On Fri, 2016-05-13 at 16:53 -0700, Iyappan Subramanian wrote:
> This patch fixes the race condition on updating the statistics
> counters by moving the counters to the ring structure.
>
...
> @@ -1127,12 +1127,31 @@ static struct rtnl_link_stats64
> *xgene_enet_get_stats64(
> {
> struct xgene_enet_pdata *pdata = netdev_priv(ndev);
> struct rtnl_link_stats64 *stats = &pdata->stats;
> + struct xgene_enet_desc_ring *ring;
> + int i;
> +
> + memset(stats, 0, sizeof(struct rtnl_link_stats64));
The memset() should already be done in the caller.
> + for (i = 0; i < pdata->txq_cnt; i++) {
> + ring = pdata->tx_ring[i];
> + if (ring) {
> + stats->tx_packets += ring->tx_packets;
> + stats->tx_bytes += ring->tx_bytes;
> + }
> + }
>
> - stats->rx_errors += stats->rx_length_errors +
> - stats->rx_crc_errors +
> - stats->rx_frame_errors +
> - stats->rx_fifo_errors;
Right, this piece was completely buggy.
Not a race, but rx_errors was growing every time stats were fetched on
this device.
stats->rx_errors = sum(...) was probably the intent.
> - memcpy(storage, &pdata->stats, sizeof(struct rtnl_link_stats64));
> + for (i = 0; i < pdata->rxq_cnt; i++) {
> + ring = pdata->rx_ring[i];
> + if (ring) {
> + stats->rx_packets += ring->rx_packets;
> + stats->rx_bytes += ring->rx_bytes;
> + stats->rx_errors += ring->rx_length_errors +
> + ring->rx_crc_errors +
> + ring->rx_frame_errors +
> + ring->rx_fifo_errors;
> + stats->rx_dropped += ring->rx_dropped;
> + }
> + }
> + memcpy(storage, stats, sizeof(struct rtnl_link_stats64));
>
> return storage;
> }
> diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.h
> b/drivers/net/ethernet/apm/xgene/xgene_enet_main.h
> index cc40c30..092fbec 100644
> --- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.h
> +++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.h
> @@ -121,6 +121,16 @@ struct xgene_enet_desc_ring {
> struct xgene_enet_raw_desc16 *raw_desc16;
> };
> __le64 *exp_bufs;
> + u64 tx_packets;
> + u64 tx_bytes;
> + u64 rx_packets;
> + u64 rx_bytes;
> + u64 rx_dropped;
> + u64 rx_errors;
> + u64 rx_length_errors;
> + u64 rx_crc_errors;
> + u64 rx_frame_errors;
> + u64 rx_fifo_errors;
Note that there is still a race on 32bit arches.
It seems this driver should really use "unsigned long" counters and
provide standard ndo_get_stats()
