serial: serial_core: use guard()s

Use guards in the serial_core code. This improves readability, makes
error handling easier, and marks locked portions of code explicit. All
that while being sure the lock is unlocked.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://patch.msgid.link/20251119100140.830761-11-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 74018fb8a4e71dfe3a066e8de671c4151fdd4473..c532235f8d555366a51eb86dc373dcb65733b56d 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1034,9 +1034,8 @@ static int uart_set_info_user(struct tty_struct *tty, struct serial_struct *ss)
 {
        struct uart_state *state = tty->driver_data;
        struct tty_port *port = &state->port;
-       int retval;
 
-       down_write(&tty->termios_rwsem);
+       guard(rwsem_write)(&tty->termios_rwsem);
        /*
         * This semaphore protects port->count.  It is also
         * very useful to prevent opens.  Also, take the
@@ -1044,11 +1043,8 @@ static int uart_set_info_user(struct tty_struct *tty, struct serial_struct *ss)
         * module insertion/removal doesn't change anything
         * under us.
         */
-       mutex_lock(&port->mutex);
-       retval = uart_set_info(tty, port, state, ss);
-       mutex_unlock(&port->mutex);
-       up_write(&tty->termios_rwsem);
-       return retval;
+       guard(mutex)(&port->mutex);
+       return uart_set_info(tty, port, state, ss);
 }
 
 /**
@@ -1562,10 +1558,8 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
 
        /* This ioctl doesn't rely on the hardware to be present. */
        if (cmd == TIOCSERCONFIG) {
-               down_write(&tty->termios_rwsem);
-               ret = uart_do_autoconfig(tty, state);
-               up_write(&tty->termios_rwsem);
-               return ret;
+               guard(rwsem_write)(&tty->termios_rwsem);
+               return uart_do_autoconfig(tty, state);
        }
 
        if (tty_io_error(tty))
@@ -1579,46 +1573,46 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
        if (cmd == TIOCSRS485)
                down_write(&tty->termios_rwsem);
 
-       mutex_lock(&port->mutex);
-       uport = uart_port_check(state);
+       scoped_guard(mutex, &port->mutex) {
+               uport = uart_port_check(state);
 
-       if (!uport || tty_io_error(tty)) {
-               ret = -EIO;
-               goto out_up;
-       }
+               if (!uport || tty_io_error(tty)) {
+                       ret = -EIO;
+                       break;
+               }
 
-       /*
-        * All these rely on hardware being present and need to be
-        * protected against the tty being hung up.
-        */
+               /*
+                * All these rely on hardware being present and need to be
+                * protected against the tty being hung up.
+                */
 
-       switch (cmd) {
-       case TIOCSERGETLSR: /* Get line status register */
-               ret = uart_get_lsr_info(tty, state, uarg);
-               break;
+               switch (cmd) {
+               case TIOCSERGETLSR: /* Get line status register */
+                       ret = uart_get_lsr_info(tty, state, uarg);
+                       break;
 
-       case TIOCGRS485:
-               ret = uart_get_rs485_config(uport, uarg);
-               break;
+               case TIOCGRS485:
+                       ret = uart_get_rs485_config(uport, uarg);
+                       break;
 
-       case TIOCSRS485:
-               ret = uart_set_rs485_config(tty, uport, uarg);
-               break;
+               case TIOCSRS485:
+                       ret = uart_set_rs485_config(tty, uport, uarg);
+                       break;
 
-       case TIOCSISO7816:
-               ret = uart_set_iso7816_config(state->uart_port, uarg);
-               break;
+               case TIOCSISO7816:
+                       ret = uart_set_iso7816_config(state->uart_port, uarg);
+                       break;
 
-       case TIOCGISO7816:
-               ret = uart_get_iso7816_config(state->uart_port, uarg);
-               break;
-       default:
-               if (uport->ops->ioctl)
-                       ret = uport->ops->ioctl(uport, cmd, arg);
-               break;
+               case TIOCGISO7816:
+                       ret = uart_get_iso7816_config(state->uart_port, uarg);
+                       break;
+               default:
+                       if (uport->ops->ioctl)
+                               ret = uport->ops->ioctl(uport, cmd, arg);
+                       break;
+               }
        }
-out_up:
-       mutex_unlock(&port->mutex);
+
        if (cmd == TIOCSRS485)
                up_write(&tty->termios_rwsem);
 
@@ -1634,11 +1628,10 @@ static void uart_set_ldisc(struct tty_struct *tty)
        if (!tty_port_initialized(port))
                return;
 
