netdev - Re: [PATCH net 2/7] net: mscc: ocelot: add locking for the port TX timestamp ID

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Message-Id: <20200916.171926.383551951466329210.davem@davemloft.net>
Date:   Wed, 16 Sep 2020 17:19:26 -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: 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.