RDMA/core: Fix ordering of CQ pool destruction

rxe will hold a refcount on the IB device as long as CQ objects exist,
this causes destruction of a rxe device to hang if the CQ pool has any
cached CQs since they are being destroyed after the refcount must go to
zero.

Treat the CQ pool like a client and create/destroy it before/after all
other clients. No users of CQ pool can exist past a client remove call.

Link: https://lore.kernel.org/r/e8a240aa-9e9b-3dca-062f-9130b787f29b@acm.org
Fixes: c7ff819a ("RDMA/core: Introduce shared CQ pool API")
Tested-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/core/device.c

@@ -1285,6 +1285,8 @@ static void disable_device(struct ib_device *device)
 		remove_client_context(device, cid);
 	}
 
+	ib_cq_pool_destroy(device);
+
 	/* Pairs with refcount_set in enable_device */
 	ib_device_put(device);
 	wait_for_completion(&device->unreg_completion);
@@ -1328,6 +1330,8 @@ static int enable_device_and_get(struct ib_device *device)
 			goto out;
 	}
 
+	ib_cq_pool_init(device);
+
 	down_read(&clients_rwsem);
 	xa_for_each_marked (&clients, index, client, CLIENT_REGISTERED) {
 		ret = add_client_context(device, client);
@@ -1400,7 +1404,6 @@ int ib_register_device(struct ib_device *device, const char *name)
 		goto dev_cleanup;
 	}
 
-	ib_cq_pool_init(device);
 	ret = enable_device_and_get(device);
 	dev_set_uevent_suppress(&device->dev, false);
 	/* Mark for userspace that device is ready */
@@ -1455,7 +1458,6 @@ static void __ib_unregister_device(struct ib_device *ib_dev)
 		goto out;
 
 	disable_device(ib_dev);
-	ib_cq_pool_destroy(ib_dev);
 
 	/* Expedite removing unregistered pointers from the hash table */
 	free_netdevs(ib_dev);