iw_cxgb4: Fix possible circular dependency locking warning

Locking sequence of iw_cxgb4 and RoCE drivers in ib_register_device() is
slightly different and this leads to possible circular dependency locking
warning when both the devices are brought up.

Here is the locking sequence upto ib_register_device():
iw_cxgb4: rtnl_mutex(net stack) --> uld_mutex --> device_mutex
RoCE drivers: device_mutex --> rtnl_mutex

Here is the possibility of cross locking:

	CPU #0 (iw_cxgb4) 		     CPU #1 (RoCE drivers)

-> on interface up cxgb4_up()
executed with rtnl_mutex held
-> hold uld_mutex and try
registering ib device
					-> In ib_register_device() hold
					   device_mutex
-> hold device mutex in
ib_register_device
					-> try acquiring rtnl_mutex in
					   ib_enum_roce_netdev()

Current patch schedules the ib_register_device() functionality of
iw_cxgb4 to a workqueue to prevent the possible cross-locking.
Also rename the labels in c4iw_reister_device().

Signed-off-by: Potnuri Bharat Teja <bharat@chelsio.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/cxgb4/device.c

@@ -64,14 +64,9 @@ module_param(c4iw_wr_log_size_order, int, 0444);
 MODULE_PARM_DESC(c4iw_wr_log_size_order,
 		 "Number of entries (log2) in the work request timing log.");
 
-struct uld_ctx {
-	struct list_head entry;
-	struct cxgb4_lld_info lldi;
-	struct c4iw_dev *dev;
-};
-
 static LIST_HEAD(uld_ctx_list);
 static DEFINE_MUTEX(dev_mutex);
+struct workqueue_struct *reg_workq;
 
 #define DB_FC_RESUME_SIZE 64
 #define DB_FC_RESUME_DELAY 1
@@ -912,7 +907,7 @@ static void c4iw_rdev_close(struct c4iw_rdev *rdev)
 	c4iw_destroy_resource(&rdev->resource);
 }
 
-static void c4iw_dealloc(struct uld_ctx *ctx)
+void c4iw_dealloc(struct uld_ctx *ctx)
 {
 	c4iw_rdev_close(&ctx->dev->rdev);
 	WARN_ON_ONCE(!idr_is_empty(&ctx->dev->cqidr));
@@ -1208,8 +1203,6 @@ static int c4iw_uld_state_change(void *handle, enum cxgb4_state new_state)
 	case CXGB4_STATE_UP:
 		pr_info("%s: Up\n", pci_name(ctx->lldi.pdev));
 		if (!ctx->dev) {
-			int ret;
-
 			ctx->dev = c4iw_alloc(&ctx->lldi);
 			if (IS_ERR(ctx->dev)) {
 				pr_err("%s: initialization failed: %ld\n",
@@ -1218,12 +1211,9 @@ static int c4iw_uld_state_change(void *handle, enum cxgb4_state new_state)
 				ctx->dev = NULL;
 				break;
 			}
-			ret = c4iw_register_device(ctx->dev);
-			if (ret) {
-				pr_err("%s: RDMA registration failed: %d\n",
-				       pci_name(ctx->lldi.pdev), ret);
-				c4iw_dealloc(ctx);
-			}
+
+			INIT_WORK(&ctx->reg_work, c4iw_register_device);
+			queue_work(reg_workq, &ctx->reg_work);
 		}
 		break;
 	case CXGB4_STATE_DOWN:
@@ -1551,6 +1541,12 @@ static int __init c4iw_init_module(void)
 	if (!c4iw_debugfs_root)
 		pr_warn("could not create debugfs entry, continuing\n");
 
+	reg_workq = create_singlethread_workqueue("Register_iWARP_device");
+	if (!reg_workq) {
+		pr_err("Failed creating workqueue to register iwarp device\n");
+		return -ENOMEM;
+	}
+
 	cxgb4_register_uld(CXGB4_ULD_RDMA, &c4iw_uld_info);
 
 	return 0;
@@ -1567,6 +1563,8 @@ static void __exit c4iw_exit_module(void)
 		kfree(ctx);
 	}
 	mutex_unlock(&dev_mutex);
+	flush_workqueue(reg_workq);
+	destroy_workqueue(reg_workq);
 	cxgb4_unregister_uld(CXGB4_ULD_RDMA);
 	c4iw_cm_term();
 	debugfs_remove_recursive(c4iw_debugfs_root);

drivers/infiniband/hw/cxgb4/iw_cxgb4.h

@@ -322,6 +322,13 @@ struct c4iw_dev {
 	wait_queue_head_t wait;
 };
 
