netdev - Re: [PATCH net] net: lapbether: Prevent racing when checking whether the netif is running

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Message-ID: <CAJht_EMR6kqsetwNUbJJziLW97T0pXBSqSNZ5ma-q175cxoKyQ@mail.gmail.com>
Date:   Thu, 11 Mar 2021 15:13:01 -0800
From:   Xie He <xie.he.0141@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Martin Schiller <ms@....tdt.de>,
        "David S. Miller" <davem@...emloft.net>,
        Linux X25 <linux-x25@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: lapbether: Prevent racing when checking whether
 the netif is running

On Thu, Mar 11, 2021 at 2:52 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> Normally driver's ndo_stop() calls netif_tx_disable() which takes TX
> locks, so unless your driver is lockless (LLTX) there should be no xmit
> calls after that point.

Do you mean I should call "netif_tx_disable" inside my "ndo_stop"
function as a fix for the racing between "ndo_stop" and
"ndo_start_xmit"?

I can't call "netif_tx_disable" inside my "ndo_stop" function because
"netif_tx_disable" will call "netif_tx_stop_queue", which causes
another racing problem. Please see my recent commit f7d9d4854519
("net: lapbether: Remove netif_start_queue / netif_stop_queue")