netdev - Re: [net-2.6 PATCH 2/6] net: remove kfree_skb on a NULL pointer in af

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Date:	Mon, 21 Sep 2009 12:04:35 +0000
From:	John Fastabend <john.r.fastabend@...el.com>
To:	David Miller <davem@...emloft.net>
CC:	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: Re: [net-2.6 PATCH 2/6] net: remove kfree_skb on a NULL pointer in
 af_netlink.c

David Miller wrote:
> From: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> Date: Thu, 17 Sep 2009 17:57:29 -0700
>
>   
>> From: John Fastabend <john.r.fastabend@...el.com>
>>
>> This removes a kfree_skb that is being called on a NULL pointer when
>> do_one_broadcast() is sucessful.  And moves the kfree_skb into
>> do_one_broadcast() for the error case.
>>
>> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
>> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
>>     
>
> kfree_skb() on a NULL pointer is completely legal.
>   
OK, but this depends on the unlikely() macro in kfree_skb() to catch a 
case that is the expected non-error case. Would it be better to wrap the 
kfree_skb() in an if statement to avoid hitting the unlikely() macro?  
Or is the performance hit from the unlikely() macro so small this is not 
an issue?  Thanks for looking at these.

john.

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