+struct uld_ctx {
+	struct list_head entry;
+	struct cxgb4_lld_info lldi;
+	struct c4iw_dev *dev;
+	struct work_struct reg_work;
+};
+
 static inline struct c4iw_dev *to_c4iw_dev(struct ib_device *ibdev)
 {
 	return container_of(ibdev, struct c4iw_dev, ibdev);
@@ -988,7 +995,7 @@ void c4iw_rqtpool_destroy(struct c4iw_rdev *rdev);
 void c4iw_ocqp_pool_destroy(struct c4iw_rdev *rdev);
 void c4iw_destroy_resource(struct c4iw_resource *rscp);
 int c4iw_destroy_ctrl_qp(struct c4iw_rdev *rdev);
-int c4iw_register_device(struct c4iw_dev *dev);
+void c4iw_register_device(struct work_struct *work);
 void c4iw_unregister_device(struct c4iw_dev *dev);
 int __init c4iw_cm_init(void);
 void c4iw_cm_term(void);
@@ -1014,6 +1021,7 @@ struct ib_mr *c4iw_alloc_mr(struct ib_pd *pd,
 int c4iw_map_mr_sg(struct ib_mr *ibmr, struct scatterlist *sg, int sg_nents,
 		   unsigned int *sg_offset);
 int c4iw_dealloc_mw(struct ib_mw *mw);
+void c4iw_dealloc(struct uld_ctx *ctx);
 struct ib_mw *c4iw_alloc_mw(struct ib_pd *pd, enum ib_mw_type type,
 			    struct ib_udata *udata);
 struct ib_mr *c4iw_reg_user_mr(struct ib_pd *pd, u64 start,

drivers/infiniband/hw/cxgb4/provider.c

@@ -531,10 +531,12 @@ static void get_dev_fw_str(struct ib_device *dev, char *str)
 		 FW_HDR_FW_VER_BUILD_G(c4iw_dev->rdev.lldi.fw_vers));
 }
 
-int c4iw_register_device(struct c4iw_dev *dev)
+void c4iw_register_device(struct work_struct *work)
 {
 	int ret;
 	int i;
+	struct uld_ctx *ctx = container_of(work, struct uld_ctx, reg_work);
+	struct c4iw_dev *dev = ctx->dev;
 
 	pr_debug("c4iw_dev %p\n", dev);
 	strlcpy(dev->ibdev.name, "cxgb4_%d", IB_DEVICE_NAME_MAX);
@@ -609,8 +611,10 @@ int c4iw_register_device(struct c4iw_dev *dev)
 	dev->ibdev.get_dev_fw_str = get_dev_fw_str;
 
 	dev->ibdev.iwcm = kmalloc(sizeof(struct iw_cm_verbs), GFP_KERNEL);
-	if (!dev->ibdev.iwcm)
-		return -ENOMEM;
+	if (!dev->ibdev.iwcm) {
+		ret = -ENOMEM;
+		goto err_dealloc_ctx;
+	}
 
 	dev->ibdev.iwcm->connect = c4iw_connect;
 	dev->ibdev.iwcm->accept = c4iw_accept_cr;
@@ -625,20 +629,24 @@ int c4iw_register_device(struct c4iw_dev *dev)
 
 	ret = ib_register_device(&dev->ibdev, NULL);
 	if (ret)
-		goto bail1;
+		goto err_kfree_iwcm;
 
 	for (i = 0; i < ARRAY_SIZE(c4iw_class_attributes); ++i) {
 		ret = device_create_file(&dev->ibdev.dev,
 					 c4iw_class_attributes[i]);
 		if (ret)
-			goto bail2;
+			goto err_unregister_device;
 	}
-	return 0;
-bail2:
+	return;
+err_unregister_device:
 	ib_unregister_device(&dev->ibdev);
-bail1:
+err_kfree_iwcm:
 	kfree(dev->ibdev.iwcm);
-	return ret;
+err_dealloc_ctx:
+	pr_err("%s - Failed registering iwarp device: %d\n",
+	       pci_name(ctx->lldi.pdev), ret);
+	c4iw_dealloc(ctx);
+	return;
 }
 
 void c4iw_unregister_device(struct c4iw_dev *dev)