RE: [PATCH iwl-net v2 4/5] ice: do not block on the aux device lock in ethtool set_channels

[Loktionov, Aleksandr]

> -----Original Message-----
> From: Petr Oros <poros@xxxxxxxxxx>
> Sent: Friday, October 23, 2026 9:03 AM
> To: netdev@xxxxxxxxxxxxxxx
> Cc: Oros, Petr <poros@xxxxxxxxxx>; Nguyen, Anthony L
> <anthony.l.nguyen@xxxxxxxxx>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@xxxxxxxxx>; Andrew Lunn <andrew+netdev@xxxxxxx>;
> David S. Miller <davem@xxxxxxxxxxxxx>; Eric Dumazet
> <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo Abeni
> <pabeni@xxxxxxxxxx>; Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>;
> Clark Williams <clrkwllms@xxxxxxxxxx>; Steven Rostedt
> <rostedt@xxxxxxxxxxx>; Ertman, David M <david.m.ertman@xxxxxxxxx>;
> Mateusz Palczewski <mateusz.palczewski@xxxxxxxxx>; Leon Romanovsky
> <leon@xxxxxxxxxx>; Rafal Rogalski <rafalx.rogalski@xxxxxxxxx>; Shiraz
> Saleem <shiraz.saleem@xxxxxxxxx>; Loktionov, Aleksandr
> <aleksandr.loktionov@xxxxxxxxx>; intel-wired-lan@xxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; linux-rt-devel@xxxxxxxxxxxxxxx
> Subject: [PATCH iwl-net v2 4/5] ice: do not block on the aux device lock
> in ethtool set_channels
> 
> ice_set_channels() takes the auxiliary device lock to test whether the
> RDMA driver is bound, and ethtool ops run with the RTNL lock held. This
> is the same inversion against the RDMA auxiliary probe as the one fixed
> in ice_send_event_to_aux(), reached through a different caller.
> 
> Use device_trylock() and report the device as busy when it fails. The
> existing diagnostic is not reused, a contended lock does not mean the
> RDMA driver is bound. It is a netdev_dbg(), the condition is transient
> and userspace already learns about it from -EBUSY.
> 
> Fixes: a6a0974aae42 ("ice: Prevent set_channel from changing queues
> while RDMA active")
> Signed-off-by: Petr Oros <poros@xxxxxxxxxx>
> ---
> v2:
> - rebased on the new patches 1 and 2, the trylock now sits inside the
>   pointer test done under adev_mutex
> 
> v1: https://lore.kernel.org/all/20261019065301.3983537-3-
> poros@xxxxxxxxxx/
> ---
>  drivers/net/ethernet/intel/ice/ice_ethtool.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool.c
> b/drivers/net/ethernet/intel/ice/ice_ethtool.c
> index 5482a64c81c95a..dbc662d6233957 100644
> --- a/drivers/net/ethernet/intel/ice/ice_ethtool.c
> +++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c
> @@ -3947,7 +3947,11 @@ static int ice_set_channels(struct net_device
> *dev, struct ethtool_channels *ch)
>  		mutex_lock(&pf->adev_mutex);
>  		adev = pf->cdev_info->adev;
>  		if (adev) {
> -			device_lock(&adev->dev);
> +			if (!device_trylock(&adev->dev)) {
> +				mutex_unlock(&pf->adev_mutex);
> +				netdev_dbg(dev, "RDMA auxiliary device is
> busy, try again\n");
> +				return -EBUSY;
> +			}
>  			locked = true;
>  			if (adev->dev.driver) {
>  				netdev_err(dev, "Cannot change channels when
> RDMA is active\n");
> --
> 2.56.0

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@xxxxxxxxx>