-       mutex_lock(&state->port.mutex);
+       guard(mutex)(&state->port.mutex);
        uport = uart_port_check(state);
        if (uport && uport->ops->set_ldisc)
                uport->ops->set_ldisc(uport, &tty->termios);
-       mutex_unlock(&state->port.mutex);
 }
 
 static void uart_set_termios(struct tty_struct *tty,
@@ -1712,9 +1705,8 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
 
                state = drv->state + tty->index;
                port = &state->port;
-               spin_lock_irq(&port->lock);
+               guard(spinlock_irq)(&port->lock);
                --port->count;
-               spin_unlock_irq(&port->lock);
                return;
        }
 
@@ -1826,20 +1818,18 @@ static void uart_hangup(struct tty_struct *tty)
        struct uart_state *state = tty->driver_data;
        struct tty_port *port = &state->port;
        struct uart_port *uport;
-       unsigned long flags;
 
        pr_debug("uart_hangup(%d)\n", tty->index);
 
-       mutex_lock(&port->mutex);
+       guard(mutex)(&port->mutex);
        uport = uart_port_check(state);
        WARN(!uport, "hangup of detached port!\n");
 
        if (tty_port_active(port)) {
                uart_flush_buffer(tty);
                uart_shutdown(tty, state);
-               spin_lock_irqsave(&port->lock, flags);
-               port->count = 0;
-               spin_unlock_irqrestore(&port->lock, flags);
+               scoped_guard(spinlock_irqsave, &port->lock)
+                       port->count = 0;
                tty_port_set_active(port, false);
                tty_port_tty_set(port, NULL);
                if (uport && !uart_console(uport))
@@ -1847,7 +1837,6 @@ static void uart_hangup(struct tty_struct *tty)
                wake_up_interruptible(&port->open_wait);
                wake_up_interruptible(&port->delta_msr_wait);
        }
-       mutex_unlock(&port->mutex);
 }
 
 /* uport == NULL if uart_port has already been removed */
@@ -2952,11 +2941,11 @@ static ssize_t console_show(struct device *dev,
        struct uart_port *uport;
        bool console = false;
 
-       mutex_lock(&port->mutex);
-       uport = uart_port_check(state);
-       if (uport)
-               console = uart_console_registered(uport);
-       mutex_unlock(&port->mutex);
+       scoped_guard(mutex, &port->mutex) {
+               uport = uart_port_check(state);
+               if (uport)
+                       console = uart_console_registered(uport);
+       }
 
        return sprintf(buf, "%c\n", console ? 'Y' : 'N');
 }
@@ -3141,17 +3130,14 @@ static void serial_core_remove_one_port(struct uart_driver *drv,
        struct tty_port *port = &state->port;
        struct uart_port *uart_port;
 
-       mutex_lock(&port->mutex);
-       uart_port = uart_port_check(state);
-       if (uart_port != uport)
-               dev_alert(uport->dev, "Removing wrong port: %p != %p\n",
-                         uart_port, uport);
+       scoped_guard(mutex, &port->mutex) {
+               uart_port = uart_port_check(state);
+               if (uart_port != uport)
+                       dev_alert(uport->dev, "Removing wrong port: %p != %p\n", uart_port, uport);
 
-       if (!uart_port) {
-               mutex_unlock(&port->mutex);
-               return;
+               if (!uart_port)
+                       return;
        }
-       mutex_unlock(&port->mutex);
 
        /*
         * Remove the devices from the tty layer
@@ -3180,11 +3166,10 @@ static void serial_core_remove_one_port(struct uart_driver *drv,
        uport->type = PORT_UNKNOWN;
        uport->port_dev = NULL;
 
-       mutex_lock(&port->mutex);
+       guard(mutex)(&port->mutex);
        WARN_ON(atomic_dec_return(&state->refcount) < 0);
        wait_event(state->remove_wait, !atomic_read(&state->refcount));
        state->uart_port = NULL;
-       mutex_unlock(&port->mutex);
 }
 
 /**
@@ -3337,7 +3322,7 @@ void serial_core_unregister_port(struct uart_driver *drv, struct uart_port *port
        struct serial_ctrl_device *ctrl_dev = serial_core_get_ctrl_dev(port_dev);
        int ctrl_id = port->ctrl_id;
 
-       mutex_lock(&port_mutex);
+       guard(mutex)(&port_mutex);
 
        port->flags |= UPF_DEAD;
 
@@ -3349,8 +3334,6 @@ void serial_core_unregister_port(struct uart_driver *drv, struct uart_port *port
        /* Drop the serial core controller device if no ports are using it */
        if (!serial_core_ctrl_find(drv, phys_dev, ctrl_id))
                serial_base_ctrl_device_remove(ctrl_dev);
-
-       mutex_unlock(&port_mutex);
 }
 
 /**