netdev - Re: [PATCH v3 6/6] net: sh

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Message-id: <4FB30D79.7060101@renesas.com>
Date:	Wed, 16 May 2012 11:14:17 +0900
From:	"Shimoda, Yoshihiro" <yoshihiro.shimoda.uh@...esas.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, linux-sh@...r.kernel.org
Subject: Re: [PATCH v3 6/6] net: sh_eth: use NAPI

2012/05/16 2:05, David Miller wrote:
> From: "Shimoda, Yoshihiro" <yoshihiro.shimoda.uh@...esas.com>
> Date: Tue, 15 May 2012 18:46:25 +0900
> 
>> 2012/05/15 14:07, David Miller wrote:
>>> From: "Shimoda, Yoshihiro" <yoshihiro.shimoda.uh@...esas.com>
>>> Date: Tue, 15 May 2012 13:47:44 +0900
>>>
>>>> 2012/05/15 7:50, David Miller wrote:
>>>>> You need strict synchronization between your TX queueing and TX
>>>>> liberation flows.  So that queue stop and wake are only performed
>>>>> at the correct moment.
>>>>
>>>> I will add netif_queue_stopped() in the sh_eth_poll().
>>>
>>> That doesn't fix the bug.  What if someone transmits a packet and
>>> fills the TX queue between the netif_queue_stopped() test and the
>>> call to netif_wake_queue()?
>>>
>>> Adding another test doesn't create the necessary synchronization.
>>>
>>
>> Thank you for the reply again.
>> I will modify the code as the following. Is it correct?
>>
>> 	if (txfree_num) {
>> 		netif_tx_lock(ndev);
>> 		if (netif_queue_stopped(ndev))
>> 			netif_wake_queue(ndev);
>> 		netif_tx_unlock(ndev);
>> 	}
> 
> Yes, and then you don't need that private lock in the start_xmit()
> method at all, since that method runs with the tx_lock held.
> 

Thank you for the reply. I will also modify the start_xmit().

Best regards,
Yoshihiro Shimoda
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