[dpdk-dev] [PATCH v2] eventdev: fix Rx adapter stalls on event device backpressure

[Jayatheerthan, Jay]

Looks good. Thanks for posting this change!

Acked-by: Jay Jayatheerthan <jay.jayatheerthan at intel.com>

> -----Original Message-----
> From: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
> Sent: Wednesday, November 10, 2021 4:44 PM
> To: jerinjacobk at gmail.com; Jayatheerthan, Jay <jay.jayatheerthan at intel.com>; Kundapura, Ganapati
> <ganapati.kundapura at intel.com>; jerinj at marvell.com
> Cc: dev @ dpdk . org <dev at dpdk.org>; mattias.ronnblom <mattias.ronnblom at ericsson.com>
> Subject: [PATCH v2] eventdev: fix Rx adapter stalls on event device backpressure
> 
> In the Eventdev Ethernet RX Adapter, correctly handle the case where
> the circular enqueue buffer head and last index point to the same
> element.
> 
> This bug may be triggered in case there is backpressure from the event
> device to the RX adapter.
> 
> v2:
> * Corrected bug description
> 
> Fixes: 8113fd15e229 ("eventdev/eth_rx: make enqueue buffer circular")
> Cc: ganapati.kundapura at intel.com
> 
> Signed-off-by: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
> ---
>  lib/eventdev/rte_event_eth_rx_adapter.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/eventdev/rte_event_eth_rx_adapter.c b/lib/eventdev/rte_event_eth_rx_adapter.c
> index 56318b5a6f..809416d9b7 100644
> --- a/lib/eventdev/rte_event_eth_rx_adapter.c
> +++ b/lib/eventdev/rte_event_eth_rx_adapter.c
> @@ -777,19 +777,25 @@ rxa_flush_event_buffer(struct event_eth_rx_adapter *rx_adapter,
>  		       struct eth_event_enqueue_buffer *buf,
>  		       struct rte_event_eth_rx_adapter_stats *stats)
>  {
> -	uint16_t count = buf->last ? buf->last - buf->head : buf->count;
> +	uint16_t count = buf->count;
> +	uint16_t n = 0;
> 
>  	if (!count)
>  		return 0;
> 
> -	uint16_t n = rte_event_enqueue_new_burst(rx_adapter->eventdev_id,
> -					rx_adapter->event_port_id,
> -					&buf->events[buf->head],
> -					count);
> -	if (n != count)
> -		stats->rx_enq_retry++;
> +	if (buf->last)
> +		count = buf->last - buf->head;
> +
> +	if (count) {
> +		n = rte_event_enqueue_new_burst(rx_adapter->eventdev_id,
> +						rx_adapter->event_port_id,
> +						&buf->events[buf->head],
> +						count);
> +		if (n != count)
> +			stats->rx_enq_retry++;
> 
> -	buf->head += n;
> +		buf->head += n;
> +	}
> 
>  	if (buf->last && n == count) {
>  		uint16_t n1;
> --
> 2.25.1