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thermal: core: Fix thermal zone suspend-resume synchronization
[ 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>
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2 changed files with 25 additions and 7 deletions
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@ -37,8 +37,6 @@ static LIST_HEAD(thermal_governor_list);
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static DEFINE_MUTEX(thermal_list_lock);
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static DEFINE_MUTEX(thermal_governor_lock);
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static atomic_t in_suspend;
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static struct thermal_governor *def_governor;
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/*
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@ -409,7 +407,7 @@ void __thermal_zone_device_update(struct thermal_zone_device *tz,
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{
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int count;
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if (atomic_read(&in_suspend))
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if (tz->suspended)
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return;
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if (WARN_ONCE(!tz->ops->get_temp,
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@ -1532,17 +1530,35 @@ static int thermal_pm_notify(struct notifier_block *nb,
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case PM_HIBERNATION_PREPARE:
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case PM_RESTORE_PREPARE:
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case PM_SUSPEND_PREPARE:
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atomic_set(&in_suspend, 1);
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mutex_lock(&thermal_list_lock);
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list_for_each_entry(tz, &thermal_tz_list, node) {
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mutex_lock(&tz->lock);
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tz->suspended = true;
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mutex_unlock(&tz->lock);
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}
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mutex_unlock(&thermal_list_lock);
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break;
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case PM_POST_HIBERNATION:
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case PM_POST_RESTORE:
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case PM_POST_SUSPEND:
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atomic_set(&in_suspend, 0);
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mutex_lock(&thermal_list_lock);
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list_for_each_entry(tz, &thermal_tz_list, node) {
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mutex_lock(&tz->lock);
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tz->suspended = false;
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thermal_zone_device_init(tz);
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thermal_zone_device_update(tz,
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THERMAL_EVENT_UNSPECIFIED);
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__thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
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mutex_unlock(&tz->lock);
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}
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mutex_unlock(&thermal_list_lock);
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break;
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default:
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break;
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@ -150,6 +150,7 @@ struct thermal_cooling_device {
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* @node: node in thermal_tz_list (in thermal_core.c)
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* @poll_queue: delayed work for polling
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* @notify_event: Last notification event
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* @suspended: thermal zone suspend indicator
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*/
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struct thermal_zone_device {
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int id;
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@ -183,6 +184,7 @@ struct thermal_zone_device {
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struct list_head node;
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struct delayed_work poll_queue;
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enum thermal_notify_event notify_event;
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bool suspended;
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};
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/**
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