netdev - Re: [net-next PATCH v4 02/10] net: Add queue and napi association

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Message-ID: <ae9616c7-fd96-4d38-9598-89b9082baadf@intel.com>
Date: Wed, 11 Oct 2023 16:36:48 -0700
From: "Nambiar, Amritha" <amritha.nambiar@...el.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: <netdev@...r.kernel.org>, <sridhar.samudrala@...el.com>
Subject: Re: [net-next PATCH v4 02/10] net: Add queue and napi association

On 10/10/2023 7:17 PM, Jakub Kicinski wrote:
> On Fri, 06 Oct 2023 02:14:48 -0700 Amritha Nambiar wrote:
>>   #endif
>> +	/* NAPI instance for the queue */
>> +	struct napi_struct		*napi;
> 
> What's the protection on this field?
> Writers and readers must be under rtnl_lock?
> 

Yes, writers and readers must be under rtnl_lock. I will modify 
netif_queue_set_napi() for rtnl protection from writers. Readers are 
holding rtnl_lock.

>>   } ____cacheline_aligned_in_smp;
>>   
>>   /*
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 606a366cc209..9b63a7b76c01 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -6394,6 +6394,40 @@ int dev_set_threaded(struct net_device *dev, bool threaded)
>>   }
>>   EXPORT_SYMBOL(dev_set_threaded);
>>   
>> +/**
>> + * netif_queue_set_napi - Associate queue with the napi
>> + * @queue_index: Index of queue
>> + * @type: queue type as RX or TX
>> + * @napi: NAPI context
>> + *
>> + * Set queue with its corresponding napi context
> 
> Let's add more relevant info, like the fact that NAPI must already be
> added before calling, calling context, etc.
> 

Okay, will fix in v5.

>> + */
>> +int netif_queue_set_napi(unsigned int queue_index, enum netdev_queue_type type,
>> +			 struct napi_struct *napi)
> 
> Let's make this helper void.
> It will be a PITA for callers to handle any error this may return.
> 

Okay, will make this a void function in v5.

>> +{
>> +	struct net_device *dev = napi->dev;
>> +	struct netdev_rx_queue *rxq;
>> +	struct netdev_queue *txq;
>> +
>> +	if (!dev)
>> +		return -EINVAL;
> 
> 	if (WARN_ON_ONCE(...))
> 		return;
> 
>> +	default:
>> +		return -EINVAL;
>> +	}
> 
> same here

Will fix in v5.