Re: [PATCH] net/ring: remove internal devarg

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue, 22 Sep 2026 12:36:14 +0100
Bruce Richardson <bruce.richardson@intel.com> wrote:

> The devarg "internal" was used to pass a pointer to the creation
> function to reuse set parameters. However, this meant it could also be
> used as a devarg on the commandline leading to incorrect behaviour.
> Redesign the passing of the args parameters to use a per-thread global
> instead. The wrapper function sets the global to a valid value before
> calling the main creation function, skipping passing a devarg, before
> resetting the pointer back to NULL when the function returns.
> 
> Bugzilla ID: 1687
> Fixes: 96cb19521147 ("net/ring: use EAL APIs in PMD specific API")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> ---

Minor nits from Opus review:

Review: [PATCH] net/ring: remove internal devarg
Patchwork: 169914

Applies cleanly to main, builds with -Dwerror=true. Fixes tag hash
96cb19521147 verified. Removing a user-reachable devarg that is
dereferenced as a raw pointer is the right fix.

Warning

The per-lcore pointer is still set while user callbacks run.
do_eth_dev_ring_create() calls rte_eth_dev_probing_finish(), which
fires RTE_ETH_EVENT_NEW callbacks synchronously on the same thread.
If a callback calls rte_vdev_init("net_ring_foo", "nodeaction=...")
the nested probe sees eth_ring_internal_args != NULL, ignores the
user's devargs, and attaches net_ring_foo to the outer caller's
rings.

Clear the pointer in probe right after reading it:

	internal_args = RTE_PER_LCORE(eth_ring_internal_args);
	RTE_PER_LCORE(eth_ring_internal_args) = NULL;
	if (internal_args != NULL) {

Keep the reset after rte_vdev_init() in rte_eth_from_rings() to
cover the paths where probe is never reached (-EEXIST, no driver
match). This also makes the comment "consumed and cleared by probe"
true; as written, probe does not clear it.

Alternatively add the vdev name to struct ring_internal_args and
require a match in probe. Either works; clearing is simpler.

Info

No test coverage. app/test/test_pmd_ring.c could add a case that
"net_ring_x,internal=0x1" no longer dereferences the value (it now
falls into the "Ignoring unsupported parameters" path).

Double space before "*/" in the comment above
RTE_DEFINE_PER_LCORE.