Re: [2.6.5] Bad scheduling while atomic

Re: [2.6.5] Bad scheduling while atomic

[Stephen Hemminger]

Bring up/down network devices with lapbether causes scheduling while
atomic (if preempt enabled).

The calls to rcu_read_lock are unnecessary since lapb_device_event 
is called from notifier with the rtnetlink semaphore held, it is
already protected from the labp_devices list changing.

Patch against 2.6.6-rc1

diff -Nru a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c
--- a/drivers/net/wan/lapbether.c	Fri Apr 16 11:00:35 2004
+++ b/drivers/net/wan/lapbether.c	Fri Apr 16 11:00:35 2004
@@ -392,6 +392,8 @@
 
 /*
  *	Handle device status changes.
+ *
+ * Called from notifier with RTNL held.
  */
 static int lapbeth_device_event(struct notifier_block *this,
 				unsigned long event, void *ptr)
@@ -402,7 +404,6 @@
 	if (!dev_is_ethdev(dev))
 		return NOTIFY_DONE;
 
-	rcu_read_lock();
 	switch (event) {
 	case NETDEV_UP:
 		/* New ethernet device -> new LAPB interface	 */
@@ -422,7 +423,6 @@
 			lapbeth_free_device(lapbeth);
 		break;
 	}
-	rcu_read_unlock();
 
 	return NOTIFY_DONE;
 }

Re: [2.6.5] Bad scheduling while atomic

[David S. Miller]

On Fri, 16 Apr 2004 13:16:33 -0700
Stephen Hemminger <shemminger@osdl.org> wrote:

> Bring up/down network devices with lapbether causes scheduling while
> atomic (if preempt enabled).
> 
> The calls to rcu_read_lock are unnecessary since lapb_device_event 
> is called from notifier with the rtnetlink semaphore held, it is
> already protected from the labp_devices list changing.

Applied, thanks Stephen.

RE: [2.6.5] Bad scheduling while atomic

[Paul Rolland]

Thanks Stephen for being so fast !

Regards,
Paul

Paul Rolland, rol(at)as2917.net
ex-AS2917 Network administrator and Peering Coordinator

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> -----Message d'origine-----
> De : linux-kernel-owner@vger.kernel.org 
> [mailto:linux-kernel-owner@vger.kernel.org] De la part de 
> Stephen Hemminger
> Envoyé : vendredi 16 avril 2004 22:17
> À : David S. Miller
> Cc : Paul Rolland; linux-kernel@vger.kernel.org; netdev@oss.sgi.com
> Objet : Re: [2.6.5] Bad scheduling while atomic
> 
> Bring up/down network devices with lapbether causes scheduling while
> atomic (if preempt enabled).
> 
> The calls to rcu_read_lock are unnecessary since lapb_device_event 
> is called from notifier with the rtnetlink semaphore held, it is
> already protected from the labp_devices list changing.
> 
> Patch against 2.6.6-rc1
> 
> diff -Nru a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c
> --- a/drivers/net/wan/lapbether.c	Fri Apr 16 11:00:35 2004
> +++ b/drivers/net/wan/lapbether.c	Fri Apr 16 11:00:35 2004
> @@ -392,6 +392,8 @@
>  
>  /*
>   *	Handle device status changes.
> + *
> + * Called from notifier with RTNL held.
>   */
>  static int lapbeth_device_event(struct notifier_block *this,
>  				unsigned long event, void *ptr)
> @@ -402,7 +404,6 @@
>  	if (!dev_is_ethdev(dev))
>  		return NOTIFY_DONE;
>  
> -	rcu_read_lock();
>  	switch (event) {
>  	case NETDEV_UP:
>  		/* New ethernet device -> new LAPB interface	 */
> @@ -422,7 +423,6 @@
>  			lapbeth_free_device(lapbeth);
>  		break;
>  	}
> -	rcu_read_unlock();
>  
>  	return NOTIFY_DONE;
>  }
> -
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