netdev - Re: [PATCH (net.git) 5/6] stmmac: remove useless check in the stmmac_tx

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Message-ID: <530F0C65.4080905@st.com>
Date:	Thu, 27 Feb 2014 10:59:01 +0100
From:	Giuseppe CAVALLARO <peppe.cavallaro@...com>
To:	David Miller <davem@...emloft.net>
Cc:	<netdev@...r.kernel.org>
Subject: Re: [PATCH (net.git) 5/6] stmmac: remove useless check in the stmmac_tx_clean

On 2/26/2014 10:14 PM, David Miller wrote:
> From: Giuseppe Cavallaro <peppe.cavallaro@...com>
> Date: Wed, 26 Feb 2014 09:01:06 +0100
>
>> There is an useless if condition that this patch is removing
>> when the driver cleans the tx resources.
>>
>> Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@...com>
>
> It is not useless, the first check is optimistic and lock free.
>
> You must retest the condition under the lock in order to avoid
> spurious wakeups.
>
> Such a spurious wakeup could overlap another asynchronous context
> filling the TX queue and sleeping it, resulting in corruption.
>
> Furthermore, that cleanup patch in this series is absolutely not
> appropriate for 'net' which is for real bug fixes only.  Specifically
> I'm talking about patch #4.
>
>

Ok  I will send the patches w/o the #4. Thx for your advice

peppe
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