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Thu, 16 Jul 2020 11:48:27 +0000 Subject: Re: [PATCH v3] watchdog: initialize device before misc_register To: "krzysztof.sobota@nokia.com" , Guenter Roeck , wim@linux-watchdog.org, linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org References: <55fa2e05-9a99-b205-2dad-b797786af22a@nokia.com> <1f20e45d-aba5-6226-27f2-cb6438cc224e@nokia.com> From: Alexander Sverdlin Message-ID: Date: Thu, 16 Jul 2020 13:48:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <1f20e45d-aba5-6226-27f2-cb6438cc224e@nokia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MA1PR01CA0077.INDPRD01.PROD.OUTLOOK.COM (2603:1096:a00::17) To HE1PR07MB4412.eurprd07.prod.outlook.com (2603:10a6:7:96::13) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from ulegcpsvhp1.emea.nsn-net.net (131.228.32.167) by MA1PR01CA0077.INDPRD01.PROD.OUTLOOK.COM (2603:1096:a00::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3195.17 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: Yu/t/XkmvEYRMaOyOahw83veoMM6mX/QtS6HbuYaTQ2/rTb2INFSZjVcDSjmPDgjpUtddSX5nm+SI/XtO9K55BGiIsH6rxmJvz9tX7GCOU3vqApeDHkUH9UJXdJhK7ZPfN8ulUFGY8U0K9DI2aaEUYtLoVlVrPXUsWBqmYOQMmM5dCZt6enE4NgemAeZeA5Ipwf+RF5lmJK7JkUHVwpDKYMxRb9koXQ9qR4N9oKm1ITGuJI/93VVDAQohTYClcSNbNaQWqP00EgcKEmLJ/TPc0ysiLMYwed0wvW/FunVwudyIWRr+RFN3eJpgdM6isMASeSdHgAy5JATvatrR82Vx1lEdV2+xQoyCSuT89TLhMiiSOWmH5T2XxzB+w0sQYZ8jwliE57yBzmD38EBYwC/4r1sHJyvWEaO8QZiGipklH+m0rDAQEx95eg5k1ndO1dwrEpwryd+jnxL+8vLgqA6LfYKw6nUDUZbHuePGGw4KTVUzlAz4u4DvOrCEt2Iib2a X-OriginatorOrg: nokia.com X-MS-Exchange-CrossTenant-Network-Message-Id: e00a56e2-ad29-40e7-1f78-08d8297e26d0 X-MS-Exchange-CrossTenant-AuthSource: HE1PR07MB4412.eurprd07.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jul 2020 11:48:27.1494 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 5d471751-9675-428d-917b-70f44f9630b0 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 5hAtsjWb5UjwLCYkUadrlU5zHnYXcsKU2pSVKZQ2IT6JODJy9wCydYfP/kZSibeTkNI53qyOHJKDrbwJKi+w1mpMhp4dCAv3PfUqGLHRQf0= X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0701MB2764 Sender: linux-watchdog-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org Hello Krzysztof, On 16/07/2020 13:32, krzysztof.sobota@nokia.com wrote: > When watchdog device is being registered, it calls misc_register that > makes watchdog available for systemd to open. This is a data race > scenario, because when device is open it may still have device struct > not initialized - this in turn causes a crash. This patch moves > device initialization before misc_register call and it solves the > problem printed below. [...] thank you for looking into this! > Fixes: 72139dfa2464 ("watchdog: Fix the race between the release of watchdog_core_data and cdev") > Reviewed-by: Guenter Roeck Reviewed-by: Alexander Sverdlin > Signed-off-by: Krzysztof Sobota > --- > v1 -> v2: > * removed Change-Id tag > * added Review-by tag > v2 -> v3 > * convert spaces to tabs > * convert (hopefully) mail to plaintext > --- > drivers/watchdog/watchdog_dev.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c > index 10b2090f3e5e..1c322caecf7f 100644 > --- a/drivers/watchdog/watchdog_dev.c > +++ b/drivers/watchdog/watchdog_dev.c > @@ -947,6 +947,15 @@ static int watchdog_cdev_register(struct watchdog_device *wdd) > if (IS_ERR_OR_NULL(watchdog_kworker)) > return -ENODEV; > > + device_initialize(&wd_data->dev); > + wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id); > + wd_data->dev.class = &watchdog_class; > + wd_data->dev.parent = wdd->parent; > + wd_data->dev.groups = wdd->groups; > + wd_data->dev.release = watchdog_core_data_release; > + dev_set_drvdata(&wd_data->dev, wdd); > + dev_set_name(&wd_data->dev, "watchdog%d", wdd->id); > + > kthread_init_work(&wd_data->work, watchdog_ping_work); > hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); > wd_data->timer.function = watchdog_timer_expired; > @@ -967,15 +976,6 @@ static int watchdog_cdev_register(struct watchdog_device *wdd) > } > } > > - device_initialize(&wd_data->dev); > - wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id); > - wd_data->dev.class = &watchdog_class; > - wd_data->dev.parent = wdd->parent; > - wd_data->dev.groups = wdd->groups; > - wd_data->dev.release = watchdog_core_data_release; > - dev_set_drvdata(&wd_data->dev, wdd); > - dev_set_name(&wd_data->dev, "watchdog%d", wdd->id); > - > /* Fill in the data structures */ > cdev_init(&wd_data->cdev, &watchdog_fops); > > -- > 2.14.0 > -- Best regards, Alexander Sverdlin.