Consider the following events involving drivers/tty/serial/owl-uart.c: Suppose the driver is registered, and the owl_uart_probe() was called. Then uart_startup() can be called in serial core. This calls owl_uart_startup() which registers the interrupt handler owl_uart_irq. Now suppose uart_remove_one_port() in serial core is called. This detaches port from the core. This calls owl_uart_release_port(port). This writes NULL to port->membase after iounmap of port->membase from port->dev. During this point, an interrupt is triggered and the interrupt callback owl_uart_irq() is called (parallel with uart_remove_one_port()). This tries to read port->membase to send or receive chars (with spinlock on port->lock). This introduces a race condition on port->membase. QUESTION: Is it possible to remove an active port (without shutdown)?
