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From: ZY Qiu <quzeyao@gmail.com>
X-Google-Original-From: ZY Qiu <tgw_team@tencent.com>
To: Thomas Monjalon <thomas@monjalon.net>,
 Ferruh Yigit <ferruh.yigit@intel.com>,
 Andrew Rybchenko <arybchenko@solarflare.com>
Cc: dev@dpdk.org, stephen@networkplumber.org, konstantin.ananyev@intel.com,
 ZY Qiu <tgw_team@tencent.com>
Date: Fri,  6 Mar 2020 00:47:04 +0800
Message-Id: <20200305164704.29900-1-tgw_team@tencent.com>
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References: <20200304173349.26459-1-tgw_team@tencent.com>
Subject: [dpdk-dev] [PATCH v3] rte_ethdev: safer memory access by calling
	Rx/Tx callback
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When compiling with -O0,
the compiler does not optimize two memory accesses into one.
Leads to accessing a null pointer when queue post Rx burst callback
removal while traffic is running.

Signed-off-by: ZY Qiu <tgw_team@tencent.com>
---
 lib/librte_ethdev/rte_ethdev.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
index d1a593ad1..c46612e3e 100644
--- a/lib/librte_ethdev/rte_ethdev.h
+++ b/lib/librte_ethdev/rte_ethdev.h
@@ -4388,10 +4388,10 @@ rte_eth_rx_burst(uint16_t port_id, uint16_t queue_id,
 				     rx_pkts, nb_pkts);
 
 #ifdef RTE_ETHDEV_RXTX_CALLBACKS
-	if (unlikely(dev->post_rx_burst_cbs[queue_id] != NULL)) {
-		struct rte_eth_rxtx_callback *cb =
-				dev->post_rx_burst_cbs[queue_id];
+	struct rte_eth_rxtx_callback *volatile cb =
+			dev->post_rx_burst_cbs[queue_id];
 
+	if (unlikely(cb != NULL)) {
 		do {
 			nb_rx = cb->fn.rx(port_id, queue_id, rx_pkts, nb_rx,
 						nb_pkts, cb->param);
@@ -4652,7 +4652,8 @@ rte_eth_tx_burst(uint16_t port_id, uint16_t queue_id,
 #endif
 
 #ifdef RTE_ETHDEV_RXTX_CALLBACKS
-	struct rte_eth_rxtx_callback *cb = dev->pre_tx_burst_cbs[queue_id];
+	struct rte_eth_rxtx_callback *volatile cb =
+			dev->pre_tx_burst_cbs[queue_id];
 
 	if (unlikely(cb != NULL)) {
 		do {
-- 
2.17.1