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

Andy Shevchenko
2021-11-03T17:04:10Z

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