[PATCH 8/9] ethdev: keep fast-path ops valid after port stop

[Maxime Leroy]

eth_dev_fp_ops_reset() restores a port's fast-path ops on stop/release
via a compound literal, so every field it omits is zeroed to NULL. It
sets only rx_pkt_burst/tx_pkt_burst (and the rxq/txq data), leaving
rx_queue_count, tx_queue_count, rx/tx_descriptor_status, tx_pkt_prepare
and the recycle callbacks NULL.

In non-debug builds these ops are reached through an unguarded indirect
call (the NULL check exists only under RTE_ETHDEV_DEBUG_RX/TX). So a
thread calling e.g. rte_eth_rx_queue_count() on a port being stopped
dereferences NULL and crashes, while the same race on rte_eth_rx_burst()
is harmless because the burst ops are reset to dummies. A poll-mode
worker re-checking rx_queue_count before arming the Rx interrupt and
sleeping hits exactly this.

Reset these ops to the same dummies eth_dev_set_dummy_fops() installs,
so a stopped port behaves like a freshly allocated one: every fast-path
op is a safe no-op, none is NULL.

Fixes: 066f3d9cc21c ("ethdev: remove callback checks from fast path")
Cc: stable at dpdk.org
Signed-off-by: Maxime Leroy <maxime at leroys.fr>
---
 lib/ethdev/ethdev_private.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/ethdev/ethdev_private.c b/lib/ethdev/ethdev_private.c
index 72a0723846..75ea3eedff 100644
--- a/lib/ethdev/ethdev_private.c
+++ b/lib/ethdev/ethdev_private.c
@@ -263,6 +263,13 @@ eth_dev_fp_ops_reset(struct rte_eth_fp_ops *fpo)
 	*fpo = (struct rte_eth_fp_ops) {
 		.rx_pkt_burst = dummy_eth_rx_burst,
 		.tx_pkt_burst = dummy_eth_tx_burst,
+		.tx_pkt_prepare = rte_eth_tx_pkt_prepare_dummy,
+		.rx_queue_count = rte_eth_queue_count_dummy,
+		.tx_queue_count = rte_eth_queue_count_dummy,
+		.rx_descriptor_status = rte_eth_descriptor_status_dummy,
+		.tx_descriptor_status = rte_eth_descriptor_status_dummy,
+		.recycle_tx_mbufs_reuse = rte_eth_recycle_tx_mbufs_reuse_dummy,
+		.recycle_rx_descriptors_refill = rte_eth_recycle_rx_descriptors_refill_dummy,
 		.rxq = {
 			.data = (void **)&dummy_queues_array[port_id],
 			.clbk = dummy_data,
-- 
2.43.0