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SubjectRe: [PATCH net-next 5/9] sunvnet: add memory barrier before check for tx enable
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On Fri, 2017-02-03 at 09:42 -0800, Shannon Nelson wrote:
> In order to allow the underlying LDC and outstanding memory operations
> to potentially catch up with the driver's Tx requests, add a memory
> barrier before checking again for available tx descriptors.
>
> Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>
> ---
> drivers/net/ethernet/sun/sunvnet_common.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/net/ethernet/sun/sunvnet_common.c b/drivers/net/ethernet/sun/sunvnet_common.c
> index 5d0d386..98e758e 100644
> --- a/drivers/net/ethernet/sun/sunvnet_common.c
> +++ b/drivers/net/ethernet/sun/sunvnet_common.c
> @@ -1467,6 +1467,7 @@ ldc_start_done:
> dr->prod = (dr->prod + 1) & (VNET_TX_RING_SIZE - 1);
> if (unlikely(vnet_tx_dring_avail(dr) < 1)) {
> netif_tx_stop_queue(txq);
> + dma_wmb();

This does not look right.

I believe you need smp_rmb() here.

> if (vnet_tx_dring_avail(dr) > VNET_TX_WAKEUP_THRESH(dr))
> netif_tx_wake_queue(txq);
> }


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