Alexander Duyck <alexander.h.du...@redhat.com> :
[...]
> In addition the r8169 uses a rmb() however I believe it is placed incorrectly
> as I assume it supposed to be ordering descriptor reads after the check for
> ownership.
Not exactly. It's a barrier against compiler optimization from 2004.
It should not matter.
However I disagree with the change below:
> @@ -7284,11 +7280,11 @@ static int rtl_rx(struct net_device *dev, struct
> rtl8169_private *tp, u32 budget
> struct RxDesc *desc = tp->RxDescArray + entry;
> u32 status;
>
> - rmb();
> - status = le32_to_cpu(desc->opts1) & tp->opts1_mask;
> -
> + status = cpu_to_le32(load_acquire(&desc->opts1));
> if (status & DescOwn)
> break;
> +
> + status &= tp->opts1_mask;
-> tp->opts1_mask is not __le32 tainted.
Btw, should I consider the sketch above as a skeleton in my r8169 closet ?
NIC CPU0 CPU1
| CPU | NIC | CPU | CPU |
| CPU | NIC | CPU | CPU |
^ tx_dirty
[start_xmit...
| CPU | CPU | CPU | CPU |
(NIC did it's job)
[rtl_tx...
| ... | ... | NIC | NIC |
(ring update)
(tx_dirty increases)
| CPU | CPU | ??? | ??? |
tx_dirty ?
reaping about-to-be-sent
buffers on some platforms ?
...start_xmit]
--
Ueimor
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