From fcecef9a84f689631074240d63f4e00c4c94a614 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Mon, 18 Dec 2023 20:25:02 +0100 Subject: 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 Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin --- include/linux/thermal.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/thermal.h') 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; }; /** -- cgit v1.2.3