net/mlx5: Lag, avoid lockdep warnings

ldev->lock is used to serialize lag change operations. Since multiport
eswtich functionality was added, we now change the mode dynamically.
However, acquiring ldev->lock is not allowed as it could possibly lead
to a deadlock as reported by the lockdep mechanism.

[  836.154963] WARNING: possible circular locking dependency detected
[  836.155850] 5.19.0-rc5_net_56b7df2 #1 Not tainted
[  836.156549] ------------------------------------------------------
[  836.157418] handler1/12198 is trying to acquire lock:
[  836.158178] ffff888187d52b58 (&ldev->lock){+.+.}-{3:3}, at: mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core]
[  836.159575]
[  836.159575] but task is already holding lock:
[  836.160474] ffff8881d4de2930 (&block->cb_lock){++++}-{3:3}, at: tc_setup_cb_add+0x5b/0x200
[  836.161669] which lock already depends on the new lock.
[  836.162905]
[  836.162905] the existing dependency chain (in reverse order) is:
[  836.164008] -> #3 (&block->cb_lock){++++}-{3:3}:
[  836.164946]        down_write+0x25/0x60
[  836.165548]        tcf_block_get_ext+0x1c6/0x5d0
[  836.166253]        ingress_init+0x74/0xa0 [sch_ingress]
[  836.167028]        qdisc_create.constprop.0+0x130/0x5e0
[  836.167805]        tc_modify_qdisc+0x481/0x9f0
[  836.168490]        rtnetlink_rcv_msg+0x16e/0x5a0
[  836.169189]        netlink_rcv_skb+0x4e/0xf0
[  836.169861]        netlink_unicast+0x190/0x250
[  836.170543]        netlink_sendmsg+0x243/0x4b0
[  836.171226]        sock_sendmsg+0x33/0x40
[  836.171860]        ____sys_sendmsg+0x1d1/0x1f0
[  836.172535]        ___sys_sendmsg+0xab/0xf0
[  836.173183]        __sys_sendmsg+0x51/0x90
[  836.173836]        do_syscall_64+0x3d/0x90
[  836.174471]        entry_SYSCALL_64_after_hwframe+0x46/0xb0
[  836.175282]

[  836.175282] -> #2 (rtnl_mutex){+.+.}-{3:3}:
[  836.176190]        __mutex_lock+0x6b/0xf80
[  836.176830]        register_netdevice_notifier+0x21/0x120
[  836.177631]        rtnetlink_init+0x2d/0x1e9
[  836.178289]        netlink_proto_init+0x163/0x179
[  836.178994]        do_one_initcall+0x63/0x300
[  836.179672]        kernel_init_freeable+0x2cb/0x31b
[  836.180403]        kernel_init+0x17/0x140
[  836.181035]        ret_from_fork+0x1f/0x30

 [  836.181687] -> #1 (pernet_ops_rwsem){+.+.}-{3:3}:
[  836.182628]        down_write+0x25/0x60
[  836.183235]        unregister_netdevice_notifier+0x1c/0xb0
[  836.184029]        mlx5_ib_roce_cleanup+0x94/0x120 [mlx5_ib]
[  836.184855]        __mlx5_ib_remove+0x35/0x60 [mlx5_ib]
[  836.185637]        mlx5_eswitch_unregister_vport_reps+0x22f/0x440 [mlx5_core]
[  836.186698]        auxiliary_bus_remove+0x18/0x30
[  836.187409]        device_release_driver_internal+0x1f6/0x270
[  836.188253]        bus_remove_device+0xef/0x160
[  836.188939]        device_del+0x18b/0x3f0
[  836.189562]        mlx5_rescan_drivers_locked+0xd6/0x2d0 [mlx5_core]
[  836.190516]        mlx5_lag_remove_devices+0x69/0xe0 [mlx5_core]
[  836.191414]        mlx5_do_bond_work+0x441/0x620 [mlx5_core]
[  836.192278]        process_one_work+0x25c/0x590
[  836.192963]        worker_thread+0x4f/0x3d0
[  836.193609]        kthread+0xcb/0xf0
[  836.194189]        ret_from_fork+0x1f/0x30

[  836.194826] -> #0 (&ldev->lock){+.+.}-{3:3}:
[  836.195734]        __lock_acquire+0x15b8/0x2a10
[  836.196426]        lock_acquire+0xce/0x2d0
[  836.197057]        __mutex_lock+0x6b/0xf80
[  836.197708]        mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core]
[  836.198575]        tc_act_parse_mirred+0x25b/0x800 [mlx5_core]
[  836.199467]        parse_tc_actions+0x168/0x5a0 [mlx5_core]
[  836.200340]        __mlx5e_add_fdb_flow+0x263/0x480 [mlx5_core]
[  836.201241]        mlx5e_configure_flower+0x8a0/0x1820 [mlx5_core]
[  836.202187]        tc_setup_cb_add+0xd7/0x200
[  836.202856]        fl_hw_replace_filter+0x14c/0x1f0 [cls_flower]
[  836.203739]        fl_change+0xbbe/0x1730 [cls_flower]
[  836.204501]        tc_new_tfilter+0x407/0xd90
[  836.205168]        rtnetlink_rcv_msg+0x406/0x5a0
[  836.205877]        netlink_rcv_skb+0x4e/0xf0
[  836.206535]        netlink_unicast+0x190/0x250
[  836.207217]        netlink_sendmsg+0x243/0x4b0
[  836.207915]        sock_sendmsg+0x33/0x40
[  836.208538]        ____sys_sendmsg+0x1d1/0x1f0
[  836.209219]        ___sys_sendmsg+0xab/0xf0
[  836.209878]        __sys_sendmsg+0x51/0x90
[  836.210510]        do_syscall_64+0x3d/0x90
[  836.211137]        entry_SYSCALL_64_after_hwframe+0x46/0xb0

[  836.211954] other info that might help us debug this:
[  836.213174] Chain exists of:
[  836.213174]   &ldev->lock --> rtnl_mutex --> &block->cb_lock
   836.214650]  Possible unsafe locking scenario:
[  836.214650]
[  836.215574]        CPU0                    CPU1
[  836.216255]        ----                    ----
[  836.216943]   lock(&block->cb_lock);
[  836.217518]                                lock(rtnl_mutex);
[  836.218348]                                lock(&block->cb_lock);
[  836.219212]   lock(&ldev->lock);
[  836.219758]
[  836.219758]  *** DEADLOCK ***
[  836.219758]
 [  836.220747] 2 locks held by handler1/12198:
[  836.221390]  #0: ffff8881d4de2930 (&block->cb_lock){++++}-{3:3}, at: tc_setup_cb_add+0x5b/0x200
[  836.222646]  #1: ffff88810c9a92c0 (&esw->mode_lock){++++}-{3:3}, at: mlx5_esw_hold+0x39/0x50 [mlx5_core]

[  836.224063] stack backtrace:
[  836.224799] CPU: 6 PID: 12198 Comm: handler1 Not tainted 5.19.0-rc5_net_56b7df2 #1
[  836.225923] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[  836.227476] Call Trace:
[  836.227929]  <TASK>
[  836.228332]  dump_stack_lvl+0x57/0x7d
[  836.228924]  check_noncircular+0x104/0x120
[  836.229562]  __lock_acquire+0x15b8/0x2a10
[  836.230201]  lock_acquire+0xce/0x2d0
[  836.230776]  ? mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core]
[  836.231614]  ? find_held_lock+0x2b/0x80
[  836.232221]  __mutex_lock+0x6b/0xf80
[  836.232799]  ? mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core]
[  836.233636]  ? mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core]
[  836.234451]  ? xa_load+0xc3/0x190
[  836.234995]  mlx5_lag_do_mirred+0x3b/0x70 [mlx5_core]
[  836.235803]  tc_act_parse_mirred+0x25b/0x800 [mlx5_core]
[  836.236636]  ? tc_act_can_offload_mirred+0x135/0x210 [mlx5_core]
[  836.237550]  parse_tc_actions+0x168/0x5a0 [mlx5_core]
[  836.238364]  __mlx5e_add_fdb_flow+0x263/0x480 [mlx5_core]
[  836.239202]  mlx5e_configure_flower+0x8a0/0x1820 [mlx5_core]
[  836.240076]  ? lock_acquire+0xce/0x2d0
[  836.240668]  ? tc_setup_cb_add+0x5b/0x200
[  836.241294]  tc_setup_cb_add+0xd7/0x200
[  836.241917]  fl_hw_replace_filter+0x14c/0x1f0 [cls_flower]
[  836.242709]  fl_change+0xbbe/0x1730 [cls_flower]
[  836.243408]  tc_new_tfilter+0x407/0xd90
[  836.244043]  ? tc_del_tfilter+0x880/0x880
[  836.244672]  rtnetlink_rcv_msg+0x406/0x5a0
[  836.245310]  ? netlink_deliver_tap+0x7a/0x4b0
[  836.245991]  ? if_nlmsg_stats_size+0x2b0/0x2b0
[  836.246675]  netlink_rcv_skb+0x4e/0xf0
[  836.258046]  netlink_unicast+0x190/0x250
[  836.258669]  netlink_sendmsg+0x243/0x4b0
[  836.259288]  sock_sendmsg+0x33/0x40
[  836.259857]  ____sys_sendmsg+0x1d1/0x1f0
[  836.260473]  ___sys_sendmsg+0xab/0xf0
[  836.261064]  ? lock_acquire+0xce/0x2d0
[  836.261669]  ? find_held_lock+0x2b/0x80
[  836.262272]  ? __fget_files+0xb9/0x190
[  836.262871]  ? __fget_files+0xd3/0x190
[  836.263462]  __sys_sendmsg+0x51/0x90
[  836.264064]  do_syscall_64+0x3d/0x90
[  836.264652]  entry_SYSCALL_64_after_hwframe+0x46/0xb0
[  836.265425] RIP: 0033:0x7fdbe5e2677d

[  836.266012] Code: 28 89 54 24 1c 48 89 74 24 10 89 7c 24 08 e8 ba ee
ff ff 8b 54 24 1c 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 2e 00 00 00 0f
05 <48> 3d 00 f0 ff ff 77 33 44 89 c7 48 89 44 24 08 e8 ee ee ff ff 48
[  836.268485] RSP: 002b:00007fdbe48a75a0 EFLAGS: 00000293 ORIG_RAX: 000000000000002e
[  836.269598] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fdbe5e2677d
[  836.270576] RDX: 0000000000000000 RSI: 00007fdbe48a7640 RDI: 000000000000003c
[  836.271565] RBP: 00007fdbe48a8368 R08: 0000000000000000 R09: 0000000000000000
[  836.272546] R10: 00007fdbe48a84b0 R11: 0000000000000293 R12: 0000557bd17dc860
[  836.273527] R13: 0000000000000000 R14: 0000557bd17dc860 R15: 00007fdbe48a7640

[  836.274521]  </TASK>

To avoid using mode holding ldev->lock in the configure flow, we queue a
work to the lag workqueue and cease wait on a completion object.

In addition, we remove the lock from mlx5_lag_do_mirred() since it is
not really protecting anything.

It should be noted that an actual deadlock has not been observed.

Signed-off-by: Eli Cohen <[email protected]>
Reviewed-by: Mark Bloch <[email protected]>
Signed-off-by: Saeed Mahameed <[email protected]>

Author: elic307i

drivers/net/ethernet/mellanox/mlx5/core/lag/lag.c

@@ -228,9 +228,8 @@ static void mlx5_ldev_free(struct kref *ref)
 	if (ldev->nb.notifier_call)
 		unregister_netdevice_notifier_net(&init_net, &ldev->nb);
 	mlx5_lag_mp_cleanup(ldev);
-	mlx5_lag_mpesw_cleanup(ldev);
-	cancel_work_sync(&ldev->mpesw_work);
 	destroy_workqueue(ldev->wq);
+	mlx5_lag_mpesw_cleanup(ldev);
 	mutex_destroy(&ldev->lock);
 	kfree(ldev);
 }

drivers/net/ethernet/mellanox/mlx5/core/lag/lag.h

@@ -50,6 +50,19 @@ struct lag_tracker {
 	enum netdev_lag_hash hash_type;
 };
 
