[PATCH AUTOSEL 4.19 133/671] net/mlx5: Take lock with IRQs disabled to avoid deadlock

Sasha Levin
2020-01-16T19:11:22Z

From: Moni Shoua <monis@mellanox.com>

[ Upstream commit 33814e5d127e21f53b52e17b0722c1b57d4f4d29 ]

The lock in qp_table might be taken from process context or from
interrupt context. This may lead to a deadlock unless it is taken with
IRQs disabled.

Discovered by lockdep

================================
WARNING: inconsistent lock state
4.20.0-rc6
--------------------------------
inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W}

python/12572 [HC1[1]:SC0[0]:HE0:SE1] takes:
00000000052a4df4 (&(&table->lock)->rlock#2){?.+.}, /0x50 [mlx5_core]
{HARDIRQ-ON-W} state was registered at:
_raw_spin_lock+0x33/0x70
mlx5_get_rsc+0x1a/0x50 [mlx5_core]
mlx5_ib_eqe_pf_action+0x493/0x1be0 [mlx5_ib]
process_one_work+0x90c/0x1820
worker_thread+0x87/0xbb0
kthread+0x320/0x3e0
ret_from_fork+0x24/0x30
irq event stamp: 103928
hardirqs last enabled at (103927): [] nk+0x1a/0x1c
hardirqs last disabled at (103928): [] unk+0x1a/0x1c
softirqs last enabled at (103924): [] tcp_sendmsg+0x31/0x40
softirqs last disabled at (103922): [] 80

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&(&table->lock)->rlock#2);

lock(&(&table->lock)->rlock#2);

*** DEADLOCK ***

Fixes: 032080ab43ac ("IB/mlx5: Lock QP during page fault handling")
Signed-off-by: Moni Shoua <monis@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/mellanox/mlx5/core/qp.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/qp.c b/drivers/net/ethernet/mellanox/mlx5/core/qp.c
index f33707ce8b6b..479ac21cdbc6 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/qp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/qp.c
@@ -44,14 +44,15 @@ static struct mlx5_core_rsc_common *mlx5_get_rsc(struct mlx5_core_dev *dev,
{
struct mlx5_qp_table *table = &dev->priv.qp_table;
struct mlx5_core_rsc_common *common;
+ unsigned long flags;

- spin_lock(&table->lock);
+ spin_lock_irqsave(&table->lock, flags);

common = radix_tree_lookup(&table->tree, rsn);
if (common)
atomic_inc(&common->refcount);

- spin_unlock(&table->lock);
+ spin_unlock_irqrestore(&table->lock, flags);

if (!common) {
mlx5_core_warn(dev, "Async event for bogus resource 0x%x\n",
--
2.20.1