From a7860992ed75eb11eb03e3919ca8de85d04f39d9 Mon Sep 17 00:00:00 2001
From: Robert Hancock <hancock@sedsystems.ca>
Date: Thu, 6 Jun 2019 16:28:17 -0600
Subject: [PATCH 27/35] net: axienet: Fix race condition causing TX hang
Git-commit: 7de44285c1f69ccfbe8be1d6a16fcd956681fee6
Patch-mainline: v5.3-rc1
References: git-fixes
It is possible that the interrupt handler fires and frees up space in
the TX ring in between checking for sufficient TX ring space and
stopping the TX queue in axienet_start_xmit. If this happens, the
queue wake from the interrupt handler will occur before the queue is
stopped, causing a lost wakeup and the adapter's transmit hanging.
To avoid this, after stopping the queue, check again whether there is
sufficient space in the TX ring. If so, wake up the queue again.
Signed-off-by: Robert Hancock <hancock@sedsystems.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index d853234ffafa..08658615971b 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -614,6 +614,10 @@ static void axienet_start_xmit_done(struct net_device *ndev)
ndev->stats.tx_packets += packets;
ndev->stats.tx_bytes += size;
+
+ /* Matches barrier in axienet_start_xmit */
+ smp_mb();
+
netif_wake_queue(ndev);
}
@@ -669,9 +673,19 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
cur_p = &lp->tx_bd_v[lp->tx_bd_tail];
if (axienet_check_tx_bd_space(lp, num_frag)) {
- if (!netif_queue_stopped(ndev))
- netif_stop_queue(ndev);
- return NETDEV_TX_BUSY;
+ if (netif_queue_stopped(ndev))
+ return NETDEV_TX_BUSY;
+
+ netif_stop_queue(ndev);
+
+ /* Matches barrier in axienet_start_xmit_done */
+ smp_mb();
+
+ /* Space might have just been freed - check again */
+ if (axienet_check_tx_bd_space(lp, num_frag))
+ return NETDEV_TX_BUSY;
+
+ netif_wake_queue(ndev);
}
if (skb->ip_summed == CHECKSUM_PARTIAL) {
--
2.16.4