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[91.78.208.152]) by smtp.googlemail.com with ESMTPSA id b28sm1638162ljp.90.2020.04.01.09.04.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Apr 2020 09:04:39 -0700 (PDT) Subject: Re: [PATCH v10 54/55] Input: atmel_mxt_ts: Implement synchronization during various operation To: Jiada Wang , nick@shmanahar.org, dmitry.torokhov@gmail.com, jikos@kernel.org, benjamin.tissoires@redhat.com, bsz@semihalf.com Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, erosca@de.adit-jv.com, Andrew_Gabbasov@mentor.com References: <20200331105051.58896-1-jiada_wang@mentor.com> <20200331105051.58896-55-jiada_wang@mentor.com> From: Dmitry Osipenko Message-ID: Date: Wed, 1 Apr 2020 19:04:38 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200331105051.58896-55-jiada_wang@mentor.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 31.03.2020 13:50, Jiada Wang пишет: > From: Sanjeev Chugh > > There could be scope of race conditions when sysfs is being handled > and at the same time, device removal is occurring. For example, > we don't want the device removal to begin if the Atmel device > cfg update is going on or firmware update is going on. In such > cases, wait for device update to be completed before the removal > continues. > > Thread Thread 2: > ========================= ========================= > mxt_update_fw_store() mxt_remove() > mutex_lock(&data->lock) ... > mxt_initialize() //Tries to acquire lock > request_firmware_nowait() mutex_lock(&data->lock) > ... ==>waits for lock() > ... . > ... . > mutex_unlock(&data->lock) . > //Gets lock and proceeds > mxt_free_input_device(); > ... > mutex_unlock(&data->lock) > //Frees atmel driver data > kfree(data) > > If the request_firmware_nowait() completes after the driver removal, > and callback is triggered. But kernel crashes since the module is > already removed. > > This commit adds state machine to serialize such scenarios. Won't it be easier to bump driver's module use-count by __module_get() while firmware is updating? Or remove sysfs during of mxt_remove()?