examples/eventdev: fix segment fault with generic pipeline

There was a segmentation fault when executing eventdev_pipeline with
command [1] with ConnectX-5 NIC card:

0x000000000079208c in rte_eth_tx_buffer (tx_pkt=0x16f8ed300, buffer=0x100,
                   queue_id=11, port_id=0) at
                   ../lib/ethdev/rte_ethdev.h:6636
txa_service_tx (txa=0x17b19d080, ev=0xffffffffe500, n=4) at
                   ../lib/eventdev/rte_event_eth_tx_adapter.c:631
0x0000000000792234 in txa_service_func (args=0x17b19d080) at
                   ../lib/eventdev/rte_event_eth_tx_adapter.c:666
0x00000000008b0784 in service_runner_do_callback (s=0x17fffe100,
                   cs=0x17ffb5f80, service_idx=2) at
                   ../lib/eal/common/rte_service.c:405
0x00000000008b0ad8 in service_run (i=2, cs=0x17ffb5f80,
                   service_mask=18446744073709551615, s=0x17fffe100,
                   serialize_mt_unsafe=0) at
                   ../lib/eal/common/rte_service.c:441
0x00000000008b0c68 in rte_service_run_iter_on_app_lcore (id=2,
                   serialize_mt_unsafe=0) at
                   ../lib/eal/common/rte_service.c:477
0x000000000057bcc4 in schedule_devices (lcore_id=0) at
                   ../examples/eventdev_pipeline/pipeline_common.h:138
0x000000000057ca94 in worker_generic_burst (arg=0x17b131e80) at
                   ../examples/eventdev_pipeline/
                   pipeline_worker_generic.c:83
0x00000000005794a8 in main (argc=11, argv=0xfffffffff470) at
                   ../examples/eventdev_pipeline/main.c:449

The root cause is that the queue_id (11) is invalid, the queue_id comes
from mbuf.hash.txadapter.txq which may pre-write by NIC driver when
receiving packets (e.g. pre-write mbuf.hash.fdir.hi field).

Because this example only enabled one ethdev queue, so fixes it by reset
txq to zero in the first worker stage.

[1] dpdk-eventdev_pipeline -l 0-48 --vdev event_sw0 -- -r1 -t1 -e1 -w ff0
    -s5 -n0 -c32 -W1000 -D
When launch eventdev_pipeline with command [1],  event_sw

Fixes: 81fb40f ("examples/eventdev: add generic worker pipeline")
Cc: [email protected]

Signed-off-by: Chengwen Feng <[email protected]>
Signed-off-by: Chenxingyu Wang <[email protected]>
Acked-by: Pavan Nikhilesh <[email protected]>

Author: fengchengwen

.mailmap

@@ -236,6 +236,7 @@ Cheng Peng <[email protected]>
 Chengwen Feng <[email protected]>
 Chenmin Sun <[email protected]>
 Chenming Chang <[email protected]>
+Chenxingyu Wang <[email protected]>
 Chenxu Di <[email protected]>
 Chenyu Huang <[email protected]>
 Cheryl Houser <[email protected]>

examples/eventdev_pipeline/pipeline_worker_generic.c

@@ -38,10 +38,12 @@ worker_generic(void *arg)
 		}
 		received++;
 
-		/* The first worker stage does classification */
-		if (ev.queue_id == cdata.qid[0])
+		/* The first worker stage does classification and sets txq. */
+		if (ev.queue_id == cdata.qid[0]) {
 			ev.flow_id = ev.mbuf->hash.rss
 						% cdata.num_fids;
+			rte_event_eth_tx_adapter_txq_set(ev.mbuf, 0);
+		}
 
 		ev.queue_id = cdata.next_qid[ev.queue_id];
 		ev.op = RTE_EVENT_OP_FORWARD;
@@ -96,10 +98,12 @@ worker_generic_burst(void *arg)
 
 		for (i = 0; i < nb_rx; i++) {
 
-			/* The first worker stage does classification */
-			if (events[i].queue_id == cdata.qid[0])
+			/* The first worker stage does classification and sets txq. */
+			if (events[i].queue_id == cdata.qid[0]) {
 				events[i].flow_id = events[i].mbuf->hash.rss
 							% cdata.num_fids;
+				rte_event_eth_tx_adapter_txq_set(events[i].mbuf, 0);
+			}
 
 			events[i].queue_id = cdata.next_qid[events[i].queue_id];
 			events[i].op = RTE_EVENT_OP_FORWARD;