> -----Original Message-----
> From: Petr Oros <[email protected]>
> Sent: Monday, October 19, 2026 8:53 AM
> To: [email protected]
> Cc: Oros, Petr <[email protected]>; Nguyen, Anthony L
> <[email protected]>; Kitszel, Przemyslaw
> <[email protected]>; Andrew Lunn <[email protected]>;
> David S . Miller <[email protected]>; Eric Dumazet
> <[email protected]>; Jakub Kicinski <[email protected]>; Paolo Abeni
> <[email protected]>; Ertman, David M <[email protected]>; Shiraz
> Saleem <[email protected]>; Leon Romanovsky <[email protected]>;
> Maziarz, Kamil <[email protected]>; Rafal Rogalski
> <[email protected]>; Loktionov, Aleksandr
> <[email protected]>; Schmidt, Michal <[email protected]>;
> [email protected]; [email protected]; linux-
> [email protected]; [email protected]; Sebastian Andrzej
> Siewior <[email protected]>; Clark Williams <[email protected]>;
> Steven Rostedt <[email protected]>; Mateusz Palczewski
> <[email protected]>; [email protected]
> Subject: [PATCH iwl-net 1/3] ice: avoid RTNL deadlock when notifying the
> RDMA auxiliary driver
>
> ice_send_event_to_aux() blocks on the auxiliary device lock, and the
> dcbnl callers reach it with the RTNL lock held. The RDMA auxiliary probe
> takes the two in the opposite order, because __driver_attach() holds the
> auxiliary device lock across ib_register_device(), which needs the RTNL
> lock:
>
> systemd-udevd state:D
> really_probe <- holds device_lock(&adev->dev)
> icrdma_probe
> irdma_ib_register_device
> ib_register_device
> setup_device
> irdma_roce_port_immutable
> ib_query_port
> irdma_query_port
> ib_get_eth_speed <- blocks on rtnl_lock()
>
> lldpad state:D
> rtnetlink_rcv_msg <- holds rtnl_lock()
> dcb_doit
> dcbnl_ieee_set
> ice_dcbnl_setets
> ice_pf_dcb_cfg
> ice_send_event_to_aux <- blocks on device_lock(&adev->dev)
>
> Everything else that needs the RTNL lock piles up behind lldpad and the
> boot never completes. The probe side cannot be changed, so use
> device_trylock() and report whether the event reached the driver.
>
> IIDC_RDMA_EVENT_BEFORE_TC_CHANGE has to arrive before the traffic
> classes change, so ice_pf_dcb_cfg() refuses the request with -EBUSY
> rather than run it behind the RDMA driver's back. The critical error and
> MTU change events are sent from the service task, which consumes their
> pending bits before sending, so those are re-armed instead.
> AFTER_TC_CHANGE keeps its fire and forget behaviour, it can be neither
> refused, the hardware has already changed, nor deferred, every lock that
> would serialise a deferred delivery against the dcbnl callers forms
> another cycle.
>
> Fixes: 348048e724a0 ("ice: Implement iidc operations")
> Cc: [email protected]
> Signed-off-by: Petr Oros <[email protected]>
> ---
> drivers/net/ethernet/intel/ice/ice_dcb_lib.c | 9 ++++++++-
> drivers/net/ethernet/intel/ice/ice_idc.c | 20 ++++++++++++++++----
> drivers/net/ethernet/intel/ice/ice_idc_int.h | 2 +-
> drivers/net/ethernet/intel/ice/ice_main.c | 16 ++++++++++++----
> 4 files changed, 37 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> b/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> index 0bc6dd37568792..2022b46c990cb2 100644
> --- a/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_dcb_lib.c
> @@ -355,8 +355,10 @@ int ice_pf_dcb_cfg(struct ice_pf *pf, struct
> ice_dcbx_cfg *new_cfg, bool locked)
> struct iidc_rdma_event *event;
> int ret = ICE_DCB_NO_HW_CHG;
> struct ice_vsi *pf_vsi;
> + bool dcb_ena;
>
> curr_cfg = &pf->hw.port_info->qos_cfg.local_dcbx_cfg;
> + dcb_ena = test_bit(ICE_FLAG_DCB_ENA, pf->flags);
>
> /* FW does not care if change happened */
> if (!pf->hw.port_info->qos_cfg.is_sw_lldp)
> @@ -406,7 +408,12 @@ int ice_pf_dcb_cfg(struct ice_pf *pf, struct
> ice_dcbx_cfg *new_cfg, bool locked)
> }
>
> set_bit(IIDC_RDMA_EVENT_BEFORE_TC_CHANGE, event->type);
> - ice_send_event_to_aux(pf, event);
> + if (!ice_send_event_to_aux(pf, event)) {
> + assign_bit(ICE_FLAG_DCB_ENA, pf->flags, dcb_ena);
> + kfree(event);
> + ret = -EBUSY;
-EBUSY doesn't match to any ICE_DCB_* constant, are you sure you tested this
case?
It looks like it will be processed like ICE_DCB_NO_HW_CHG i.e. no change
needed, isn't it?
> + goto free_cfg;
> + }
> kfree(event);
>
> /* avoid race conditions by holding the lock while disabling and
> diff --git a/drivers/net/ethernet/intel/ice/ice_idc.c
> b/drivers/net/ethernet/intel/ice/ice_idc.c
> index 102d63c3018b1f..7fd35ce966ea65 100644
> --- a/drivers/net/ethernet/intel/ice/ice_idc.c
> +++ b/drivers/net/ethernet/intel/ice/ice_idc.c
> @@ -34,30 +34,42 @@ ice_get_auxiliary_drv(struct iidc_rdma_core_dev_info
> *cdev)
> * ice_send_event_to_aux - send event to RDMA AUX driver
> * @pf: pointer to PF struct
> * @event: event struct
...
> kfree(event);
> }
> }
> --
> 2.56.0
