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[217.229.171.160]) by smtp.gmail.com with ESMTPSA id p12sm6516578wrt.20.2021.06.04.05.47.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Jun 2021 05:47:16 -0700 (PDT) Subject: Re: [PATCH 4/7] platform/surface: aggregator_cdev: Add support for forwarding events to user-space To: Hans de Goede Cc: Mark Gross , Jonathan Corbet , platform-driver-x86@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210603234526.2503590-1-luzmaximilian@gmail.com> <20210603234526.2503590-5-luzmaximilian@gmail.com> From: Maximilian Luz Message-ID: <778047e2-2b1d-ef8b-4fe3-aafba8fa2dba@gmail.com> Date: Fri, 4 Jun 2021 14:47:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/4/21 1:32 PM, Hans de Goede wrote: > Hi, > > I've one review remark inline below. > > On 6/4/21 1:45 AM, Maximilian Luz wrote: [...] >> +static int ssam_cdev_device_open(struct inode *inode, struct file *filp) >> +{ >> + struct miscdevice *mdev = filp->private_data; >> + struct ssam_cdev_client *client; >> + struct ssam_cdev *cdev = container_of(mdev, struct ssam_cdev, mdev); >> + >> + /* Initialize client */ >> + client = vzalloc(sizeof(*client)); >> + if (!client) >> + return -ENOMEM; >> + >> + client->cdev = ssam_cdev_get(cdev); >> + >> + INIT_LIST_HEAD(&client->node); >> + >> + mutex_init(&client->notifier_lock); >> + >> + mutex_init(&client->read_lock); >> + mutex_init(&client->write_lock); >> + INIT_KFIFO(client->buffer); >> + init_waitqueue_head(&client->waitq); >> + >> + filp->private_data = client; >> + >> + /* Attach client. */ >> + down_write(&cdev->client_lock); >> + >> + if (test_bit(SSAM_CDEV_DEVICE_SHUTDOWN_BIT, &cdev->flags)) { >> + up_write(&cdev->client_lock); >> + ssam_cdev_put(client->cdev); > > You are missing the mutex_destroy() calls here which you are > doing in ssam_cdev_device_release(). Thank you for noticing this! This code is based on Surface DTX code which has the same problem, I'll send in a fix for that shortly. > Or maybe move the mutex_init calls below this check > (before the up_write()) since I don't think the client can > be accessed by any code until the up_write is done? Yes, that would also be possible, but I'd prefer adding the mutex_destroy() calls in the failure path. To me that seems a bit easier to reason about. Thanks, Max