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Tue, 14 Jan 2025 16:33:08 +0000 Date: Tue, 14 Jan 2025 17:33:01 +0100 From: Larysa Zaremba To: Tariq Toukan CC: "David S. Miller" , Jakub Kicinski , Paolo Abeni , Eric Dumazet , "Andrew Lunn" , , Saeed Mahameed , Gal Pressman , Leon Romanovsky , Mark Bloch , Moshe Shemesh , Yishai Hadas , Michael Guralnik Subject: Re: [PATCH net 2/8] net/mlx5: Fix a lockdep warning as part of the write combining test Message-ID: References: <20250113154055.1927008-1-tariqt@nvidia.com> <20250113154055.1927008-3-tariqt@nvidia.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250113154055.1927008-3-tariqt@nvidia.com> X-ClientProxiedBy: MI0P293CA0013.ITAP293.PROD.OUTLOOK.COM (2603:10a6:290:44::18) To SN7PR11MB7540.namprd11.prod.outlook.com (2603:10b6:806:340::7) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN7PR11MB7540:EE_|MN2PR11MB4711:EE_ X-MS-Office365-Filtering-Correlation-Id: 25cca318-0539-45f0-5694-08dd34b920b8 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|7416014|7053199007; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?UgAc8BQ7EwZadWPN5NCw4sn/hjdFJ3JE+MKAAYqwfuLsqUGcOBzz9mRJHO35?= =?us-ascii?Q?D8tK8iZr0MBBVybVmPgsufDGU4zVM1AeHz9xEZ7tWkwSiKkgRXnh3D/XG5BT?= =?us-ascii?Q?4BJ7fbz4qrU3faJR1ueqej6Yd7NuVj4LCPZocTINnZvji0l5ze8X0y5QxAd1?= =?us-ascii?Q?KayUTRvMR1NqP+y/a0KZHoaijRlnZOz3vMjpOhHOs4TmoDRs1e4FHaInNdKx?= =?us-ascii?Q?mhTE3JWsRKzFjT9CNlpkZugPYTx0nDTeIWfoolxt2Zc4OYcgTDAvn7dZByKp?= =?us-ascii?Q?yAG9G9OoTpFiunUzV0ZdCEhdGr5AcdLSCw69xegejTuj2Em15tK7hQjbgcO4?= =?us-ascii?Q?BPFHLe0CIzBZ6AbH8sRs1xQmArOdJdrrxBYir3V+8P+bbZm7Qbi9vIcnqOGv?= =?us-ascii?Q?f4dzG93DLwyg2bw1fNXErjectp2UHOexboy1b1/KBsFWizz+d7WzdJKT2Slh?= =?us-ascii?Q?kq12c2b9YWsqnQHP35atW7X8JxZRWOkZZB+xF0MZTxzh7gpNaEioD043A9/b?= =?us-ascii?Q?pz2PnsmVphaZM9WxTTnkAlQItv7dT49xoRB5lqPUz5jBds85ubrxvUTob+nW?= =?us-ascii?Q?VAIYZvuuqyxdRhqmR5lKRm4Gg4m8Ud01+Gpn40kHiP6gzRV2FTSHDQf1Au6g?= =?us-ascii?Q?ePQ6g8lPgc5Xv4Jjp7/aHYgDhUr+Zg0xC26IsIofU3uEIljIquzW8YafTuDa?= =?us-ascii?Q?KrVzS1hfErtmZgYRuMtE6KJXj3wiFoubhDLraso84QwMzn/fuhTWIqJ+l61I?= =?us-ascii?Q?k8wAsoHzWc3j0TneQjlvmdxDhn8CR04/StA6GbeIE1fjtcIomAjhaEAw2amM?= =?us-ascii?Q?wxqg+rEMrMHxPcH45IAdmZaxMrkWvSHxtNE526mK6lvj4Z/E5E3W2+ihKzjp?= =?us-ascii?Q?ZvWcFmZevxc7oUlQqGl5rJbFDNoddhG8cFzEr6DxyEsv1+OcpuRBvr8Q8nNL?= =?us-ascii?Q?yb+/IU8F7snEb6CMY5sl3U7Y3ycopnvERInI4Gtk/Mexi4Zk6ekw5u/KoJQB?= =?us-ascii?Q?gIy0oGI2ADNp9tqk2j+5Ibs+LKj0SQO9Ovj2p368UjhB8rDa2A7+rjKuabnl?= =?us-ascii?Q?JoWVagjwUPqUQegPBLUgPTF24gZuYZw/8EMhjRWJLtxqpjVlEc6Qy5DK+6ym?= =?us-ascii?Q?Vq0CiSA+dQAcQqB3q1MA8STYq+isFLEu3PHiR05e45b781piffZVkm/H7QR9?= =?us-ascii?Q?LGNZagQM/1a3N9DFMgj0f70oI3mb7zSt4IP2qvryuGQtyscrQQ1FZr50KJaH?= =?us-ascii?Q?HX75XvmmQ+ycz4RQ2gCh+EboHxf7+XAtwMaLEwZ9uqo+UguzszW/wq+kq8r/?= =?us-ascii?Q?vpkI/qyNvYB6kAjqXod4XzdptDwfgXsr5XBcKroc74QQZcnPfwg2dYiPOuO+?= =?us-ascii?Q?n8TfVBhdeeAdVDPutmqKOYqQDwbucJGUkSv7LC2IFWLr3FpkmPKX3D7u6jah?= =?us-ascii?Q?KA9RYXDjEevAyIRUbdAw/y1JvddGI5PhUGP1ifSRzrZIgW+g980HTLZNM0H/?= =?us-ascii?Q?sxBeEA31rXyOguFbbSOAUSd7gtYpEx6HuhkAsUoGE9nK1p7Rolus5BGPFQQA?