[PATCH v2] Drivers: hv: vmbus: incorrect device name is printed when child device is unregistered

[PATCH v2] Drivers: hv: vmbus: incorrect device name is printed when child device is unregistered

[Fernando Soto]

From: Fernando Soto <fsoto@bluecatnetworks.com> 
Please CC me, I am not subscribed to the list.

Whenever a device is unregistered in vmbus_device_unregister (drivers/hv/vmbus_drv.c), the device name in the log message may contain garbage as the memory has already been freed by the time pr_info is called. Log example:
 [ 3149.170475] hv_vmbus: child device àõsèè0_5 unregistered

By logging the message just before calling device_unregister, the correct device name is printed:
[ 3145.034652] hv_vmbus: child device vmbus_0_5 unregistered

Also changing register & unregister messages to debug to avoid unnecessarily cluttering the kernel log.

Signed-off-by: Fernando M Soto <fsoto@bluecatnetworks.com>
--- linux-3.10-rc5/drivers/hv/vmbus_drv.c.orig	2013-06-13 19:20:55.359511352 -0400
+++ linux-3.10-rc5/drivers/hv/vmbus_drv.c	2013-06-14 19:00:21.722105728 -0400
@@ -686,7 +686,7 @@ int vmbus_device_register(struct hv_devi
 	if (ret)
 		pr_err("Unable to register child device\n");
 	else
-		pr_info("child device %s registered\n",
+		pr_debug("child device %s registered\n",
 			dev_name(&child_device_obj->device));
 
 	return ret;
@@ -698,14 +698,14 @@ int vmbus_device_register(struct hv_devi
  */
 void vmbus_device_unregister(struct hv_device *device_obj)
 {
+	pr_debug("child device %s unregistered\n",
+		dev_name(&device_obj->device));
+
 	/*
 	 * Kick off the process of unregistering the device.
 	 * This will call vmbus_remove() and eventually vmbus_device_release()
 	 */
 	device_unregister(&device_obj->device);
-
-	pr_info("child device %s unregistered\n",
-		dev_name(&device_obj->device));
 }
 
 
--

RE: [PATCH v2] Drivers: hv: vmbus: incorrect device name is printed when child device is unregistered

[KY Srinivasan]

> -----Original Message-----
> From: Fernando Soto [mailto:fsoto@bluecatnetworks.com]
> Sent: Friday, June 14, 2013 7:14 PM
> To: linux-kernel@vger.kernel.org
> Cc: Haiyang Zhang; KY Srinivasan; Greg KH (gregkh@linuxfoundation.org)
> Subject: [PATCH v2] Drivers: hv: vmbus: incorrect device name is printed when
> child device is unregistered
> 
> From: Fernando Soto <fsoto@bluecatnetworks.com>
> Please CC me, I am not subscribed to the list.
> 
> Whenever a device is unregistered in vmbus_device_unregister
> (drivers/hv/vmbus_drv.c), the device name in the log message may contain
> garbage as the memory has already been freed by the time pr_info is called. Log
> example:
>  [ 3149.170475] hv_vmbus: child device àõsèè0_5 unregistered
> 
> By logging the message just before calling device_unregister, the correct device
> name is printed:
> [ 3145.034652] hv_vmbus: child device vmbus_0_5 unregistered
> 
> Also changing register & unregister messages to debug to avoid unnecessarily
> cluttering the kernel log.
> 
> Signed-off-by: Fernando M Soto <fsoto@bluecatnetworks.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> --- linux-3.10-rc5/drivers/hv/vmbus_drv.c.orig	2013-06-13 19:20:55.359511352 -
> 0400
> +++ linux-3.10-rc5/drivers/hv/vmbus_drv.c	2013-06-14 19:00:21.722105728 -
> 0400
> @@ -686,7 +686,7 @@ int vmbus_device_register(struct hv_devi
>  	if (ret)
>  		pr_err("Unable to register child device\n");
>  	else
> -		pr_info("child device %s registered\n",
> +		pr_debug("child device %s registered\n",
>  			dev_name(&child_device_obj->device));
> 
>  	return ret;
> @@ -698,14 +698,14 @@ int vmbus_device_register(struct hv_devi
>   */
>  void vmbus_device_unregister(struct hv_device *device_obj)
>  {
> +	pr_debug("child device %s unregistered\n",
> +		dev_name(&device_obj->device));
> +
>  	/*
>  	 * Kick off the process of unregistering the device.
>  	 * This will call vmbus_remove() and eventually vmbus_device_release()
>  	 */
>  	device_unregister(&device_obj->device);
> -
> -	pr_info("child device %s unregistered\n",
> -		dev_name(&device_obj->device));
>  }
> 
> 
> --
>