From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com
[ 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/ Reported-by: Bo Ye bo.ye@mediatek.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com 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 e6f3166a9208..86ec48c1af93 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;
/* @@ -409,7 +407,7 @@ void __thermal_zone_device_update(struct thermal_zone_device *tz, { int count;
- if (atomic_read(&in_suspend)) + if (tz->suspended) return;
if (WARN_ONCE(!tz->ops->get_temp, @@ -1528,17 +1526,35 @@ 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 a5ae4af955ff..4012f440bfdc 100644 --- a/include/linux/thermal.h +++ b/include/linux/thermal.h @@ -150,6 +150,7 @@ 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; @@ -183,6 +184,7 @@ struct thermal_zone_device { struct list_head node; struct delayed_work poll_queue; enum thermal_notify_event notify_event; + bool suspended; };
/**