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Date: Fri, 23 Oct 2015 08:35:52 -0500 From: Tom Lendacky <thomas.lendacky@....com> To: David Miller <davem@...emloft.net> CC: <netdev@...r.kernel.org>, <christoffer.dall@...aro.org> Subject: Re: [PATCH net] amd-xgbe: Use wmb before updating current descriptor count On 10/23/2015 04:59 AM, David Miller wrote: > From: Tom Lendacky <thomas.lendacky@....com> > Date: Wed, 21 Oct 2015 15:37:05 -0500 > >> The code currently uses the lightweight dma_wmb barrier before updating >> the current descriptor count. Under heavy load, the Tx cleanup routine >> was seeing the updated current descriptor count before the updated >> descriptor information. As a result, the Tx descriptor was being cleaned >> up before it was used because it was not "owned" by the hardware yet, >> resulting in a Tx queue hang. >> >> Using the wmb barrier insures that the descriptor is updated before the >> descriptor counter preventing the Tx queue hang. For extra insurance, >> the Tx cleanup routine is changed to grab the current decriptor count on >> entry and uses that initial value in the processing loop rather than >> trying to chase the current value. >> >> Signed-off-by: Tom Lendacky <thomas.lendacky@....com> >> Tested-by: Christoffer Dall <christoffer.dall@...aro.org> > > Applied, thanks. Hi David, Can you queue this up for stable? It is applicable to 4.1 and 4.2. Thanks, Tom > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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