On 2024-01-17, "Chang, Junxiao" <junxiao.chang@xxxxxxxxx> wrote: > As you mentioned, same console driver is only registered once. 8250 > console driver is registered once, its "struct console *newcon" > parameter is address of "univ8250_console" which is defined in > drivers\tty\serial\8250\8250_core.c. > > However, in each serial port device is registered, their cons pointer( > "struct console *cons;" in "struct uart_port") will be assigned with > same cons in API serial_core_add_one_port: > > uport->cons = drv->cons; > > That is, multiple similar 8250 uart_port devices have same console > pointer which points to above univ8250_console. Ah. This explains the "(port)->cons->index == (port)->line" check in uart_console(). Thank you for clarifying. > BTW, this issue couldn't be reproduced with v6.6.7-rt17 kernel. The reason for the change is because console registration/unregistration is not related to the port lock. There is a potential race condition if nbcon unlocking is based on the UART port still being registered as a console. We could move the @locked_port flag to the struct uart_port. (Probably renaming it to @nbcon_locked_port.) I think that would be the appropriate fix. John
