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

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 11 Jun 2026 17:49:23 +0200
Maxime Leroy <maxime@leroys.fr> wrote:

> 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@dpdk.org
> Signed-off-by: Maxime Leroy <maxime@leroys.fr>

I wonder if queue_count dummy should just return 0 instead of -NOTSUP.
There are never going to be packets in the queue to receive.

Ditto for transmit and the status routines.