[dpdk-dev] [PATCH v2] rte_ethdev: safer memory access by calling Rx callback

[ZY Qiu <quzeyao@gmail.com>]

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.
See rte_eth_tx_burst function.

Signed-off-by: ZY Qiu <tgw_team@tencent.com>
---
 lib/librte_ethdev/rte_ethdev.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
index d1a593ad1..35eb580ff 100644
--- a/lib/librte_ethdev/rte_ethdev.h
+++ b/lib/librte_ethdev/rte_ethdev.h
@@ -4388,10 +4388,8 @@ 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 *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);
-- 
2.17.1