netdev - Re: [PATCH][net-next] openvswitch: change the data type of error status to atomic_long

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Message-ID: <CAJFZqHzeCCRJgrx5dTuLBMtfNf4QKkxU77PJXNXWuYcoBFuZWw@mail.gmail.com>
Date:	Mon, 8 Sep 2014 19:23:11 +0800
From:	Li RongQing <roy.qing.li@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	Pravin Shelar <pshelar@...ira.com>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH][net-next] openvswitch: change the data type of error
 status to atomic_long_t

On Mon, Sep 8, 2014 at 7:17 AM, David Miller <davem@...emloft.net> wrote:
> From: Li RongQing <roy.qing.li@...il.com>
> Date: Sun, 7 Sep 2014 17:24:11 +0800
>
>> 2.  I did not find that tx_dropped/tx_error/.. is protected by spin
>> lock under net dir,
>> sometime tx_dropped is atomic_long_t; sometime it is percpu variable;
>> sometime it is
>> u64,but does not need to protect.
>
> If it is only modified in ->ndo_start_xmit() then it is protected by
> the per-queue TX lock, as ->ndo_start_xmit() is always invoked with
> it held (except in LLTX drivers of course).


But reading tx_dropped is in process context, and maybe break by interrupt or
soft interrupt,  and no lock protect, or not the same lock protect.

-Roy
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