[PATCH iwl-net v2 2/5] ice: take tc_mutex before the auxiliary device locks in ndo_setup_tc

[Petr Oros <poros@redhat.com>]

The mqprio path of ice_setup_tc() takes pf->adev_mutex and the auxiliary
device lock first and pf->tc_mutex after them. The dcbnl handlers take
pf->tc_mutex first and reach pf->adev_mutex through ice_pf_dcb_cfg() and
ice_send_event_to_aux(). Both run with the RTNL lock held, so the two
orders do not deadlock against each other, but they form a circular
dependency for lockdep, and the DCB reconfiguration is about to hold
pf->adev_mutex for longer.

Take pf->tc_mutex first, which is the order the dcbnl side has used
since pf->adev_mutex was introduced.

Fixes: 4b31fd4d77ff ("ice: Fix RDMA VSI removal during queue rebuild")
Signed-off-by: Petr Oros <poros@redhat.com>
---
v2:
- new patch, ice_setup_tc() took pf->adev_mutex before pf->tc_mutex
  while the dcbnl handlers take them the other way round
---
 drivers/net/ethernet/intel/ice/ice_main.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
index 984479f1e1f6d9..8693ca285d5f1e 100644
--- a/drivers/net/ethernet/intel/ice/ice_main.c
+++ b/drivers/net/ethernet/intel/ice/ice_main.c
@@ -9438,6 +9438,8 @@ ice_setup_tc(struct net_device *netdev, enum tc_setup_type type,
 			return -EOPNOTSUPP;
 		}
 
+		mutex_lock(&pf->tc_mutex);
+
 		cdev = pf->cdev_info;
 		if (cdev) {
 			mutex_lock(&pf->adev_mutex);
@@ -9456,15 +9458,14 @@ ice_setup_tc(struct net_device *netdev, enum tc_setup_type type,
 		}
 
 		/* setup traffic classifier for receive side */
-		mutex_lock(&pf->tc_mutex);
 		err = ice_setup_tc_mqprio_qdisc(netdev, type_data);
-		mutex_unlock(&pf->tc_mutex);
 
 adev_unlock:
 		if (locked) {
 			device_unlock(&adev->dev);
 			mutex_unlock(&pf->adev_mutex);
 		}
+		mutex_unlock(&pf->tc_mutex);
 		return err;
 	case TC_SETUP_QDISC_ETF:
 		return ice_offload_txtime(netdev, type_data);
-- 
2.56.0