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charset=UTF-8 Content-Transfer-Encoding: 7bit On 01/02/2024 08:29, Christoph Winklhofer wrote: >>> + >>> +static void w1_uart_remove(struct serdev_device *serdev) >>> +{ >>> + struct w1_uart_device *w1dev = serdev_device_get_drvdata(serdev); >>> + >>> + mutex_lock(&w1dev->mutex); >>> + >>> + w1_remove_master_device(&w1dev->bus); >>> + >>> + mutex_unlock(&w1dev->mutex); >> >> This is still suspicious. You do not have serdev_device_close and you >> want to protect from concurrent access but it looks insufficient. >> >> This code assumes that: >> >> w1_uart_remove() >> <-- here concurrent read/write might start >> mutex_lock() >> w1_remove_master_device() >> mutex_unlock() >> <-- now w1_uart_serdev_tx_rx() or w1_uart_serdev_receive_buf() can be >> executed, but device is removed. So what's the point of the mutex here? >> >> What exactly is protected by the mutex? So far it looks like only some >> contents of w1dev, but it does not matter, because it that memory is >> still valid at this point. >> >> After describing what is protected we can think whether it is really >> protected... >> >> >>> >> >> Best regards, >> Krzysztof >> > > Yes, it is still suspicious, sorry.. > > After w1_uart_remove, serdev is closed and w1dev is released. Therefore > the w1-callback (w1_uart_serdev_tx_rx) must be finished before returning I did not even go to end of w1_uart_remove(). In my code above, that thread is still in w1_uart_remove(), just after unlocking mutex. > from w1_uart_remove. That was the intention with the lock and trylock. Then it does not look really protected. To be honest, w1-gpio and other drivers also might have a race here. You can test it by adding long sleeps in read/write paths and then trying to unbind device. Maybe this should be fixed everywhere, but this mutex here brings more questions. Best regards, Krzysztof