[PATCH net-2.6.24] e100: fix driver init lockup on e100_up()

[PATCH net-2.6.24] e100: fix driver init lockup on e100_up()

[James Chapman]

Recent NAPI changes require that napi_enable() is always matched with
a napi_disable(). This patch makes sure that this invariant holds for
e100. It also moves the netif_napi_add() call until after private
pointers have been intialized, though this might only be significant
for cases where netpoll is being used.

Signed-off-by: James Chapman <jchapman@katalix.com>

diff --git a/drivers/net/e100.c b/drivers/net/e100.c
index e25f5ec..48996a4 100644
--- a/drivers/net/e100.c
+++ b/drivers/net/e100.c
@@ -2575,11 +2575,12 @@ static int __devinit e100_probe(struct pci_dev *pdev,
 	strncpy(netdev->name, pci_name(pdev), sizeof(netdev->name) - 1);
 
 	nic = netdev_priv(netdev);
-	netif_napi_add(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);
 	nic->netdev = netdev;
 	nic->pdev = pdev;
 	nic->msg_enable = (1 << debug) - 1;
 	pci_set_drvdata(pdev, netdev);
+	netif_napi_add(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);
+	napi_disable(&nic->napi);
 
 	if((err = pci_enable_device(pdev))) {
 		DPRINTK(PROBE, ERR, "Cannot enable PCI device, aborting.\n");

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Re: [E1000-devel] [PATCH net-2.6.24] e100: fix driver init lockup on e100_up()

[Kok, Auke]

James Chapman wrote:
> Recent NAPI changes require that napi_enable() is always matched with
> a napi_disable(). This patch makes sure that this invariant holds for
> e100. It also moves the netif_napi_add() call until after private
> pointers have been intialized, though this might only be significant
> for cases where netpoll is being used.
> 
> Signed-off-by: James Chapman <jchapman@katalix.com>
> 
> diff --git a/drivers/net/e100.c b/drivers/net/e100.c
> index e25f5ec..48996a4 100644
> --- a/drivers/net/e100.c
> +++ b/drivers/net/e100.c
> @@ -2575,11 +2575,12 @@ static int __devinit e100_probe(struct pci_dev *pdev,
>  	strncpy(netdev->name, pci_name(pdev), sizeof(netdev->name) - 1);
>  
>  	nic = netdev_priv(netdev);
> -	netif_napi_add(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);
>  	nic->netdev = netdev;
>  	nic->pdev = pdev;
>  	nic->msg_enable = (1 << debug) - 1;
>  	pci_set_drvdata(pdev, netdev);
> +	netif_napi_add(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);
> +	napi_disable(&nic->napi);

Just wondering, could we even reverse this order? IOW disable NAPI first, then 
add it ?

Otherwise this sounds OK to me.

Auke

Re: [E1000-devel] [PATCH net-2.6.24] e100: fix driver init lockup on e100_up()

[James Chapman]

Kok, Auke wrote:
> James Chapman wrote:
>> Recent NAPI changes require that napi_enable() is always matched with
>> a napi_disable(). This patch makes sure that this invariant holds for
>> e100. It also moves the netif_napi_add() call until after private
>> pointers have been intialized, though this might only be significant
>> for cases where netpoll is being used.
>>
>> Signed-off-by: James Chapman <jchapman@katalix.com>
>>
>> diff --git a/drivers/net/e100.c b/drivers/net/e100.c
>> index e25f5ec..48996a4 100644
>> --- a/drivers/net/e100.c
>> +++ b/drivers/net/e100.c
>> @@ -2575,11 +2575,12 @@ static int __devinit e100_probe(struct pci_dev 
>> *pdev,
>>      strncpy(netdev->name, pci_name(pdev), sizeof(netdev->name) - 1);
>>  
>>      nic = netdev_priv(netdev);
>> -    netif_napi_add(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);
>>      nic->netdev = netdev;
>>      nic->pdev = pdev;
>>      nic->msg_enable = (1 << debug) - 1;
>>      pci_set_drvdata(pdev, netdev);
>> +    netif_napi_add(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);
>> +    napi_disable(&nic->napi);
> 
> Just wondering, could we even reverse this order? IOW disable NAPI 
> first, then add it ?

I think the order shouldn't matter. DaveM?

> Otherwise this sounds OK to me.

-- 
James Chapman
Katalix Systems Ltd
http://www.katalix.com
Catalysts for your Embedded Linux software development

Re: [E1000-devel] [PATCH net-2.6.24] e100: fix driver init lockup on e100_up()

[David Miller]

From: James Chapman <jchapman@katalix.com>
Date: Mon, 27 Aug 2007 22:03:15 +0100

> Kok, Auke wrote:
> > James Chapman wrote:
> >>      nic = netdev_priv(netdev);
> >> -    netif_napi_add(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);
> >>      nic->netdev = netdev;
> >>      nic->pdev = pdev;
> >>      nic->msg_enable = (1 << debug) - 1;
> >>      pci_set_drvdata(pdev, netdev);
> >> +    netif_napi_add(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);
> >> +    napi_disable(&nic->napi);
> > 
> > Just wondering, could we even reverse this order? IOW disable NAPI 
> > first, then add it ?
> 
> I think the order shouldn't matter. DaveM?

It doesn't matter.

I'm beginning to think maybe we should do an implicit napi_disable()
in netif_napi_add(), then it's easier for drivers to play nice.

On open you do napi_enable(), in close you do napi_disable().
That's it.

And anywhere else in your driver that you have to napi_disable()
(suspend, recovering from hardware errors, etc.) you must be sure to
do the associated napi_enable() later on in order to keep things
balanced.