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Message-ID: <8628FE4E7912BF47A96AE7DD7BAC0AADCB46A2ADD1@SJEXCHCCR02.corp.ad.broadcom.com>
Date: Thu, 25 Feb 2010 08:14:58 -0800
From: "Vladislav Zolotarov" <vladz@...adcom.com>
To: "Stanislaw Gruszka" <sgruszka@...hat.com>
cc: "David Miller" <davem@...emloft.net>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"Eilon Greenstein" <eilong@...adcom.com>,
"dhowells@...hat.com" <dhowells@...hat.com>
Subject: RE: [RFC PATCH] bnx2x: fix tx queue locking and memory barriers
Correct. There a missing barrier in bnx2x_tx_int(). I'll create a proper patch shortly.
Thanks.
> -----Original Message-----
> From: Stanislaw Gruszka [mailto:sgruszka@...hat.com]
> Sent: Thursday, February 25, 2010 6:03 PM
> To: Vladislav Zolotarov
> Cc: David Miller; netdev@...r.kernel.org; Eilon Greenstein;
> dhowells@...hat.com
> Subject: Re: [RFC PATCH] bnx2x: fix tx queue locking and
> memory barriers
>
> On Thu, 25 Feb 2010 07:49:48 -0800
> "Vladislav Zolotarov" <vladz@...adcom.com> wrote:
>
> > In bnx2x_start_xmit(): right after the "stop queue" there
> is an smp_mb(), which will bring the cpu0 cache and a fresh
> fp->tx_bd_cons value to cpu1 and the following if() will
> return true and the queue will be released from
> bnx2x_start_xmit() flow.
>
> If I understand correctly what is written in
> Documentation/memory-barriers.txt
> this smp_mb() need to have another "paired" smp_{w}mb() on
> cpu0 to make value
> be updated on cpu1, which is missing.
>
>
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