| Message ID | 20231220234739.13753-1-davthompson@nvidia.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | dcea1bd45e6d111cc8fc1aaefa7e31694089bda3 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v2] mlxbf_gige: fix receive packet race condition | expand |
Hello: This patch was applied to netdev/net.git (main) by David S. Miller <davem@davemloft.net>: On Wed, 20 Dec 2023 18:47:39 -0500 you wrote: > Under heavy traffic, the BlueField Gigabit interface can > become unresponsive. This is due to a possible race condition > in the mlxbf_gige_rx_packet function, where the function exits > with producer and consumer indices equal but there are remaining > packet(s) to be processed. In order to prevent this situation, > read receive consumer index *before* the HW replenish so that > the mlxbf_gige_rx_packet function returns an accurate return > value even if a packet is received into just-replenished buffer > prior to exiting this routine. If the just-replenished buffer > is received and occupies the last RX ring entry, the interface > would not recover and instead would encounter RX packet drops > related to internal buffer shortages since the driver RX logic > is not being triggered to drain the RX ring. This patch will > address and prevent this "ring full" condition. > > [...] Here is the summary with links: - [net,v2] mlxbf_gige: fix receive packet race condition https://git.kernel.org/netdev/net/c/dcea1bd45e6d You are awesome, thank you!
diff --git a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c index 0d5a41a2ae01..227d01cace3f 100644 --- a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c +++ b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c @@ -267,6 +267,13 @@ static bool mlxbf_gige_rx_packet(struct mlxbf_gige *priv, int *rx_pkts) priv->stats.rx_truncate_errors++; } + /* Read receive consumer index before replenish so that this routine + * returns accurate return value even if packet is received into + * just-replenished buffer prior to exiting this routine. + */ + rx_ci = readq(priv->base + MLXBF_GIGE_RX_CQE_PACKET_CI); + rx_ci_rem = rx_ci % priv->rx_q_entries; + /* Let hardware know we've replenished one buffer */ rx_pi++; @@ -279,8 +286,6 @@ static bool mlxbf_gige_rx_packet(struct mlxbf_gige *priv, int *rx_pkts) rx_pi_rem = rx_pi % priv->rx_q_entries; if (rx_pi_rem == 0) priv->valid_polarity ^= 1; - rx_ci = readq(priv->base + MLXBF_GIGE_RX_CQE_PACKET_CI); - rx_ci_rem = rx_ci % priv->rx_q_entries; if (skb) netif_receive_skb(skb);
Under heavy traffic, the BlueField Gigabit interface can become unresponsive. This is due to a possible race condition in the mlxbf_gige_rx_packet function, where the function exits with producer and consumer indices equal but there are remaining packet(s) to be processed. In order to prevent this situation, read receive consumer index *before* the HW replenish so that the mlxbf_gige_rx_packet function returns an accurate return value even if a packet is received into just-replenished buffer prior to exiting this routine. If the just-replenished buffer is received and occupies the last RX ring entry, the interface would not recover and instead would encounter RX packet drops related to internal buffer shortages since the driver RX logic is not being triggered to drain the RX ring. This patch will address and prevent this "ring full" condition. Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver") Reviewed-by: Asmaa Mnebhi <asmaa@nvidia.com> Signed-off-by: David Thompson <davthompson@nvidia.com> --- v2 * removed logic that affected RX_DMA enable/disable --- drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)