Re: [Intel-wired-lan] [PATCH net-next v3 03/13] net: introduce ndo_set_rx_mode_async and dev_rx_mode_work

Loktionov, Aleksandr
2026-03-20T07:13:42Z

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf
> Of Stanislav Fomichev
> Sent: Friday, March 20, 2026 2:25 AM
> To: netdev@vger.kernel.org
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> Subject: [Intel-wired-lan] [PATCH net-next v3 03/13] net: introduce
> ndo_set_rx_mode_async and dev_rx_mode_work
>
> Add ndo_set_rx_mode_async callback that drivers can implement instead
> of the legacy ndo_set_rx_mode. The legacy callback runs under the
> netif_addr_lock spinlock with BHs disabled, preventing drivers from
> sleeping. The async variant runs from a work queue with rtnl_lock and
> netdev_lock_ops held, in fully sleepable context.
>
> When __dev_set_rx_mode() sees ndo_set_rx_mode_async, it schedules
> dev_rx_mode_work instead of calling the driver inline. The work
> function takes two snapshots of each address list (uc/mc) under the
> addr_lock, then drops the lock and calls the driver with the work
> copies. After the driver returns, it reconciles the snapshots back to
> the real lists under the lock.
>
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
> Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
> ---
> Documentation/networking/netdevices.rst | 8 +++
> include/linux/netdevice.h | 20 ++++++
> net/core/dev.c | 95 +++++++++++++++++++++++-
> -
> 3 files changed, 116 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/networking/netdevices.rst
> b/Documentation/networking/netdevices.rst
> index 35704d115312..dc83d78d3b27 100644
> --- a/Documentation/networking/netdevices.rst
> +++ b/Documentation/networking/netdevices.rst
> @@ -289,6 +289,14 @@ struct net_device synchronization rules
> ndo_set_rx_mode:
> Synchronization: netif_addr_lock spinlock.
> Context: BHs disabled

...

> to
> +device
> + * and configure RX filtering.
> + * @dev: device
> + *
> + * When the device doesn't support unicast filtering it is put in
> +promiscuous
> + * mode while unicast addresses are present.
> */
> void __dev_set_rx_mode(struct net_device *dev) {
> const struct net_device_ops *ops = dev->netdev_ops;
>
> /* dev_open will call this function so the list will stay sane.
> */
> - if (!(dev->flags&IFF_UP))
> + if (!netif_up_and_present(dev))
> return;
>
> - if (!netif_device_present(dev))
> + if (ops->ndo_set_rx_mode_async) {
> + queue_work(rx_mode_wq, &dev->rx_mode_work);
> return;
This early return skips the legacy core fallback below.
Before this patch, __dev_set_rx_mode() continued into the
existing unicast-filter handling when the device did not
advertise IFF_UNICAST_FLT.

After this patch, any driver that implements
ndo_set_rx_mode_async but does not set IFF_UNICAST_FLT
will never hit that fallback path.

+ }
>
> if (!(dev->priv_flags & IFF_UNICAST_FLT)) {
> /* Unicast addresses changes may only happen under the
> rtnl, @@ -11708,6 +11772,16 @@ void netdev_run_todo(void)
>
> __rtnl_unlock();
>

...

> open_softirq(NET_TX_SOFTIRQ, net_tx_action);
> open_softirq(NET_RX_SOFTIRQ, net_rx_action);
>
> --
> 2.53.0