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Thu, 2 Sep 2021 09:37:24 +0000 Date: Thu, 2 Sep 2021 12:37:07 +0300 From: Dan Carpenter To: Sagi Grimberg Cc: sagi@lightbitslabs.com, linux-nvme@lists.infradead.org Subject: Re: [bug report] nvme-tcp: add NVMe over TCP host driver Message-ID: <20210902093707.GC2129@kadam> References: <20210824131638.GA5558@kili> Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-ClientProxiedBy: JNXP275CA0021.ZAFP275.PROD.OUTLOOK.COM (2603:1086:0:19::33) To MWHPR1001MB2365.namprd10.prod.outlook.com (2603:10b6:301:2d::28) MIME-Version: 1.0 Received: from kadam (62.8.83.99) by JNXP275CA0021.ZAFP275.PROD.OUTLOOK.COM (2603:1086:0:19::33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4478.17 via Frontend Transport; Thu, 2 Sep 2021 09:37:21 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: c68d2fc4-5df4-45ee-b704-08d96df544e2 X-MS-TrafficTypeDiagnostic: CO1PR10MB4690: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:7691; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Wed, Sep 01, 2021 at 05:56:55PM +0300, Sagi Grimberg wrote: > > > On 8/24/21 4:16 PM, Dan Carpenter wrote: > > Hello Sagi Grimberg, > > > > The patch 3f2304f8c6d6: "nvme-tcp: add NVMe over TCP host driver" > > from Dec 3, 2018, leads to the following > > Smatch static checker warning: > > > > drivers/nvme/host/multipath.c:101 nvme_kick_requeue_lists() > > warn: sleeping in atomic context > > > > drivers/nvme/host/multipath.c > > 97 void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl) > > 98 { > > 99 struct nvme_ns *ns; > > 100 > > --> 101 down_read(&ctrl->namespaces_rwsem); > > 102 list_for_each_entry(ns, &ctrl->namespaces, list) { > > 103 if (ns->head->disk) > > 104 kblockd_schedule_work(&ns->head->requeue_work); > > 105 } > > 106 up_read(&ctrl->namespaces_rwsem); > > 107 } > > > > This is a new Smatch warning I'm working on and it's sort of > > overwhelming because it has generates too many warnings and they're > > complicated to analyze and report. I'm trying to send these > > automatically generated call trees to see if it will help. > > > > nvme_fc_unregister_remoteport() <- disables preempt > > -> nvme_fc_ctrl_connectivity_loss() > > -> nvme_reset_ctrl() > > nvme_fc_ctrl_connectivity_loss() > > nvme_fc_unregister_remoteport() <- disables preempt > > nvme_fc_exit_module() <- disables preempt > > -> nvme_fc_cleanup_for_unload() > > -> nvme_fc_delete_controllers() <- disables preempt > > -> nvme_delete_ctrl() > > nvme_tcp_state_change() <- disables preempt > > -> nvme_tcp_error_recovery() > > -> nvme_change_ctrl_state() > > -> nvme_kick_requeue_lists() > > > > > > I looked at the last call tree and it seems like potentially a real bug. > > > > nvme_tcp_state_change() <- disables preempt > > -> nvme_tcp_error_recovery() > > -> nvme_change_ctrl_state() > > -> nvme_kick_requeue_lists() > > That is a correct analysis. However from this flow, it is impossible to > step into the condition that triggers nvme_kick_requeue_lists because we > call nvme_change_ctrl_state with state NVME_CTRL_RESETTING from > nvme_tcp_error_recovery which means that the new state cannot be > NVME_CTRL_LIVE as the state will either transition to the desired state or > fail and be unchanged. > > I wander what action should we take here? make the effort to defer the > call to a workqueue context? or we can safely ignore it? Yeah. Just ignore it. Later versions of Smatch might be clever enough to figure this out. regards, dan carpenter _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme