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serial: core: Introduce wrapper to set @uart_port->cons

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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 <john.ogness@linutronix.de>
Tested-by: Théo Lebrun <theo.lebrun@bootlin.com> # EyeQ5, AMBA-PL011
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240820063001.36405-12-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
John Ogness 2024-08-20 08:35:37 +02:06 committed by Petr Mladek
parent 77e73c0687
commit eabd4600da
4 changed files with 29 additions and 12 deletions
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6
drivers/tty/serial/8250/8250_core.c
View File

@ -423,11 +423,11 @@ static int univ8250_console_setup(struct console *co, char *options)
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 console *co, char *name, int idx,
continue;
co->index = i;
port->cons = co;
uart_port_set_cons(port, co);
return serial8250_console_setup(port, options, true);
}

2
drivers/tty/serial/amba-pl011.c
View File

@ -2480,7 +2480,7 @@ static int pl011_console_match(struct console *co, char *name, int idx,
continue;
co->index = i;
port->cons = co;
uart_port_set_cons(port, co);
return pl011_console_setup(co, options);
}

16
drivers/tty/serial/serial_core.c
View File

@ -3176,8 +3176,15 @@ static int serial_core_add_one_port(struct uart_driver *drv, struct uart_port *u
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(struct uart_driver *drv, struct uart_port *u
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);

17
include/linux/serial_core.h
View File

@ -608,6 +608,23 @@ static inline void __uart_port_unlock_irqrestore(struct uart_port *up, unsigned
spin_unlock_irqrestore(&up->lock, flags);
}
/**
* 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