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Miller" , Greg Kroah-Hartman , Oliver Neukum Cc: linux-usb@vger.kernel.org, netdev@vger.kernel.org References: <20220501175828.8185-1-ryazanov.s.a@gmail.com> From: Oliver Neukum In-Reply-To: <20220501175828.8185-1-ryazanov.s.a@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AM5PR1001CA0035.EURPRD10.PROD.OUTLOOK.COM (2603:10a6:206:2::48) To VI1PR0401MB2526.eurprd04.prod.outlook.com (2603:10a6:800:58::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: f9402458-517b-4c19-45ef-08da2c26cee1 X-MS-TrafficTypeDiagnostic: PAXPR04MB9374:EE_ X-LD-Processed: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba,ExtFwd X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VI1PR0401MB2526.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230001)(366004)(316002)(8936002)(38100700002)(508600001)(6486002)(31696002)(86362001)(6666004)(53546011)(6506007)(6512007)(110136005)(2906002)(36756003)(66574015)(66476007)(66556008)(8676002)(31686004)(66946007)(4326008)(186003)(2616005)(83380400001)(5660300002)(43740500002)(45980500001);DIR:OUT;SFP:1101; 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As soon as last user closes the cdc-wdm device file, the > driver cancels any ongoing requests, resets the pending response > counter, but leaves the response reading in-progress flag > (WDM_RESPONDING) untouched. > > So if the user closes the device file during the response receive > request is being performed, no more data will be obtained from the > modem. The request will be cancelled, effectively preventing the > WDM_RESPONDING flag from being reseted. Keeping the flag set will > prevent a new response receive request from being sent, permanently > blocking the read path. The read path will staying blocked until the > module will be reloaded or till the modem will be re-attached. > > This stuck has been observed with a Huawei E3372 modem attached to an > OpenWrt router and using the comgt utility to set up a network > connection. > > Fix this issue by clearing the WDM_RESPONDING flag on the device file > close. > > Without this fix, the device reading stuck can be easily reproduced in a > few connection establishing attempts. With this fix, a load test for > modem connection re-establishing worked for several hours without any > issues. > > Fixes: 922a5eadd5a3 ("usb: cdc-wdm: Fix race between autosuspend and > reading from the device") > Signed-off-by: Sergey Ryazanov > Acked-by: Oliver Neukum