Subject: [PATCH 26/33] net/mlx5e: Fix possible deadlock of VXLAN lock

From: Gal Pressman <[email-masked]>
Date: Thu, 23 Nov 2017 13:52:28 +0200

[ Upstream commit 6323514116404cc651df1b7fffa1311ddf8ce647 ]

mlx5e_vxlan_lookup_port is called both from mlx5e_add_vxlan_port (user
context) and mlx5e_features_check (softirq), but the lock acquired does
not disable bottom half and might result in deadlock. Fix it by simply
replacing spin_lock() with spin_lock_bh().
While at it, replace all unnecessary spin_lock_irq() to spin_lock_bh().

lockdep's WARNING: inconsistent lock state
[  654.028136] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[  654.028229] swapper/5/0 [HC0[0]:SC1[9]:HE1:SE0] takes:
[  654.028321]  (&(&vxlan_db->lock)->rlock){+.?.}, at: [<ffffffffa06e7f0e>] mlx5e_vxlan_lookup_port+0x1e/0x50 [mlx5_core]
[  654.028528] {SOFTIRQ-ON-W} state was registered at:
[  654.028607]   _raw_spin_lock+0x3c/0x70
[  654.028689]   mlx5e_vxlan_lookup_port+0x1e/0x50 [mlx5_core]
[  654.028794]   mlx5e_vxlan_add_port+0x2e/0x120 [mlx5_core]
[  654.028878]   process_one_work+0x1e9/0x640
[  654.028942]   worker_thread+0x4a/0x3f0
[  654.029002]   kthread+0x141/0x180
[  654.029056]   ret_from_fork+0x24/0x30
[  654.029114] irq event stamp: 579088
[  654.029174] hardirqs last  enabled at (579088): [<ffffffff818f475a>] ip6_finish_output2+0x49a/0x8c0
[  654.029309] hardirqs last disabled at (579087): [<ffffffff818f470e>] ip6_finish_output2+0x44e/0x8c0
[  654.029446] softirqs last  enabled at (579030): [<ffffffff810b3b3d>] irq_enter+0x6d/0x80
[  654.029567] softirqs last disabled at (579031): [<ffffffff810b3c05>] irq_exit+0xb5/0xc0
[  654.029684] other info that might help us debug this:
[  654.029781]  Possible unsafe locking scenario:

[  654.029868]        CPU0
[  654.029908]        ----
[  654.029947]   lock(&(&vxlan_db->lock)->rlock);
[  654.030045]   <Interrupt>
[  654.030090]     lock(&(&vxlan_db->lock)->rlock);
[  654.030162]
 *** DEADLOCK ***

Fixes: b3f63c3d5e2c ("net/mlx5e: Add netdev support for VXLAN tunneling")
Signed-off-by: Gal Pressman <[email-masked]>
Signed-off-by: Saeed Mahameed <[email-masked]>
---
 drivers/net/ethernet/mellanox/mlx5/core/vxlan.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/vxlan.c b/drivers/net/ethernet/mellanox/mlx5/core/vxlan.c
index 07a9ba6..f823827 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/vxlan.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/vxlan.c
@@ -71,9 +71,9 @@ struct mlx5e_vxlan *mlx5e_vxlan_lookup_port(struct mlx5e_priv *priv, u16 port)
 	struct mlx5e_vxlan_db *vxlan_db = &priv->vxlan;
 	struct mlx5e_vxlan *vxlan;
 
-	spin_lock(&vxlan_db->lock);
+	spin_lock_bh(&vxlan_db->lock);
 	vxlan = radix_tree_lookup(&vxlan_db->tree, port);
-	spin_unlock(&vxlan_db->lock);
+	spin_unlock_bh(&vxlan_db->lock);
 
 	return vxlan;
 }
@@ -100,9 +100,9 @@ static void mlx5e_vxlan_add_port(struct work_struct *work)
 
 	vxlan->udp_port = port;
 
-	spin_lock_irq(&vxlan_db->lock);
+	spin_lock_bh(&vxlan_db->lock);
 	err = radix_tree_insert(&vxlan_db->tree, vxlan->udp_port, vxlan);
-	spin_unlock_irq(&vxlan_db->lock);
+	spin_unlock_bh(&vxlan_db->lock);
 	if (err)
 		goto err_free;
 
@@ -121,9 +121,9 @@ static void __mlx5e_vxlan_core_del_port(struct mlx5e_priv *priv, u16 port)
 	struct mlx5e_vxlan_db *vxlan_db = &priv->vxlan;
 	struct mlx5e_vxlan *vxlan;
 
-	spin_lock_irq(&vxlan_db->lock);
+	spin_lock_bh(&vxlan_db->lock);
 	vxlan = radix_tree_delete(&vxlan_db->tree, port);
-	spin_unlock_irq(&vxlan_db->lock);
+	spin_unlock_bh(&vxlan_db->lock);
 
 	if (!vxlan)
 		return;
@@ -171,12 +171,12 @@ void mlx5e_vxlan_cleanup(struct mlx5e_priv *priv)
 	struct mlx5e_vxlan *vxlan;
 	unsigned int port = 0;
 
-	spin_lock_irq(&vxlan_db->lock);
+	spin_lock_bh(&vxlan_db->lock);
 	while (radix_tree_gang_lookup(&vxlan_db->tree, (void **)&vxlan, port, 1)) {
 		port = vxlan->udp_port;
-		spin_unlock_irq(&vxlan_db->lock);
+		spin_unlock_bh(&vxlan_db->lock);
 		__mlx5e_vxlan_core_del_port(priv, (u16)port);
-		spin_lock_irq(&vxlan_db->lock);
+		spin_lock_bh(&vxlan_db->lock);
 	}
-	spin_unlock_irq(&vxlan_db->lock);
+	spin_unlock_bh(&vxlan_db->lock);
 }
-- 
2.9.5