netdev - Re: [PATCH] net: renesas: sh_eth: Fix freeing wrong tx descriptor

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Date:   Tue, 7 Sep 2021 22:29:56 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        <davem@...emloft.net>, <kuba@...nel.org>
CC:     <netdev@...r.kernel.org>, <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH] net: renesas: sh_eth: Fix freeing wrong tx descriptor

On 9/7/21 2:29 PM, Yoshihiro Shimoda wrote:

> The cur_tx counter must be incremented after TACT bit of
> txdesc->status was set. However, a CPU is possible to reorder
> instructions and/or memory accesses between cur_tx and
> txdesc->status. And then, if TX interrupt happened at such a
> timing, the sh_eth_tx_free() may free the descriptor wrongly.
> So, add wmb() before cur_tx++.

   Not dma_wmb()? :-)

> Otherwise NETDEV WATCHDOG timeout is possible to happen.
> 
> Fixes: 86a74ff21a7a ("net: sh_eth: add support for Renesas SuperH Ethernet")
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>

Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>

[...]

MBR, Sergey