On Thu, Jun 24, 2021 at 05:37:38PM +0530, Saubhik Mukherjee wrote: > On 6/23/21 12:46 PM, Johan Hovold wrote: > > On Wed, Jun 23, 2021 at 11:06:53AM +0530, Saubhik Mukherjee wrote: > >> On 6/17/21 4:52 PM, Greg KH wrote: > >>> On Thu, Jun 17, 2021 at 04:34:43PM +0530, Saubhik Mukherjee wrote: > >>>> Suppose the driver is registered and a UART port is added. Once an > >>>> application opens the port, owl_uart_startup is called which registers > >>>> the interrupt handler owl_uart_irq. > >>>> > >>>> We could have the following race condition: > >>>> > >>>> When device is removed, owl_uart_remove is called, which calls > >>>> uart_remove_one_port, which calls owl_uart_release_port, which writes > >>>> NULL to port->membase. At this point parallely, an interrupt could be > >>>> handled by owl_uart_irq which reads port->membase. > >>>> > >>>> This is because it is possible to remove device without closing a port. > >>>> Thus, we need to check it and call owl_uart_shutdown in owl_uart_remove. > > > > No, this makes no sense at all. The port is deregistered and hung up by > > uart_remove_one_port() (and the interrupt line is consequently disabled > > by the driver) before it is released so this can never happen. > > Thanks for the reply. I am not sure I understand. I could not find any > interrupt disabling in owl_uart_remove. Could you point out where/how is > the interrupt line is disabled before releasing the port? The interrupt line is disabled by owl_uart_shutdown(), which is called when uart_remove_one_port() hangs up an open tty. And as I mentioned this happens after deregistering the port (so no new opens) and before releasing the port. Johan
