netdev - Re: [PATCH] 3c59x: fix missing dma_mapping

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Message-Id: <20180103.095324.2019351026018947051.davem@davemloft.net>
Date:   Wed, 03 Jan 2018 09:53:24 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     nhorman@...driver.com
Cc:     netdev@...r.kernel.org, nhorman@...hat.com,
        klassert@...hematik.tu-chemnitz.de
Subject: Re: [PATCH] 3c59x: fix missing dma_mapping_error check

From: Neil Horman <nhorman@...driver.com>
Date: Wed, 3 Jan 2018 05:42:04 -0500

> On Tue, Jan 02, 2018 at 09:48:27PM -0500, David Miller wrote:
>> And for the RX cases, it allows the RX ring to deplete to empty which
>> tends to hang most chips.  You need to make the DMA failure detection
>> early and recycle the RX buffer back to the chip instead of passing
>> it up to the stack.
>> 
> Strictly speaking, I think we're ok here, because the dirty_rx counter creates a
> contiguous area to refill, and we will just pick up where we left off on the
> next napi poll.

If you continually fail the mappings, even NAPI poll, eventually the
RX ring will empty.

I don't think we're ok here.