On Wednesday, September 12, 2012, Aaron Lu wrote:
> Commit 0090def("ACPI: Add interface to register/unregister device
> to/from power resources") used resource_lock to protect the devices list
> that relies on power resource. It caused a mutex dead lock, as below
>
> acpi_power_on ---> lock resource_lock
> __acpi_power_on
> acpi_power_on_device
> acpi_power_get_inferred_state
> acpi_power_get_list_state ---> lock resource_lock
>
> This patch adds a new mutex "devices_lock" to protect the devices list
> and calls acpi_power_on_device in acpi_power_on, instead of
> __acpi_power_on, after the resource_lock is released.
>
> Signed-off-by: Lin Ming <ming.m.lin@xxxxxxxxx>
> Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
Good catch, thanks.
I hope Len won't mind if I take it for v3.6.
> ---
> v2:
> If power resource is already on, no need to check if device needs
> to be resumed.
> v1:
> By Lin Ming.
>
> drivers/acpi/power.c | 36 ++++++++++++++++++++++++------------
> 1 file changed, 24 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
> index 215ecd0..3582a26 100644
> --- a/drivers/acpi/power.c
> +++ b/drivers/acpi/power.c
> @@ -105,6 +105,7 @@ struct acpi_power_resource {
>
> /* List of devices relying on this power resource */
> struct acpi_power_resource_device *devices;
> + struct mutex devices_lock;
> };
>
> static struct list_head acpi_power_resource_list;
> @@ -223,7 +224,6 @@ static void acpi_power_on_device(struct acpi_power_managed_device *device)
>
> static int __acpi_power_on(struct acpi_power_resource *resource)
> {
> - struct acpi_power_resource_device *device_list = resource->devices;
> acpi_status status = AE_OK;
>
> status = acpi_evaluate_object(resource->device->handle, "_ON", NULL, NULL);
> @@ -236,19 +236,14 @@ static int __acpi_power_on(struct acpi_power_resource *resource)
> ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Power resource [%s] turned on\n",
> resource->name));
>
> - while (device_list) {
> - acpi_power_on_device(device_list->device);
> -
> - device_list = device_list->next;
> - }
> -
> return 0;
> }
>
> static int acpi_power_on(acpi_handle handle)
> {
> - int result = 0;
> + int result = 0, resume_device = 0;
I'll change the data type of resume_device to bool when applying the patch.
> struct acpi_power_resource *resource = NULL;
> + struct acpi_power_resource_device *device_list;
>
> result = acpi_power_get_context(handle, &resource);
> if (result)
> @@ -264,10 +259,26 @@ static int acpi_power_on(acpi_handle handle)
> result = __acpi_power_on(resource);
> if (result)
> resource->ref_count--;
> + else
> + resume_device = 1;
> }
>
> mutex_unlock(&resource->resource_lock);
>
> + if (!resume_device)
> + return result;
> +
> + mutex_lock(&resource->devices_lock);
> +
> + device_list = resource->devices;
> + while (device_list) {
> + acpi_power_on_device(device_list->device);
> +
> + device_list = device_list->next;
> + }
> +
> + mutex_unlock(&resource->devices_lock);
> +
> return result;
> }
>
> @@ -353,7 +364,7 @@ static void __acpi_power_resource_unregister_device(struct device *dev,
> if (acpi_power_get_context(res_handle, &resource))
> return;
>
> - mutex_lock(&resource->resource_lock);
> + mutex_lock(&resource->devices_lock);
> prev = NULL;
> curr = resource->devices;
> while (curr) {
> @@ -370,7 +381,7 @@ static void __acpi_power_resource_unregister_device(struct device *dev,
> prev = curr;
> curr = curr->next;
> }
> - mutex_unlock(&resource->resource_lock);
> + mutex_unlock(&resource->devices_lock);
> }
>
> /* Unlink dev from all power resources in _PR0 */
> @@ -412,10 +423,10 @@ static int __acpi_power_resource_register_device(
>
> power_resource_device->device = powered_device;
>
> - mutex_lock(&resource->resource_lock);
> + mutex_lock(&resource->devices_lock);
> power_resource_device->next = resource->devices;
> resource->devices = power_resource_device;
> - mutex_unlock(&resource->resource_lock);
> + mutex_unlock(&resource->devices_lock);
>
> return 0;
> }
> @@ -719,6 +730,7 @@ static int acpi_power_add(struct acpi_device *device)
>
> resource->device = device;
> mutex_init(&resource->resource_lock);
> + mutex_init(&resource->devices_lock);
> strcpy(resource->name, device->pnp.bus_id);
> strcpy(acpi_device_name(device), ACPI_POWER_DEVICE_NAME);
> strcpy(acpi_device_class(device), ACPI_POWER_CLASS);
>
Thanks,
Rafael
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