+enum mpesw_op {
+	MLX5_MPESW_OP_ENABLE,
+	MLX5_MPESW_OP_DISABLE,
+};
+
+struct mlx5_mpesw_work_st {
+	struct work_struct work;
+	struct mlx5_lag    *lag;
+	enum mpesw_op	   op;
+	struct completion  comp;
+	int result;
+};
+
 /* LAG data of a ConnectX card.
  * It serves both its phys functions.
  */
@@ -66,7 +79,6 @@ struct mlx5_lag {
 	struct lag_tracker        tracker;
 	struct workqueue_struct   *wq;
 	struct delayed_work       bond_work;
-	struct work_struct	  mpesw_work;
 	struct notifier_block     nb;
 	struct lag_mp             lag_mp;
 	struct mlx5_lag_port_sel  port_sel;

drivers/net/ethernet/mellanox/mlx5/core/lag/mpesw.c

@@ -7,76 +7,105 @@
 #include "eswitch.h"
 #include "lib/mlx5.h"
 
-void mlx5_mpesw_work(struct work_struct *work)
+static int add_mpesw_rule(struct mlx5_lag *ldev)
 {
-	struct mlx5_lag *ldev = container_of(work, struct mlx5_lag, mpesw_work);
+	struct mlx5_core_dev *dev = ldev->pf[MLX5_LAG_P1].dev;
+	int err;
 
-	mutex_lock(&ldev->lock);
-	mlx5_disable_lag(ldev);
-	mutex_unlock(&ldev->lock);
-}
+	if (atomic_add_return(1, &ldev->lag_mpesw.mpesw_rule_count) != 1)
+		return 0;
 
-static void mlx5_lag_disable_mpesw(struct mlx5_core_dev *dev)
-{
-	struct mlx5_lag *ldev = dev->priv.lag;
+	if (ldev->mode != MLX5_LAG_MODE_NONE) {
+		err = -EINVAL;
+		goto out_err;
+	}
 
-	if (!queue_work(ldev->wq, &ldev->mpesw_work))
-		mlx5_core_warn(dev, "failed to queue work\n");
+	err = mlx5_activate_lag(ldev, NULL, MLX5_LAG_MODE_MPESW, false);
+	if (err) {
+		mlx5_core_warn(dev, "Failed to create LAG in MPESW mode (%d)\n", err);
+		goto out_err;
+	}
+
+	return 0;
+
+out_err:
+	atomic_dec(&ldev->lag_mpesw.mpesw_rule_count);
+	return err;
 }
 
-void mlx5_lag_del_mpesw_rule(struct mlx5_core_dev *dev)
+static void del_mpesw_rule(struct mlx5_lag *ldev)
 {
-	struct mlx5_lag *ldev = dev->priv.lag;
+	if (!atomic_dec_return(&ldev->lag_mpesw.mpesw_rule_count) &&
+	    ldev->mode == MLX5_LAG_MODE_MPESW)
+		mlx5_disable_lag(ldev);
+}
 
-	if (!ldev)
-		return;
+static void mlx5_mpesw_work(struct work_struct *work)
+{
+	struct mlx5_mpesw_work_st *mpesww = container_of(work, struct mlx5_mpesw_work_st, work);
+	struct mlx5_lag *ldev = mpesww->lag;
 
 	mutex_lock(&ldev->lock);
-	if (!atomic_dec_return(&ldev->lag_mpesw.mpesw_rule_count) &&
-	    ldev->mode == MLX5_LAG_MODE_MPESW)
-		mlx5_lag_disable_mpesw(dev);
+	if (mpesww->op == MLX5_MPESW_OP_ENABLE)
+		mpesww->result = add_mpesw_rule(ldev);
+	else if (mpesww->op == MLX5_MPESW_OP_DISABLE)
+		del_mpesw_rule(ldev);
 	mutex_unlock(&ldev->lock);
+
+	complete(&mpesww->comp);
 }
 
