From e5df49d564fe993c68f5cff6d96972a6358b4958 Mon Sep 17 00:00:00 2001 From: Elad Kanfi Date: Mon, 9 May 2016 20:13:19 +0300 Subject: 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 Acked-by: Noam Camus Acked-by: Gilad Ben-Yossef Signed-off-by: David S. Miller --- drivers/net/ethernet/ezchip/nps_enet.c | 15 +++++++++------ drivers/net/ethernet/ezchip/nps_enet.h | 2 -- 2 files changed, 9 insertions(+), 8 deletions(-) (limited to 'drivers/net/ethernet/ezchip') 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; -- cgit v1.2.3