Re: [PATCH 2/3] ACPI: Get acpi_device's parent from the parent field

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Wed, Nov 03, 2021 at 03:34:05PM +0200, Sakari Ailus wrote:
> Printk modifier %pfw is used to print the full path of the device name.
> This is obtained device by device until a device no longer has a parent.
> 
> On ACPI getting the parent fwnode is done by calling acpi_get_parent()
> which tries to down() a semaphore. But local IRQs are now disabled in
> vprintk_store() before the mutex is acquired. This is obviously a problem.
> 
> Luckily struct acpi_device has a parent field already. Use that field to
> get the parent instead of relying on acpi_get_parent().

I think the best if Rafael can confirm that we may use it like this.
If he approved, nothing would stop me to give you
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>

> Fixes: 002eb6ad0751 ("printk: track/limit recursion")
> Cc: stable@vger.kernel.org # v5.15 and up
> Depends-on: ("ACPI: Make acpi_fwnode_handle safer")
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
>  drivers/acpi/property.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
> index e312ebaed8db4..7403ee2816eb8 100644
> --- a/drivers/acpi/property.c
> +++ b/drivers/acpi/property.c
> @@ -1089,16 +1089,12 @@ struct fwnode_handle *acpi_node_get_parent(const struct fwnode_handle *fwnode)
>  	if (is_acpi_data_node(fwnode)) {
>  		/* All data nodes have parent pointer so just return that */
>  		return to_acpi_data_node(fwnode)->parent;
> -	} else if (is_acpi_device_node(fwnode)) {
> -		acpi_handle handle, parent_handle;
> +	}
>  
> -		handle = to_acpi_device_node(fwnode)->handle;
> -		if (ACPI_SUCCESS(acpi_get_parent(handle, &parent_handle))) {
> -			struct acpi_device *adev;
> +	if (is_acpi_device_node(fwnode)) {
> +		struct acpi_device *device = to_acpi_device_node(fwnode);
>  
> -			if (!acpi_bus_get_device(parent_handle, &adev))
> -				return acpi_fwnode_handle(adev);
> -		}
> +		return acpi_fwnode_handle(device->parent);
>  	}
>  
>  	return NULL;
> -- 
> 2.30.2
> 
> 

-- 
With Best Regards,
Andy Shevchenko