[dpdk-dev] [PATCH v3] rte_ethdev: safer memory access by calling Rx/Tx callback

[Ananyev, Konstantin]

> -----Original Message-----
> From: ZY Qiu <quzeyao at gmail.com>
> Sent: Thursday, March 5, 2020 4:47 PM
> To: Thomas Monjalon <thomas at monjalon.net>; Yigit, Ferruh <ferruh.yigit at intel.com>; Andrew Rybchenko <arybchenko at solarflare.com>
> Cc: dev at dpdk.org; stephen at networkplumber.org; Ananyev, Konstantin <konstantin.ananyev at intel.com>; ZY Qiu
> <tgw_team at tencent.com>
> Subject: [PATCH v3] rte_ethdev: safer memory access by calling Rx/Tx callback
> 
> 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 at 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 {
> --

Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>

> 2.17.1