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Thu, 12 Feb 2026 02:32:57 -0800 From: Tariq Toukan To: Eric Dumazet , Jakub Kicinski , Paolo Abeni , Andrew Lunn , "David S. Miller" CC: Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Mark Bloch , , , , Gal Pressman , Moshe Shemesh , Jianbo Liu Subject: [PATCH net 2/6] net/mlx5: Fix misidentification of write combining CQE during poll loop Date: Thu, 12 Feb 2026 12:32:13 +0200 Message-ID: <20260212103217.1752943-3-tariqt@nvidia.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20260212103217.1752943-1-tariqt@nvidia.com> References: <20260212103217.1752943-1-tariqt@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY4PEPF0000EE37:EE_|IA1PR12MB6018:EE_ X-MS-Office365-Filtering-Correlation-Id: 0ef2ba0b-1ab0-488b-c767-08de6a2221dc X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|82310400026|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?fe88+JyhI/fWw10CnvHy9SZ94aKK4ieEUcXCcgG52zV24htYB8nJDPfikHVo?= =?us-ascii?Q?JhqB239pVt79+zv99dHW1hJ36t9nUQJprIq5sh3WjSl8gEucbBUabHUsd8fo?= =?us-ascii?Q?Vx3zvE66uqW4uF/BrkVvArBbSzlgX1iUXwgjzLgn6j7L9brSFBLASEN//kGD?= =?us-ascii?Q?A+FIR+ZCGPJvcYCggQJ+wa6nJQWc5maS3mZByKihguzp/g8DXgURYjHMyxQO?= =?us-ascii?Q?D9BnKSZT5DdW+vwJS3fka3nV08J6b2FU46neTf5b70XMKnQ8A7rIwn1Lqexy?= =?us-ascii?Q?T9x8NOOaz9wvZ0yo85BTnSPwNCls1j8Dh/Asi+Xq2gmpgIrH2u8zJ61OZgrM?= =?us-ascii?Q?rfHqwGhLN3ZTQuZDdrM3OQjq5Fba3SiOljhpjHCqJ6eZC81YOn/Woc+nKMox?= =?us-ascii?Q?3DVLsI00zcMxGkcTk/P5h72Y0d0C1n9Ux7j0Khc0eJPqp7dQ4AfqmLuPe86j?= =?us-ascii?Q?ieMtLM7MFTwGa5HchIaFuCyFxP9p1rurFnnUVyCMpPW/jtHIz3XKof9eH3tV?= =?us-ascii?Q?gFSIAE69TugkBvVMUNQusDDP3VPt2PRUo8jAlHnTlGL4m9p/wmJXKMmcJfVO?= =?us-ascii?Q?rk+lbG1v7XcHTjFpU2dfOeWfooPlcXKQ6KY15rklUwTQpfU6fFACXsFxEJYo?= =?us-ascii?Q?40wZK24gMw5zrgWcF+wTqhWhul9EdBJqMK6PnkUN6ISfF67JmcWh43JNBmsZ?= =?us-ascii?Q?mVFPs4LElMmuNBU4hw8aotHkTQfMRh2tFoGhBtcnNOpKUp9HLDSpa9rDJCCk?= =?us-ascii?Q?EXVlwSptC7lGn8Y2mR5CCTteNREX/9bknxzs8o42Z7VLVJCPVIuvVCk3etRq?= =?us-ascii?Q?9f9IF72Ol2wtLKb9WRGd048H0ML8QfYw5YmN69Afyl9p1wPOC8aolzpQkq79?= =?us-ascii?Q?EzLIiJlnOEM8MINvjQC64vgGl5vzDKS13FuBfxLG9A9KzkI6MEUWrp7zmRZK?= =?us-ascii?Q?aHLM3o5Lmmy/73IOnvSTvJFLbJb2cD92dPYwwfhuSlKIa1vvAN0nrq++lbkg?= =?us-ascii?Q?wz5fsgJh9DNHTDAq/PY4+eD9SdQf4pc78XBQwsmqs9SM2o06EYCbqtI+6Eph?= =?us-ascii?Q?XJXJYSa/KcCiZKOEuvAWpEea9LB+5j88Wmh60hYcR5n9JH3SOCdx9R+ujLGe?= =?us-ascii?Q?qPnHJmmgmmmmzDifWDpWuKDj1S7eyfz0ACW8mbKteBDyIaNBgDVWQpa2KUup?= =?us-ascii?Q?MzJJCtojgWn2CJ/l+lNDfVLinMfpzm+YCTwRxv+QKjXhjJomFaOsyQSHz8wu?= =?us-ascii?Q?7H507xMo4NOaYieR9cRoDz5fR4iOtpF+KUBBQ1MWOvpCJd4xBD6GrkT8FBeX?= =?us-ascii?Q?2Cy39KxMfuEgl7j+IUmH3bdpKTSipqVqq87HkCZs7XOGes7ly2aJUzK0bRVc?= =?us-ascii?Q?FlhGBpuq5lBAqy0tCzJJ48Kbwfl81A26A6hRu6cWWnG4IPFidEDtiisAo02/?= =?us-ascii?Q?KZkxGCibjcemBLS7VsJUDZ85/Y4390xhAbsjKhUafXoX/zgI7uti6e4uNsot?