netdev - RE: [RFC PATCH] bnx2x: fix tx queue locking and memory barriers

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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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