From 925147a92b6bd024c78c06fe939f16487499b0df Mon Sep 17 00:00:00 2001
From: Bernd Edlinger <bernd.edlinger@hotmail.de>
Date: Sat, 21 Oct 2017 06:51:30 +0000
Subject: [PATCH 07/24] stmmac: Don't access tx_q->dirty_tx before
 netif_tx_lock
Git-commit: 8d5f4b07174976c55a5f5d6967777373c6826944
Patch-mainline: v4.14-rc6
References: git-fixes

This is the possible reason for different hard to reproduce
problems on my ARMv7-SMP test system.

The symptoms are in recent kernels imprecise external aborts,
and in older kernels various kinds of network stalls and
unexpected page allocation failures.

My testing indicates that the trouble started between v4.5 and v4.6
and prevails up to v4.14.

Using the dirty_tx before acquiring the spin lock is clearly
wrong and was first introduced with v4.6.

Fixes: e3ad57c96715 ("stmmac: review RX/TX ring management")

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index d5a7f7804999..5053cf2b1b05 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1816,12 +1816,13 @@ static void stmmac_tx_clean(struct stmmac_priv *priv, u32 queue)
 {
 	struct stmmac_tx_queue *tx_q = &priv->tx_queue[queue];
 	unsigned int bytes_compl = 0, pkts_compl = 0;
-	unsigned int entry = tx_q->dirty_tx;
+	unsigned int entry;
 
 	netif_tx_lock(priv->dev);
 
 	priv->xstats.tx_clean++;
 
+	entry = tx_q->dirty_tx;
 	while (entry != tx_q->cur_tx) {
 		struct sk_buff *skb = tx_q->tx_skbuff[entry];
 		struct dma_desc *p;
-- 
2.16.4