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Date: Tue, 26 Aug 2014 17:48:25 +0200
From: Daniel Borkmann <dborkman@...hat.com>
To: alexander.h.duyck@...el.com
Cc: davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH net-next] ixgbe: flush when in xmit_more mode and under descriptor pressure
When xmit_more mode is being used and the ring is about to become
full, enforce a tail pointer write to the hw. Otherwise, we could
risk a Tx hang as pointed out by Alex.
Suggested-by: Alexander Duyck <alexander.h.duyck@...el.com>
Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
---
Hi Alex, something along that lines regarding your first comment?
drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 67 +++++++++++++++------------
1 file changed, 38 insertions(+), 29 deletions(-)
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index ba9ceaa..f851e84 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -6837,6 +6837,36 @@ static void ixgbe_tx_olinfo_status(union ixgbe_adv_tx_desc *tx_desc,
tx_desc->read.olinfo_status = cpu_to_le32(olinfo_status);
}
+static int __ixgbe_maybe_stop_tx(struct ixgbe_ring *tx_ring, u16 size)
+{
+ netif_stop_subqueue(tx_ring->netdev, tx_ring->queue_index);
+
+ /* Herbert's original patch had:
+ * smp_mb__after_netif_stop_queue();
+ * but since that doesn't exist yet, just open code it.
+ */
+ smp_mb();
+
+ /* We need to check again in a case another CPU has just
+ * made room available.
+ */
+ if (likely(ixgbe_desc_unused(tx_ring) < size))
+ return -EBUSY;
+
+ /* A reprieve! - use start_queue because it doesn't call schedule */
+ netif_start_subqueue(tx_ring->netdev, tx_ring->queue_index);
+ ++tx_ring->tx_stats.restart_queue;
+ return 0;
+}
+
+static inline int ixgbe_maybe_stop_tx(struct ixgbe_ring *tx_ring, u16 size)
+{
+ if (likely(ixgbe_desc_unused(tx_ring) >= size))
+ return 0;
+
+ return __ixgbe_maybe_stop_tx(tx_ring, size);
+}
+
#define IXGBE_TXD_CMD (IXGBE_TXD_CMD_EOP | \
IXGBE_TXD_CMD_RS)
@@ -6853,6 +6883,7 @@ static void ixgbe_tx_map(struct ixgbe_ring *tx_ring,
u32 tx_flags = first->tx_flags;
u32 cmd_type = ixgbe_tx_cmd_type(skb, tx_flags);
u16 i = tx_ring->next_to_use;
+ bool desc_pressure;
tx_desc = IXGBE_TX_DESC(tx_ring, i);
@@ -6958,10 +6989,15 @@ static void ixgbe_tx_map(struct ixgbe_ring *tx_ring,
tx_ring->next_to_use = i;
- if (!skb->xmit_more) {
+ desc_pressure = (ixgbe_desc_unused(tx_ring) < DESC_NEEDED);
+ if (!skb->xmit_more || unlikely(desc_pressure)) {
/* notify HW of packet */
ixgbe_write_tail(tx_ring, i);
+
+ if (unlikely(desc_pressure))
+ __ixgbe_maybe_stop_tx(tx_ring, DESC_NEEDED);
}
+
return;
dma_error:
dev_err(tx_ring->dev, "TX DMA map failed\n");
@@ -6978,6 +7014,7 @@ dma_error:
}
tx_ring->next_to_use = i;
+ ixgbe_maybe_stop_tx(tx_ring, DESC_NEEDED);
}
static void ixgbe_atr(struct ixgbe_ring *ring,
@@ -7068,32 +7105,6 @@ static void ixgbe_atr(struct ixgbe_ring *ring,
input, common, ring->queue_index);
}
-static int __ixgbe_maybe_stop_tx(struct ixgbe_ring *tx_ring, u16 size)
-{
- netif_stop_subqueue(tx_ring->netdev, tx_ring->queue_index);
- /* Herbert's original patch had:
- * smp_mb__after_netif_stop_queue();
- * but since that doesn't exist yet, just open code it. */
- smp_mb();
-
- /* We need to check again in a case another CPU has just
- * made room available. */
- if (likely(ixgbe_desc_unused(tx_ring) < size))
- return -EBUSY;
-
- /* A reprieve! - use start_queue because it doesn't call schedule */
- netif_start_subqueue(tx_ring->netdev, tx_ring->queue_index);
- ++tx_ring->tx_stats.restart_queue;
- return 0;
-}
-
-static inline int ixgbe_maybe_stop_tx(struct ixgbe_ring *tx_ring, u16 size)
-{
- if (likely(ixgbe_desc_unused(tx_ring) >= size))
- return 0;
- return __ixgbe_maybe_stop_tx(tx_ring, size);
-}
-
static u16 ixgbe_select_queue(struct net_device *dev, struct sk_buff *skb,
void *accel_priv, select_queue_fallback_t fallback)
{
@@ -7262,8 +7273,6 @@ xmit_fcoe:
#endif /* IXGBE_FCOE */
ixgbe_tx_map(tx_ring, first, hdr_len);
- ixgbe_maybe_stop_tx(tx_ring, DESC_NEEDED);
-
return NETDEV_TX_OK;
out_drop:
--
1.7.11.7
--
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