Re: [PATCH iwl-net 3/3] ice: do not block on the aux device lock in ndo_setup_tc

[Petr Oros <poros@redhat.com>]

On 10/21/26 1:22 PM, Loktionov, Aleksandr wrote:
> 
> 
>> -----Original Message-----
>> From: Petr Oros <poros@redhat.com>
>> Sent: Monday, October 19, 2026 8:53 AM
>> To: netdev@vger.kernel.org
>> Cc: Oros, Petr <poros@redhat.com>; Nguyen, Anthony L
>> <anthony.l.nguyen@intel.com>; Kitszel, Przemyslaw
>> <przemyslaw.kitszel@intel.com>; Andrew Lunn <andrew+netdev@lunn.ch>;
>> David S . Miller <davem@davemloft.net>; Eric Dumazet
>> <edumazet@kernel.org>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni
>> <pabeni@redhat.com>; Ertman, David M <david.m.ertman@intel.com>; Shiraz
>> Saleem <shiraz.saleem@intel.com>; Leon Romanovsky <leon@kernel.org>;
>> Maziarz, Kamil <kamil.maziarz@intel.com>; Rafal Rogalski
>> <rafalx.rogalski@intel.com>; Loktionov, Aleksandr
>> <aleksandr.loktionov@intel.com>; Schmidt, Michal <mschmidt@redhat.com>;
>> linux-rdma@vger.kernel.org; intel-wired-lan@lists.osuosl.org; linux-
>> kernel@vger.kernel.org; stable@vger.kernel.org; Sebastian Andrzej
>> Siewior <bigeasy@linutronix.de>; Clark Williams <clrkwllms@kernel.org>;
>> Steven Rostedt <rostedt@goodmis.org>; Mateusz Palczewski
>> <mateusz.palczewski@intel.com>; linux-rt-devel@lists.linux.dev
>> Subject: [PATCH iwl-net 3/3] ice: do not block on the aux device lock in
>> ndo_setup_tc
>>
>> The TC_SETUP_QDISC_MQPRIO path of ice_setup_tc() takes the auxiliary
>> device lock to test whether the RDMA driver is bound, and ndo_setup_tc()
>> runs with the RTNL lock held. This closes the same cycle against the
>> RDMA auxiliary probe as the two preceding patches.
>>
>> Use device_trylock() and report the device as busy when it fails, with a
>> distinct message for the same reason as in the previous patch.
>>
>> Fixes: 4b31fd4d77ff ("ice: Fix RDMA VSI removal during queue rebuild")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Petr Oros <poros@redhat.com>
>> ---
>>   drivers/net/ethernet/intel/ice/ice_main.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/intel/ice/ice_main.c
>> b/drivers/net/ethernet/intel/ice/ice_main.c
>> index edb62606d2aae3..7b251136149615 100644
>> --- a/drivers/net/ethernet/intel/ice/ice_main.c
>> +++ b/drivers/net/ethernet/intel/ice/ice_main.c
>> @@ -9448,7 +9448,11 @@ ice_setup_tc(struct net_device *netdev, enum
>> tc_setup_type type,
>>   		cdev = pf->cdev_info;
>>   		if (cdev && cdev->adev) {
>>   			mutex_lock(&pf->adev_mutex);
>> -			device_lock(&cdev->adev->dev);
>> +			if (!device_trylock(&cdev->adev->dev)) {
>> +				mutex_unlock(&pf->adev_mutex);
>> +				netdev_dbg(netdev, "RDMA auxiliary device is
>> busy, try again\n");
>> +				return -EBUSY;
> You return error here, but it looks like being silently dropped in mqprio_disable_offload() isn't it ?

Yes, mqprio_disable_offload() ignores it, the same as it ignores the
existing -EBUSY for a bound RDMA driver. Blocking there brings the
deadlock back and skipping the lock races with the probe, so v2 keeps
the refusal and warns about it instead of netdev_dbg().

> 
>> +			}
>>   			locked = true;
>>   			if (cdev->adev->dev.driver) {
>>   				netdev_err(netdev, "Cannot change qdisc when
>> RDMA is active\n");
>> --
>> 2.56.0
>