Re: [PATCH] thermal: power_allocator: fix one race condition issue for thermal_instances list

[Zhang Rui <rui.zhang@intel.com>]

On Tue, 2017-12-26 at 19:22 +0800, Yi Zeng wrote:
> 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 ]-
> --
> 
> Signed-off-by: Yi Zeng <yizeng@asrmicro.com>

applied.

thanks,
rui
> ---
>  drivers/thermal/power_allocator.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/thermal/power_allocator.c
> b/drivers/thermal/power_allocator.c
> index b4d3116..3055f9a 100644
> --- a/drivers/thermal/power_allocator.c
> +++ b/drivers/thermal/power_allocator.c
> @@ -523,6 +523,7 @@ static void allow_maximum_power(struct
> thermal_zone_device *tz)
>  	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)))
> @@ -534,6 +535,7 @@ static void allow_maximum_power(struct
> thermal_zone_device *tz)
>  		mutex_unlock(&instance->cdev->lock);
>  		thermal_cdev_update(instance->cdev);
>  	}
> +	mutex_unlock(&tz->lock);
>  }
>  
>  /**