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

[Petr Oros <poros@redhat.com>]

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@redhat.com>
---
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@redhat.com/
---
 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