From: John Ogness Date: Tue, 20 Aug 2024 08:35:37 +0206 Subject: [PATCH 11/54] serial: core: Introduce wrapper to set @uart_port->cons MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.tar.xz Introduce uart_port_set_cons() as a wrapper to set @cons of a uart_port. The wrapper sets @cons under the port lock in order to prevent @cons from disappearing while another context is holding the port lock. This is necessary for a follow-up commit relating to the port lock wrappers, which rely on @cons not changing between lock and unlock. Signed-off-by: John Ogness Tested-by: Théo Lebrun # EyeQ5, AMBA-PL011 Acked-by: Greg Kroah-Hartman Reviewed-by: Petr Mladek Reviewed-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20240820063001.36405-12-john.ogness@linutronix.de Signed-off-by: Petr Mladek Signed-off-by: Sebastian Andrzej Siewior --- drivers/tty/serial/8250/8250_core.c | 6 +++--- drivers/tty/serial/amba-pl011.c | 2 +- drivers/tty/serial/serial_core.c | 16 ++++++++-------- include/linux/serial_core.h | 17 +++++++++++++++++ 4 files changed, 29 insertions(+), 12 deletions(-) --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -423,11 +423,11 @@ static int univ8250_console_setup(struct port = &serial8250_ports[co->index].port; /* link port to console */ - port->cons = co; + uart_port_set_cons(port, co); retval = serial8250_console_setup(port, options, false); if (retval != 0) - port->cons = NULL; + uart_port_set_cons(port, NULL); return retval; } @@ -485,7 +485,7 @@ static int univ8250_console_match(struct continue; co->index = i; - port->cons = co; + uart_port_set_cons(port, co); return serial8250_console_setup(port, options, true); } --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -2480,7 +2480,7 @@ static int pl011_console_match(struct co continue; co->index = i; - port->cons = co; + uart_port_set_cons(port, co); return pl011_console_setup(co, options); } --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -3176,8 +3176,15 @@ static int serial_core_add_one_port(stru state->uart_port = uport; uport->state = state; + /* + * If this port is in use as a console then the spinlock is already + * initialised. + */ + if (!uart_console_registered(uport)) + uart_port_spin_lock_init(uport); + state->pm_state = UART_PM_STATE_UNDEFINED; - uport->cons = drv->cons; + uart_port_set_cons(uport, drv->cons); uport->minor = drv->tty_driver->minor_start + uport->line; uport->name = kasprintf(GFP_KERNEL, "%s%d", drv->dev_name, drv->tty_driver->name_base + uport->line); @@ -3186,13 +3193,6 @@ static int serial_core_add_one_port(stru goto out; } - /* - * If this port is in use as a console then the spinlock is already - * initialised. - */ - if (!uart_console_registered(uport)) - uart_port_spin_lock_init(uport); - if (uport->cons && uport->dev) of_console_check(uport->dev->of_node, uport->cons->name, uport->line); --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -609,6 +609,23 @@ static inline void __uart_port_unlock_ir } /** + * uart_port_set_cons - Safely set the @cons field for a uart + * @up: The uart port to set + * @con: The new console to set to + * + * This function must be used to set @up->cons. It uses the port lock to + * synchronize with the port lock wrappers in order to ensure that the console + * cannot change or disappear while another context is holding the port lock. + */ +static inline void uart_port_set_cons(struct uart_port *up, struct console *con) +{ + unsigned long flags; + + __uart_port_lock_irqsave(up, &flags); + up->cons = con; + __uart_port_unlock_irqrestore(up, flags); +} +/** * uart_port_lock - Lock the UART port * @up: Pointer to UART port structure */