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

[Stanislav Fomichev <stfomichev@gmail.com>]

On 03/20, Loktionov, Aleksandr wrote:
> 
> 
> > -----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
> > Cc: davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> > pabeni@redhat.com; horms@kernel.org; corbet@lwn.net;
> > skhan@linuxfoundation.org; andrew+netdev@lunn.ch;
> > michael.chan@broadcom.com; pavan.chebbi@broadcom.com; Nguyen, Anthony
> > L <anthony.l.nguyen@intel.com>; Kitszel, Przemyslaw
> > <przemyslaw.kitszel@intel.com>; saeedm@nvidia.com; tariqt@nvidia.com;
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> > Jacob E <jacob.e.keller@intel.com>; willemb@google.com;
> > skhawaja@google.com; bestswngs@gmail.com; Loktionov, Aleksandr
> > <aleksandr.loktionov@intel.com>; kees@kernel.org; linux-
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> > wireless@vger.kernel.org; linux-kselftest@vger.kernel.org;
> > leon@kernel.org
> > 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.

I believe this is addressed later in "net: move promiscuity handling into
dev_rx_mode_work"? That should take care of doing __dev_set_promiscuity
for !IFF_UNICAST_FLT+ndo_set_rx_mode_async. Not sure if there is a
better way to rearrange the chunks in the patches.

        if (ops->ndo_set_rx_mode_async) {
                ...

+		promisc_inc = dev_uc_promisc_update(dev);
+
+		netif_addr_unlock_bh(dev);
+	} else {
+		netif_addr_lock_bh(dev);
+		promisc_inc = dev_uc_promisc_update(dev);
+		netif_addr_unlock_bh(dev);
+	}
+
+	if (promisc_inc)
+		__dev_set_promiscuity(dev, promisc_inc, false);
+