2020-12-08 20:59:08

by Vladimir Oltean

Subject: [PATCH rdma-next] RDMA/mlx4: remove bogus dev_base_lock usage

It is not clear what this lock protects. If the authors wanted to ensure
that "dev" does not disappear, that is impossible, given the following
code path:

mlx4_ib_netdev_event (under RTNL mutex)
-> mlx4_ib_scan_netdevs
-> mlx4_ib_update_qps

Also, the dev_base_lock does not protect dev->dev_addr either.

So it serves no purpose here. Remove it.

Reviewed-by: Leon Romanovsky <[email protected]>
Signed-off-by: Vladimir Oltean <[email protected]>
---
drivers/infiniband/hw/mlx4/main.c | 3 ---
1 file changed, 3 deletions(-)

diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
index f0864f40ea1a..e3cd402c079a 100644
--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -2265,10 +2265,7 @@ static void mlx4_ib_update_qps(struct mlx4_ib_dev *ibdev,
u64 release_mac = MLX4_IB_INVALID_MAC;
struct mlx4_ib_qp *qp;

- read_lock(&dev_base_lock);
new_smac = mlx4_mac_to_u64(dev->dev_addr);
- read_unlock(&dev_base_lock);
-
atomic64_set(&ibdev->iboe.mac[port - 1], new_smac);

/* no need for update QP1 and mac registration in non-SRIOV */
--
2.25.1

2020-12-10 21:11:42

by Jason Gunthorpe

Subject: Re: [PATCH rdma-next] RDMA/mlx4: remove bogus dev_base_lock usage

On Tue, Dec 08, 2020 at 09:39:28PM +0200, Vladimir Oltean wrote:
> It is not clear what this lock protects. If the authors wanted to ensure
> that "dev" does not disappear, that is impossible, given the following
> code path:
>
> mlx4_ib_netdev_event (under RTNL mutex)
> -> mlx4_ib_scan_netdevs
> -> mlx4_ib_update_qps
>
> Also, the dev_base_lock does not protect dev->dev_addr either.
>
> So it serves no purpose here. Remove it.
>
> Reviewed-by: Leon Romanovsky <[email protected]>
> Signed-off-by: Vladimir Oltean <[email protected]>
> ---
> drivers/infiniband/hw/mlx4/main.c | 3 ---
> 1 file changed, 3 deletions(-)

Applied to for-next, thanks

Jason