= =?us-ascii?Q?5u5xQZ1kCAnaUOQR7BGEyAlNugG81lKM9cj8p9yfwwOywbUWMtg82+Sbo28q?= =?us-ascii?Q?Mg=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 25cca318-0539-45f0-5694-08dd34b920b8 X-MS-Exchange-CrossTenant-AuthSource: SN7PR11MB7540.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Jan 2025 16:33:08.0358 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: F14DnfPFcNaYFoARwztB9emPJF2B59kI/zwKaJLz7r3xlvqFImd9z57BGJbT8U1eyNUfPKpAPKNA7Riwvb/vpsobezpuhWXIaj7pq/AKuWU= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR11MB4711 X-OriginatorOrg: intel.com On Mon, Jan 13, 2025 at 05:40:48PM +0200, Tariq Toukan wrote: > From: Yishai Hadas > > Fix a lockdep warning [1] observed during the write combining test. > > The warning indicates a potential nested lock scenario that could lead > to a deadlock. > > However, this is a false positive alarm because the SF lock and its > parent lock are distinct ones. > > The lockdep confusion arises because the locks belong to the same object > class (i.e., struct mlx5_core_dev). > > To resolve this, the code has been refactored to avoid taking both > locks. Instead, only the parent lock is acquired. > [...] > > Fixes: d98995b4bf98 ("net/mlx5: Reimplement write combining test") > Signed-off-by: Yishai Hadas > Reviewed-by: Michael Guralnik > Signed-off-by: Tariq Toukan Reviewed-by: Larysa Zaremba > --- > drivers/net/ethernet/mellanox/mlx5/core/wc.c | 24 ++++++++++---------- > 1 file changed, 12 insertions(+), 12 deletions(-) > > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/wc.c b/drivers/net/ethernet/mellanox/mlx5/core/wc.c > index 1bed75eca97d..740b719e7072 100644 > --- a/drivers/net/ethernet/mellanox/mlx5/core/wc.c > +++ b/drivers/net/ethernet/mellanox/mlx5/core/wc.c > @@ -382,6 +382,7 @@ static void mlx5_core_test_wc(struct mlx5_core_dev *mdev) > > bool mlx5_wc_support_get(struct mlx5_core_dev *mdev) > { > + struct mutex *wc_state_lock = &mdev->wc_state_lock; > struct mlx5_core_dev *parent = NULL; > > if (!MLX5_CAP_GEN(mdev, bf)) { > @@ -400,32 +401,31 @@ bool mlx5_wc_support_get(struct mlx5_core_dev *mdev) > */ > goto out; > > - mutex_lock(&mdev->wc_state_lock); > - > - if (mdev->wc_state != MLX5_WC_STATE_UNINITIALIZED) > - goto unlock; > - > #ifdef CONFIG_MLX5_SF > - if (mlx5_core_is_sf(mdev)) > + if (mlx5_core_is_sf(mdev)) { > parent = mdev->priv.parent_mdev; > + wc_state_lock = &parent->wc_state_lock; > + } > #endif > > - if (parent) { > - mutex_lock(&parent->wc_state_lock); > + mutex_lock(wc_state_lock); > > + if (mdev->wc_state != MLX5_WC_STATE_UNINITIALIZED) > + goto unlock; > + > + if (parent) { > mlx5_core_test_wc(parent); > > mlx5_core_dbg(mdev, "parent set wc_state=%d\n", > parent->wc_state); > mdev->wc_state = parent->wc_state; > > - mutex_unlock(&parent->wc_state_lock); > + } else { > + mlx5_core_test_wc(mdev); > } > > - mlx5_core_test_wc(mdev); > - > unlock: > - mutex_unlock(&mdev->wc_state_lock); > + mutex_unlock(wc_state_lock); > out: > mlx5_core_dbg(mdev, "wc_state=%d\n", mdev->wc_state); > > -- > 2.45.0 > >