RDMA/mlx5: Fix UMR hang in LAG error state unload

RDMA/mlx5: Fix UMR hang in LAG error state unload

During firmware reset in LAG mode, a race condition causes the driver
to hang indefinitely while waiting for UMR completion during device
unload. See [1].

In LAG mode the bond device is only registered on the master, so it
never sees sys_error events from the slave.
During firmware reset this causes UMR waits to hang forever on unload
as the slave is dead but the master hasn't entered error state yet, so
UMR posts succeed but completions never arrive.

Fix this by adding a sys_error notifier that gets registered before
MLX5_IB_STAGE_IB_REG and stays alive until after ib_unregister_device().
This ensures error events reach the bond device throughout teardown.

[1]
Call Trace:
 __schedule+0x2bd/0x760
 schedule+0x37/0xa0
 schedule_preempt_disabled+0xa/0x10
 __mutex_lock.isra.6+0x2b5/0x4a0
 __mlx5_ib_dereg_mr+0x606/0x870 [mlx5_ib]
 ? __xa_erase+0x4a/0xa0
 ? _cond_resched+0x15/0x30
 ? wait_for_completion+0x31/0x100
 ib_dereg_mr_user+0x48/0xc0 [ib_core]
 ? rdmacg_uncharge_hierarchy+0xa0/0x100
 destroy_hw_idr_uobject+0x20/0x50 [ib_uverbs]
 uverbs_destroy_uobject+0x37/0x150 [ib_uverbs]
 __uverbs_cleanup_ufile+0xda/0x140 [ib_uverbs]
 uverbs_destroy_ufile_hw+0x3a/0xf0 [ib_uverbs]
 ib_uverbs_remove_one+0xc3/0x140 [ib_uverbs]
 remove_client_context+0x8b/0xd0 [ib_core]
 disable_device+0x8c/0x130 [ib_core]
 __ib_unregister_device+0x10d/0x180 [ib_core]
 ib_unregister_device+0x21/0x30 [ib_core]
 __mlx5_ib_remove+0x1e4/0x1f0 [mlx5_ib]
 auxiliary_bus_remove+0x1e/0x30
 device_release_driver_internal+0x103/0x1f0
 bus_remove_device+0xf7/0x170
 device_del+0x181/0x410
 mlx5_rescan_drivers_locked.part.10+0xa9/0x1d0 [mlx5_core]
 mlx5_disable_lag+0x253/0x260 [mlx5_core]
 mlx5_lag_disable_change+0x89/0xc0 [mlx5_core]
 mlx5_eswitch_disable+0x67/0xa0 [mlx5_core]
 mlx5_unload+0x15/0xd0 [mlx5_core]
 mlx5_unload_one+0x71/0xc0 [mlx5_core]
 mlx5_sync_reset_reload_work+0x83/0x100 [mlx5_core]
 process_one_work+0x1a7/0x360
 worker_thread+0x30/0x390
 ? create_worker+0x1a0/0x1a0
 kthread+0x116/0x130
 ? kthread_flush_work_fn+0x10/0x10
 ret_from_fork+0x22/0x40

Fixes: ede132a5cf55 ("RDMA/mlx5: Move events notifier registration to be after device registration")
Signed-off-by: Chiara Meiohas <cmeiohas@nvidia.com>
Signed-off-by: Maher Sanalla <msanalla@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://patch.msgid.link/20260113-umr-hand-lag-fix-v1-1-3dc476e00cd9@nvidia.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>