-int mlx5_lag_add_mpesw_rule(struct mlx5_core_dev *dev)
+static int mlx5_lag_mpesw_queue_work(struct mlx5_core_dev *dev,
+				     enum mpesw_op op)
 {
 	struct mlx5_lag *ldev = dev->priv.lag;
+	struct mlx5_mpesw_work_st *work;
 	int err = 0;
 
 	if (!ldev)
 		return 0;
 
-	mutex_lock(&ldev->lock);
-	if (atomic_add_return(1, &ldev->lag_mpesw.mpesw_rule_count) != 1)
-		goto out;
+	work = kzalloc(sizeof(*work), GFP_KERNEL);
+	if (!work)
+		return -ENOMEM;
 
-	if (ldev->mode != MLX5_LAG_MODE_NONE) {
+	INIT_WORK(&work->work, mlx5_mpesw_work);
+	init_completion(&work->comp);
+	work->op = op;
+	work->lag = ldev;
+
+	if (!queue_work(ldev->wq, &work->work)) {
+		mlx5_core_warn(dev, "failed to queue mpesw work\n");
 		err = -EINVAL;
 		goto out;
 	}
-
-	err = mlx5_activate_lag(ldev, NULL, MLX5_LAG_MODE_MPESW, false);
-	if (err)
-		mlx5_core_warn(dev, "Failed to create LAG in MPESW mode (%d)\n", err);
-
+	wait_for_completion(&work->comp);
+	err = work->result;
 out:
-	mutex_unlock(&ldev->lock);
+	kfree(work);
 	return err;
 }
 
+void mlx5_lag_del_mpesw_rule(struct mlx5_core_dev *dev)
+{
+	mlx5_lag_mpesw_queue_work(dev, MLX5_MPESW_OP_DISABLE);
+}
+
+int mlx5_lag_add_mpesw_rule(struct mlx5_core_dev *dev)
+{
+	return mlx5_lag_mpesw_queue_work(dev, MLX5_MPESW_OP_ENABLE);
+}
+
 int mlx5_lag_do_mirred(struct mlx5_core_dev *mdev, struct net_device *out_dev)
 {
 	struct mlx5_lag *ldev = mdev->priv.lag;
 
 	if (!netif_is_bond_master(out_dev) || !ldev)
 		return 0;
 
-	mutex_lock(&ldev->lock);
-	if (ldev->mode == MLX5_LAG_MODE_MPESW) {
-		mutex_unlock(&ldev->lock);
+	if (ldev->mode == MLX5_LAG_MODE_MPESW)
 		return -EOPNOTSUPP;
-	}
-	mutex_unlock(&ldev->lock);
+
 	return 0;
 }
 
@@ -90,11 +119,10 @@ bool mlx5_lag_mpesw_is_activated(struct mlx5_core_dev *dev)
 
 void mlx5_lag_mpesw_init(struct mlx5_lag *ldev)
 {
-	INIT_WORK(&ldev->mpesw_work, mlx5_mpesw_work);
 	atomic_set(&ldev->lag_mpesw.mpesw_rule_count, 0);
 }
 
 void mlx5_lag_mpesw_cleanup(struct mlx5_lag *ldev)
 {
-	cancel_delayed_work_sync(&ldev->bond_work);
+	WARN_ON(atomic_read(&ldev->lag_mpesw.mpesw_rule_count));
 }

drivers/net/ethernet/mellanox/mlx5/core/lag/mpesw.h

@@ -12,7 +12,6 @@ struct lag_mpesw {
 	atomic_t mpesw_rule_count;
 };
 
-void mlx5_mpesw_work(struct work_struct *work);
 int mlx5_lag_do_mirred(struct mlx5_core_dev *mdev, struct net_device *out_dev);
 bool mlx5_lag_mpesw_is_activated(struct mlx5_core_dev *dev);
 #if IS_ENABLED(CONFIG_MLX5_ESWITCH)