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Thu, 9 Jul 2020 00:13:50 +0000 References: <79417f27b7c57da5c0eb54bb6d074d3a472d9ebf.1593209494.git.petrm@mellanox.com> <87a70bic3n.fsf@mellanox.com> <873662i3rc.fsf@mellanox.com> <87wo3dhg63.fsf@mellanox.com> User-agent: mu4e 1.3.3; emacs 26.3 From: Petr Machata To: Cong Wang Cc: Linux Kernel Network Developers , David Miller , Jakub Kicinski , Eric Dumazet , Jiri Pirko , Ido Schimmel Subject: Re: [PATCH net-next v1 2/5] net: sched: Introduce helpers for qevent blocks In-reply-to: <87wo3dhg63.fsf@mellanox.com> Date: Thu, 09 Jul 2020 02:13:47 +0200 Message-ID: <87v9ixh7es.fsf@mellanox.com> Content-Type: text/plain X-ClientProxiedBy: AM0PR07CA0017.eurprd07.prod.outlook.com (2603:10a6:208:ac::30) To HE1PR05MB4746.eurprd05.prod.outlook.com (2603:10a6:7:a3::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from yaviefel (89.176.246.183) by AM0PR07CA0017.eurprd07.prod.outlook.com (2603:10a6:208:ac::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3174.8 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-Network-Message-Id: 06d1f569-207d-437d-b6a9-08d8239cf4c2 X-MS-Exchange-CrossTenant-AuthSource: HE1PR05MB4746.eurprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Jul 2020 00:13:50.3945 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: a652971c-7d2e-4d9b-a6a4-d149256f461b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: vMzc5nRxOc9+4xtNdKwkB2RcXY5v4zTfqLJ+eeZcf7zkK6Rl4ihmfZIr/dBomn8HhggS16cv7B2CaVRaahPFAA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0501MB2171 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Petr Machata writes: > Cong Wang writes: > > I'll think about it some more. For now I will at least fix the lack of > locking. I guess I could store smp_processor_id() that acquired the lock in struct qdisc_skb_head. Do a trylock instead of lock, and on fail check the stored value. I'll need to be careful about the race between unsuccessful trylock and the test, and about making sure CPU ID doesn't change after it is read. I'll probe this tomorrow.