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Message-Id: <20240820063001.36405-12-john.ogness@linutronix.de>
Date: Tue, 20 Aug 2024 08:35:37 +0206
From: John Ogness <john.ogness@...utronix.de>
To: Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>,
Russell King <linux@...linux.org.uk>,
Tony Lindgren <tony@...mide.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Geert Uytterhoeven <geert+renesas@...der.be>,
Arnd Bergmann <arnd@...db.de>,
Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
Théo Lebrun <theo.lebrun@...tlin.com>,
Linus Walleij <linus.walleij@...aro.org>,
Lino Sanfilippo <l.sanfilippo@...bus.com>,
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
Konrad Dybcio <konrad.dybcio@...aro.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
linux-serial@...r.kernel.org
Subject: [PATCH printk v8 11/35] serial: core: Introduce wrapper to set @uart_port->cons
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@...utronix.de>
Tested-by: Théo Lebrun <theo.lebrun@...tlin.com> # EyeQ5, AMBA-PL011
Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Reviewed-by: Petr Mladek <pmladek@...e.com>
---
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(-)
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 29e4b83e0376..5f9f06911795 100644
--- 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 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);
}
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 8b1644f5411e..7d0134ecd82f 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -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);
}
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 9a18d0b95a41..61c7e1268957 100644
--- 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(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);
@@ -3178,13 +3185,6 @@ 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);
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 8872cd21e70a..2cf03ff2056a 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -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
--
2.39.2
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