Patch "thermal: power_allocator: fix one race condition issue for thermal_instances list" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

thermal: power_allocator: fix one race condition issue for thermal_instances list

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
thermal-power_allocator-fix-one-race-condition-issue-for-thermal_instances-list.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Yi Zeng <[email protected]>
Date: Tue, 26 Dec 2017 19:22:26 +0800
Subject: thermal: power_allocator: fix one race condition issue for thermal_instances list

From: Yi Zeng <[email protected]>

[ Upstream commit a5de11d67dcd268b8d0beb73dc374de5e97f0caf ]

When invoking allow_maximum_power and traverse tz->thermal_instances, we should grab thermal_zone_device->lock to avoid race condition. For example, during the system reboot, if the mali GPU device implements device shutdown callback and unregister GPU devfreq cooling device, the deleted list head may be accessed to cause panic, as the following log shows:

[   33.551070] c3 25 (kworker/3:0) Unable to handle kernel paging request at virtual address dead000000000070
[   33.566708] c3 25 (kworker/3:0) pgd = ffffffc0ed290000
[   33.572071] c3 25 (kworker/3:0) [dead000000000070] *pgd=00000001ed292003, *pud=00000001ed292003, *pmd=0000000000000000
[   33.581515] c3 25 (kworker/3:0) Internal error: Oops: 96000004 [#1] PREEMPT SMP
[   33.599761] c3 25 (kworker/3:0) CPU: 3 PID: 25 Comm: kworker/3:0 Not tainted 4.4.35+ #912
[   33.614137] c3 25 (kworker/3:0) Workqueue: events_freezable thermal_zone_device_check
[   33.620245] c3 25 (kworker/3:0) task: ffffffc0f32e4200 ti: ffffffc0f32f0000 task.ti: ffffffc0f32f0000
[   33.629466] c3 25 (kworker/3:0) PC is at power_allocator_throttle+0x7c8/0x8a4
[   33.636609] c3 25 (kworker/3:0) LR is at power_allocator_throttle+0x808/0x8a4
[   33.643742] c3 25 (kworker/3:0) pc : [<ffffff8008683dd0>] lr : [<ffffff8008683e10>] pstate: 20000145
[   33.652874] c3 25 (kworker/3:0) sp : ffffffc0f32f3bb0
[   34.468519] c3 25 (kworker/3:0) Process kworker/3:0 (pid: 25, stack limit = 0xffffffc0f32f0020)
[   34.477220] c3 25 (kworker/3:0) Stack: (0xffffffc0f32f3bb0 to 0xffffffc0f32f4000)
[   34.819822] c3 25 (kworker/3:0) Call trace:
[   34.824021] c3 25 (kworker/3:0) Exception stack(0xffffffc0f32f39c0 to 0xffffffc0f32f3af0)
[   34.924993] c3 25 (kworker/3:0) [<ffffff8008683dd0>] power_allocator_throttle+0x7c8/0x8a4
[   34.933184] c3 25 (kworker/3:0) [<ffffff80086807f4>] handle_thermal_trip.part.25+0x70/0x224
[   34.941545] c3 25 (kworker/3:0) [<ffffff8008680a68>] thermal_zone_device_update+0xc0/0x20c
[   34.949818] c3 25 (kworker/3:0) [<ffffff8008680bd4>] thermal_zone_device_check+0x20/0x2c
[   34.957924] c3 25 (kworker/3:0) [<ffffff80080b93a4>] process_one_work+0x168/0x458
[   34.965414] c3 25 (kworker/3:0) [<ffffff80080ba068>] worker_thread+0x13c/0x4b4
[   34.972650] c3 25 (kworker/3:0) [<ffffff80080c0a4c>] kthread+0xe8/0xfc
[   34.979187] c3 25 (kworker/3:0) [<ffffff8008084e90>] ret_from_fork+0x10/0x40
[   34.986244] c3 25 (kworker/3:0) Code: f9405e73 eb1302bf d102e273 54ffc460 (b9402a61)
[   34.994339] c3 25 (kworker/3:0) ---[ end trace 32057901e3b7e1db ]---

---
 drivers/thermal/power_allocator.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -523,6 +523,7 @@ static void allow_maximum_power(struct t
 	struct thermal_instance *instance;
 	struct power_allocator_params *params = tz->governor_data;
 
+	mutex_lock(&tz->lock);
 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 		if ((instance->trip != params->trip_max_desired_temperature) ||
 		    (!cdev_is_power_actor(instance->cdev)))

@@ -532,6 +533,7 @@ static void allow_maximum_power(struct t
 		instance->cdev->updated = false;
 		thermal_cdev_update(instance->cdev);
 	}
+	mutex_unlock(&tz->lock);
 }
 
 /**

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/thermal-power_allocator-fix-one-race-condition-issue-for-thermal_instances-list.patch