *def_governor; /*
@@ -405,7 +403,7 @@ void __thermal_zone_device_update(struct thermal_zone_device *tz, { const struct thermal_trip *trip; - if (atomic_read(&in_suspend)) + if (tz->suspended) return; if (WARN_ONCE(!tz->ops->get_temp,
@@ -1515,17 +1513,35 @@ static int thermal_pm_notify(struct notifier_block *nb, case PM_HIBERNATION_PREPARE: case PM_RESTORE_PREPARE: case PM_SUSPEND_PREPARE: - atomic_set(&in_suspend, 1); + mutex_lock(&thermal_list_lock); + + list_for_each_entry(tz, &thermal_tz_list, node) { + mutex_lock(&tz->lock); + + tz->suspended = true; + + mutex_unlock(&tz->lock); + } + + mutex_unlock(&thermal_list_lock); break; case PM_POST_HIBERNATION: case PM_POST_RESTORE: case PM_POST_SUSPEND: - atomic_set(&in_suspend, 0); + mutex_lock(&thermal_list_lock); + list_for_each_entry(tz, &thermal_tz_list, node) { + mutex_lock(&tz->lock); + + tz->suspended = false; + thermal_zone_device_init(tz); - thermal_zone_device_update(tz, - THERMAL_EVENT_UNSPECIFIED); + __thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED); + + mutex_unlock(&tz->lock); } + + mutex_unlock(&thermal_list_lock); break; default: break;
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index cee814d5d1ac..1da1739d75d9 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h@@ -149,6 +149,7 @@ struct thermal_cooling_device { * @node: node in thermal_tz_list (in thermal_core.c) * @poll_queue: delayed work for polling * @notify_event: Last notification event + * @suspended: thermal zone suspend indicator */ struct thermal_zone_device { int id;
@@ -181,6 +182,7 @@ struct thermal_zone_device { struct list_head node; struct delayed_work poll_queue; enum thermal_notify_event notify_event; + bool suspended; }; /**
--
2.43.0
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