= =?us-ascii?Q?XPrIj5MDsZpND2XU+olCp4U4iJwB1x7JaCqCsHyPzRd9TP5XC99ZoA0D89EF?= =?us-ascii?Q?EtGqCFqbXmr9zPZzzF4S0UWMWZ9cuZO15Jonyt3DkREgkkp4Gd9YWc+Rl62K?= =?us-ascii?Q?y2qnAg+E1FZdAVPFP8rr+ZDgedU3zkSwKkxPL9Pl3S+a7UkNXb3pl34zVAOh?= =?us-ascii?Q?Tt2VHQ=3D=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(1800799024)(376014)(82310400026)(36860700013);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: E4MY2jNHXrx2rb5wkjFWw+d2mZUPLy8xgwC7Ns4GjRs2LhRTB8qxb6yMxGJjQcJasY+4HEpxrKx8KG42Ucz6q8k8z+R2laF+Z/3UbNOXYfzFFfCycxW81M3lx6RS2IO56h6vUuk+NYALrIgBGyWQ/oQWWTqMitew9mpiqkGSD4bU2uyy9HTALjBp/n1529LaAOjtNoR8z0AcEAx3HMq8nSL+0RhUaeKcknWgXn2dX3kdRbT957fLDTV2NEkYADXokQzRKTPJGj0GYPScXC9Xt9r3pTi0NY/qSI2+JdFSZhFuYVWEBXz0Qdorr/2k6O3uUP3GXOAETZuG/wKQE/vcqd01OW4vWttpXXnoI9scKxFv3TTrLTJ84k857whtd1I9qRiZyt/iEvqeX4m+LrYYAGVJI7aH+NY43OTPy39TBMRcO5rb7nGQXevu8Ji3Bmds X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Feb 2026 10:33:16.1287 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0ef2ba0b-1ab0-488b-c767-08de6a2221dc X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CY4PEPF0000EE37.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB6018 Content-Type: text/plain; charset="utf-8" From: Gal Pressman The write combining completion poll loop uses usleep_range() which can sleep much longer than requested due to scheduler latency. Under load, we witnessed a 20ms+ delay until the process was rescheduled, causing the jiffies based timeout to expire while the thread is sleeping. The original do-while loop structure (poll, sleep, check timeout) would exit without a final poll when waking after timeout, missing a CQE that arrived during sleep. Restructure the loop by moving the poll into the while condition, ensuring we always poll after sleeping, catching CQEs that arrived during that time. While at it, remove the redundant 'err' assignment. Fixes: d98995b4bf98 ("net/mlx5: Reimplement write combining test") Signed-off-by: Gal Pressman Reviewed-by: Jianbo Liu Signed-off-by: Tariq Toukan --- drivers/net/ethernet/mellanox/mlx5/core/wc.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/wc.c b/drivers/net/eth= ernet/mellanox/mlx5/core/wc.c index 815a7c97d6b0..29db15c4b978 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/wc.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/wc.c @@ -390,12 +390,10 @@ static void mlx5_core_test_wc(struct mlx5_core_dev *m= dev) mlx5_wc_post_nop(sq, &offset, true); =20 expires =3D jiffies + TEST_WC_POLLING_MAX_TIME_JIFFIES; - do { - err =3D mlx5_wc_poll_cq(sq); - if (err) - usleep_range(2, 10); - } while (mdev->wc_state =3D=3D MLX5_WC_STATE_UNINITIALIZED && - time_is_after_jiffies(expires)); + while ((mlx5_wc_poll_cq(sq), + mdev->wc_state =3D=3D MLX5_WC_STATE_UNINITIALIZED) && + time_is_after_jiffies(expires)) + usleep_range(2, 10); =20 mlx5_wc_destroy_sq(sq); =20 --=20 2.44.0