Re: [PATCH 1/2] ACPI / scan: Make acpi_bus_hot_remove_device() acquire the scan lock

[Toshi Kani <toshi.kani@hp.com>]

On Sat, 2013-02-09 at 15:29 +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> The ACPI scan lock has been introduced to prevent acpi_bus_scan()
> and acpi_bus_trim() from running in parallel with each other for
> overlapping ACPI namespace scopes.  However, it is not sufficient
> to do that, because if acpi_bus_scan() is run (for an overlapping
> namespace scope) right after the acpi_bus_trim() in
> acpi_bus_hot_remove_device(), the subsequent eject will remove
> devices without removing the corresponding struct acpi_device
> objects (and possibly companion "physical" device objects).
> Therefore acpi_bus_hot_remove_device() has to acquire the scan
> lock before carrying out the bus trimming and hold it through
> the evaluation of _EJ0, so make that happen.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Looks good.

Acked-by: Toshi Kani <toshi.kani@hp.com>

Thanks,
-Toshi


> ---
>  drivers/acpi/scan.c |   31 +++++++++++++++++--------------
>  1 file changed, 17 insertions(+), 14 deletions(-)
> 
> Index: test/drivers/acpi/scan.c
> ===================================================================
> --- test.orig/drivers/acpi/scan.c
> +++ test/drivers/acpi/scan.c
> @@ -95,6 +95,8 @@ acpi_device_modalias_show(struct device
>  }
>  static DEVICE_ATTR(modalias, 0444, acpi_device_modalias_show, NULL);
>  
> +static void __acpi_bus_trim(struct acpi_device *start);
> +
>  /**
>   * acpi_bus_hot_remove_device: hot-remove a device and its children
>   * @context: struct acpi_eject_event pointer (freed in this func)
> @@ -114,10 +116,12 @@ void acpi_bus_hot_remove_device(void *co
>  	acpi_status status = AE_OK;
>  	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
>  
> +	mutex_lock(&acpi_scan_lock);
> +
>  	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
>  		"Hot-removing device %s...\n", dev_name(&device->dev)));
>  
> -	acpi_bus_trim(device);
> +	__acpi_bus_trim(device);
>  	/* Device node has been released. */
>  	device = NULL;
>  
> @@ -146,18 +150,14 @@ void acpi_bus_hot_remove_device(void *co
>  	status = acpi_evaluate_object(handle, "_EJ0", &arg_list, NULL);
>  	if (ACPI_FAILURE(status)) {
>  		if (status != AE_NOT_FOUND)
> -			printk(KERN_WARNING PREFIX
> -					"Eject device failed\n");
> -		goto err_out;
> -	}
> +			acpi_handle_warn(handle, "Eject failed\n");
>  
> -	kfree(context);
> -	return;
> +		/* Tell the firmware the hot-remove operation has failed. */
> +		acpi_evaluate_hotplug_ost(handle, ej_event->event,
> +					  ost_code, NULL);
> +	}
>  
> -err_out:
> -	/* Inform firmware the hot-remove operation has completed w/ error */
> -	(void) acpi_evaluate_hotplug_ost(handle,
> -				ej_event->event, ost_code, NULL);
> +	mutex_unlock(&acpi_scan_lock);
>  	kfree(context);
>  	return;
>  }
> @@ -1686,10 +1686,8 @@ static acpi_status acpi_bus_remove(acpi_
>  	return AE_OK;
>  }
>  
> -void acpi_bus_trim(struct acpi_device *start)
> +static void __acpi_bus_trim(struct acpi_device *start)
>  {
> -	mutex_lock(&acpi_scan_lock);
> -
>  	/*
>  	 * Execute acpi_bus_device_detach() as a post-order callback to detach
>  	 * all ACPI drivers from the device nodes being removed.
> @@ -1704,7 +1702,12 @@ void acpi_bus_trim(struct acpi_device *s
>  	acpi_walk_namespace(ACPI_TYPE_ANY, start->handle, ACPI_UINT32_MAX, NULL,
>  			    acpi_bus_remove, NULL, NULL);
>  	acpi_bus_remove(start->handle, 0, NULL, NULL);
> +}
>  
> +void acpi_bus_trim(struct acpi_device *start)
> +{
> +	mutex_lock(&acpi_scan_lock);
> +	__acpi_bus_trim(start);
>  	mutex_unlock(&acpi_scan_lock);
>  }
>  EXPORT_SYMBOL_GPL(acpi_bus_trim);
>