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From: John Ogness <john.ogness@linutronix.de>
Date: Wed, 17 Apr 2024 12:13:24 +0000
Subject: [PATCH 09/48] 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/6.10/older/patches-6.10.2-rt14.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 <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>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
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
@@ -624,11 +624,11 @@ 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;
}
@@ -686,7 +686,7 @@ 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
@@ -3168,8 +3168,15 @@ 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);
@@ -3178,13 +3185,6 @@ 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
*/
|
