On 24. 06. 22, 22:42, Ilpo Järvinen wrote:
To be able to alter ADDRB within ->rs485_config(), take termios_rwsem
before calling ->rs485_config() and pass termios.
OK, FTR, worth noting the tty->termios_rwsem -> port->mutex lock chain
is preexisting.
Anyway, I'm not sure I buy the above. Why is termios_rwsem needed to
alter ADDRB?
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 621fc15e2e54..44c3785445e3 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
...
@@ -1511,6 +1511,10 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
if (ret != -ENOIOCTLCMD)
goto out;
+ /* rs485_config requires more locking than others */
+ if (cmd == TIOCGRS485)
+ down_write(&tty->termios_rwsem);
+
mutex_lock(&port->mutex);
uport = uart_port_check(state);
...
@@ -1551,6 +1555,8 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
}
out_up:
mutex_unlock(&port->mutex);
+ if (cmd == TIOCGRS485)
+ up_write(&tty->termios_rwsem);
out:
return ret;
}
thanks,
--
js
