[PATCH net V2] net/mlx5e: TC, Check if flow is PEER before acquiring devcom lock
From: Tariq Toukan
Date: Tue Jul 28 2026 - 00:45:11 EST
From: Shay Drory <shayd@xxxxxxxxxx>
In case __mlx5e_add_fdb_flow() fails in lower levels, the flow is
deleted via mlx5e_tc_del_flow(), and mlx5e_tc_del_flow() is acquiring
ESW devcom lock without condition. In addition, in case of peer_flow,
__mlx5e_add_fdb_flow() is called while holding ESW devcom comp lock.
This results in an AA deadlock.
To fix this, introduce a new PEER flag that is set on flows created as
peer flows (the duplicate flows on peer devices), and check it in
mlx5e_tc_del_flow() before acquiring ESW devcom lock.
Lockdep splat:
============================================
WARNING: possible recursive locking detected
============================================
Possible unsafe locking scenario:
CPU0
----
lock(&comp->lock_key#2);
lock(&comp->lock_key#2);
*** DEADLOCK ***
Call Trace:
<TASK>
dump_stack_lvl+0x69/0xa0
print_deadlock_bug.cold+0xbd/0xca
__lock_acquire+0x1671/0x2ec0
lock_acquire+0x10e/0x2e0
down_read+0x95/0x430
mlx5_devcom_for_each_peer_begin+0x4e/0xe0 [mlx5_core]
mlx5e_tc_del_flow+0x11d/0xa70 [mlx5_core]
mlx5e_flow_put+0x99/0x100 [mlx5_core]
__mlx5e_add_fdb_flow+0x409/0xf00 [mlx5_core]
mlx5e_configure_flower+0x2a86/0x4100 [mlx5_core]
mlx5e_rep_setup_tc_cls_flower+0x12f/0x1b0 [mlx5_core]
mlx5e_rep_setup_tc_cb+0x153/0x750 [mlx5_core]
tc_setup_cb_add+0x1dc/0x470
fl_change+0x2f4d/0x626d [cls_flower]
tc_new_tfilter+0x79b/0x2310
rtnetlink_rcv_msg+0x778/0xad0
do_syscall_64+0x70/0x960
entry_SYSCALL_64_after_hwframe+0x4b/0x53
</TASK>
Fixes: 04de7dda7394 ("net/mlx5e: Infrastructure for duplicated offloading of TC flows")
Signed-off-by: Shay Drory <shayd@xxxxxxxxxx>
Reviewed-by: Cosmin Ratiu <cratiu@xxxxxxxxxx>
Signed-off-by: Tariq Toukan <tariqt@xxxxxxxxxx>
---
drivers/net/ethernet/mellanox/mlx5/core/en/tc_priv.h | 1 +
drivers/net/ethernet/mellanox/mlx5/core/en_tc.c | 4 +++-
2 files changed, 4 insertions(+), 1 deletion(-)
V2: Remove leftover pharagraph from commit message.
V1: https://patchwork.kernel.org/project/netdevbpf/patch/20260717073041.1241894-1-tariqt@xxxxxxxxxx/
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/tc_priv.h b/drivers/net/ethernet/mellanox/mlx5/core/en/tc_priv.h
index 28cab4bf525c..7bfe7cdc5770 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/tc_priv.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/tc_priv.h
@@ -30,6 +30,7 @@ enum {
MLX5E_TC_FLOW_FLAG_FAILED = MLX5E_TC_FLOW_BASE + 9,
MLX5E_TC_FLOW_FLAG_SAMPLE = MLX5E_TC_FLOW_BASE + 10,
MLX5E_TC_FLOW_FLAG_USE_ACT_STATS = MLX5E_TC_FLOW_BASE + 11,
+ MLX5E_TC_FLOW_FLAG_PEER = MLX5E_TC_FLOW_BASE + 12,
};
struct mlx5e_tc_flow_parse_attr {
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
index 1bc7b9019124..b290beb4369a 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
@@ -2161,7 +2161,8 @@ static void mlx5e_tc_del_flow(struct mlx5e_priv *priv,
if (mlx5e_is_eswitch_flow(flow)) {
struct mlx5_devcom_comp_dev *devcom = flow->priv->mdev->priv.eswitch->devcom;
- if (!mlx5_devcom_for_each_peer_begin(devcom)) {
+ if (flow_flag_test(flow, PEER) ||
+ !mlx5_devcom_for_each_peer_begin(devcom)) {
mlx5e_tc_del_fdb_flow(priv, flow);
return;
}
@@ -4628,6 +4629,7 @@ static int mlx5e_tc_add_fdb_peer_flow(struct flow_cls_offload *f,
else
in_mdev = priv->mdev;
+ flow_flags |= BIT(MLX5E_TC_FLOW_FLAG_PEER);
parse_attr = flow->attr->parse_attr;
peer_flow = __mlx5e_add_fdb_flow(peer_priv, f, flow_flags,
parse_attr->filter_dev,
base-commit: 97ac08560d236ca17f6606d9e671118e5eae5721
--
2.44.0