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Date:   Thu, 17 Sep 2020 16:57:41 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     olteanv@...il.com
Cc:     netdev@...r.kernel.org, yangbo.lu@....com,
        xiaoliang.yang_1@....com, UNGLinuxDriver@...rochip.com,
        claudiu.manoil@....com, alexandre.belloni@...tlin.com,
        andrew@...n.ch, vivien.didelot@...il.com, f.fainelli@...il.com,
        kuba@...nel.org
Subject: Re: [PATCH net 2/7] net: mscc: ocelot: add locking for the port TX
 timestamp ID

From: Vladimir Oltean <olteanv@...il.com>
Date: Fri, 18 Sep 2020 02:43:40 +0300

> On Wed, Sep 16, 2020 at 05:19:26PM -0700, David Miller wrote:
>> From: Vladimir Oltean <olteanv@...il.com>
>> Date: Tue, 15 Sep 2020 21:22:24 +0300
>>
>> > This is a problem because, at least theoretically, another timestampable
>> > skb might use the same ocelot_port->ts_id before that is incremented. So
>> > the logic of using and incrementing the timestamp id should be atomic
>> > per port.
>>
>> Have you actually observed this race in practice?
>>
>> All transmit calls are serialized by the netdev transmit spinlock.
>>
>> Let's not add locking if it is not actually necessary.
> 
> It's a bit more complicated.
> This code is also used from DSA, and DSA now declares NETIF_F_LLTX.

Please document that in the commit log message, thank you.

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