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authorElad Kanfi <eladkan@mellanox.com>2016-05-09 20:13:19 +0300
committerDavid S. Miller <davem@davemloft.net>2016-05-10 15:04:49 -0400
commite5df49d564fe993c68f5cff6d96972a6358b4958 (patch)
tree899ce25dfc99e15b7454b845a894dabfd4e3d1dd
parentd99079e2fbd5ac38884f498ca99435d525152a88 (diff)
downloadlinux-e5df49d564fe993c68f5cff6d96972a6358b4958.tar.gz
net: nps_enet: Tx handler synchronization
Below is a description of a possible problematic sequence. CPU-A is sending a frame and CPU-B handles the interrupt that indicates the frame was sent. CPU-B reads an invalid value of tx_packet_sent. CPU-A CPU-B ----- ----- nps_enet_send_frame . . tx_skb = skb tx_packet_sent = true order HW to start tx . . HW complete tx ------> get tx complete interrupt . . if(tx_packet_sent == true) handle tx_skb end memory transaction (tx_packet_sent actually written) Furthermore there is a dependency between tx_skb and tx_packet_sent. There is no assurance that tx_skb contains a valid pointer at CPU B when it sees tx_packet_sent == true. Solution: Initialize tx_skb to NULL and use it to indicate that packet was sent, in this way tx_packet_sent can be removed. Add a write memory barrier after setting tx_skb in order to make sure that it is valid before HW is informed and IRQ is fired. Fixed sequence will be: CPU-A CPU-B ----- ----- tx_skb = skb wmb() . . order HW to start tx . . HW complete tx ------> get tx complete interrupt . . if(tx_skb != NULL) handle tx_skb tx_skb = NULL Signed-off-by: Elad Kanfi <eladkan@mellanox.com> Acked-by: Noam Camus <noamca@mellanox.com> Acked-by: Gilad Ben-Yossef <giladby@mellanox.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/ethernet/ezchip/nps_enet.c15
-rw-r--r--drivers/net/ethernet/ezchip/nps_enet.h2
2 files changed, 9 insertions, 8 deletions
diff --git a/drivers/net/ethernet/ezchip/nps_enet.c b/drivers/net/ethernet/ezchip/nps_enet.c
index 1f23845a0694..25ac2def08ce 100644
--- a/drivers/net/ethernet/ezchip/nps_enet.c
+++ b/drivers/net/ethernet/ezchip/nps_enet.c
@@ -145,7 +145,7 @@ static void nps_enet_tx_handler(struct net_device *ndev)
u32 tx_ctrl_nt = (tx_ctrl_value & TX_CTL_NT_MASK) >> TX_CTL_NT_SHIFT;
/* Check if we got TX */
- if (!priv->tx_packet_sent || tx_ctrl_ct)
+ if (!priv->tx_skb || tx_ctrl_ct)
return;
/* Ack Tx ctrl register */
@@ -160,7 +160,7 @@ static void nps_enet_tx_handler(struct net_device *ndev)
}
dev_kfree_skb(priv->tx_skb);
- priv->tx_packet_sent = false;
+ priv->tx_skb = NULL;
if (netif_queue_stopped(ndev))
netif_wake_queue(ndev);
@@ -217,7 +217,7 @@ static irqreturn_t nps_enet_irq_handler(s32 irq, void *dev_instance)
u32 tx_ctrl_ct = (tx_ctrl_value & TX_CTL_CT_MASK) >> TX_CTL_CT_SHIFT;
u32 rx_ctrl_cr = (rx_ctrl_value & RX_CTL_CR_MASK) >> RX_CTL_CR_SHIFT;
- if ((!tx_ctrl_ct && priv->tx_packet_sent) || rx_ctrl_cr)
+ if ((!tx_ctrl_ct && priv->tx_skb) || rx_ctrl_cr)
if (likely(napi_schedule_prep(&priv->napi))) {
nps_enet_reg_set(priv, NPS_ENET_REG_BUF_INT_ENABLE, 0);
__napi_schedule(&priv->napi);
@@ -387,8 +387,6 @@ static void nps_enet_send_frame(struct net_device *ndev,
/* Write the length of the Frame */
tx_ctrl_value |= length << TX_CTL_NT_SHIFT;
- /* Indicate SW is done */
- priv->tx_packet_sent = true;
tx_ctrl_value |= NPS_ENET_ENABLE << TX_CTL_CT_SHIFT;
/* Send Frame */
nps_enet_reg_set(priv, NPS_ENET_REG_TX_CTL, tx_ctrl_value);
@@ -465,7 +463,7 @@ static s32 nps_enet_open(struct net_device *ndev)
s32 err;
/* Reset private variables */
- priv->tx_packet_sent = false;
+ priv->tx_skb = NULL;
priv->ge_mac_cfg_2_value = 0;
priv->ge_mac_cfg_3_value = 0;
@@ -534,6 +532,11 @@ static netdev_tx_t nps_enet_start_xmit(struct sk_buff *skb,
priv->tx_skb = skb;
+ /* make sure tx_skb is actually written to the memory
+ * before the HW is informed and the IRQ is fired.
+ */
+ wmb();
+
nps_enet_send_frame(ndev, skb);
return NETDEV_TX_OK;
diff --git a/drivers/net/ethernet/ezchip/nps_enet.h b/drivers/net/ethernet/ezchip/nps_enet.h
index d0cab600bce8..3939ca20cc9f 100644
--- a/drivers/net/ethernet/ezchip/nps_enet.h
+++ b/drivers/net/ethernet/ezchip/nps_enet.h
@@ -165,14 +165,12 @@
* struct nps_enet_priv - Storage of ENET's private information.
* @regs_base: Base address of ENET memory-mapped control registers.
* @irq: For RX/TX IRQ number.
- * @tx_packet_sent: SW indication if frame is being sent.
* @tx_skb: socket buffer of sent frame.
* @napi: Structure for NAPI.
*/
struct nps_enet_priv {
void __iomem *regs_base;
s32 irq;
- bool tx_packet_sent;
struct sk_buff *tx_skb;
struct napi_struct napi;
u32 ge_mac_cfg_2_value;