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Message-ID: <20251119100140.830761-11-jirislaby@kernel.org>
Date: Wed, 19 Nov 2025 11:01:40 +0100
From: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To: gregkh@...uxfoundation.org
Cc: linux-serial@...r.kernel.org,
linux-kernel@...r.kernel.org,
"Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Subject: [PATCH 10/10] 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@...nel.org>
---
drivers/tty/serial/serial_core.c | 127 +++++++++++++------------------
1 file changed, 55 insertions(+), 72 deletions(-)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 74018fb8a4e7..c532235f8d55 100644
--- 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);
}
/**
--
2.51.1
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