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Mon, 22 Jun 2020 12:57:33 +0000 Subject: Re: [PATCH rdma-next 2/2] RDMA/core: Optimize XRC target lookup To: Jason Gunthorpe , Leon Romanovsky Cc: Doug Ledford , linux-rdma@vger.kernel.org References: <20200621104110.53509-1-leon@kernel.org> <20200621104110.53509-3-leon@kernel.org> <20200622122910.GB2590509@mellanox.com> From: Maor Gottlieb Message-ID: <3ee325e8-6872-22a8-4f2b-e1740d15a194@mellanox.com> Date: Mon, 22 Jun 2020 15:57:29 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.1 In-Reply-To: <20200622122910.GB2590509@mellanox.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-ClientProxiedBy: FR2P281CA0014.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:a::24) To AM0PR05MB5873.eurprd05.prod.outlook.com (2603:10a6:208:125::25) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [10.100.102.11] (93.173.18.107) by FR2P281CA0014.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:a::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3109.22 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: 20bc0802-d825-4a0f-eb1e-08d816abd49d X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Jun 2020 12:57:33.6812 (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: bJ5Kz6JUGFQZdxNuiPybAFWpXFy01Fu9uk3M6bP54UrDZ5/3R76jr0pKhUQJSUusw3UIACuZV+bExmc3zoMKCg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM0PR05MB4321 Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 6/22/2020 3:29 PM, Jason Gunthorpe wrote: > On Sun, Jun 21, 2020 at 01:41:10PM +0300, Leon Romanovsky wrote: >> @@ -2318,19 +2313,18 @@ EXPORT_SYMBOL(ib_alloc_xrcd_user); >> >> int ib_dealloc_xrcd_user(struct ib_xrcd *xrcd, struct ib_udata *udata) >> { >> + unsigned long index; >> struct ib_qp *qp; >> int ret; >> >> if (atomic_read(&xrcd->usecnt)) >> return -EBUSY; >> >> - while (!list_empty(&xrcd->tgt_qp_list)) { >> - qp = list_entry(xrcd->tgt_qp_list.next, struct ib_qp, xrcd_list); >> + xa_for_each(&xrcd->tgt_qps, index, qp) { >> ret = ib_destroy_qp(qp); >> if (ret) >> return ret; >> } > Why doesn't this need to hold the tgt_qps_rwsem? > > Jason Actually, we don't need this part of code. if usecnt is zero so we don't have any tgt qp in the list. I guess it is leftovers of ib_release_qp which was already deleted.