[PATCH] serial: xilinx_uartps: publish console_port with release semantics

[PATCH] serial: xilinx_uartps: publish console_port with release semantics

[Jaidev Shastri via B4 Relay]

From: Jaidev Shastri <jaidevshastri@vt.edu>

cdns_uart_probe() assigns the first probed port to console_port with a
plain store once the port is set up. cdns_uart_console_write() and
cdns_uart_console_setup() read it with plain loads.

Store it with smp_store_release() and read it with smp_load_acquire().

Found with MBCheck, a static herd7-based memory consistency checker.

Signed-off-by: Jaidev Shastri <jaidevshastri@vt.edu>
---
 drivers/tty/serial/xilinx_uartps.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index a072b75db..59e0d388d 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1371,7 +1371,8 @@ static struct uart_port *console_port;
 static void cdns_uart_console_write(struct console *co, const char *s,
 				unsigned int count)
 {
-	struct uart_port *port = console_port;
+	/* Pairs with the smp_store_release() in cdns_uart_probe(). */
+	struct uart_port *port = smp_load_acquire(&console_port);
 	unsigned long flags;
 	unsigned int imr, ctrl;
 	int locked = 1;
@@ -1414,7 +1415,8 @@ static void cdns_uart_console_write(struct console *co, const char *s,
  */
 static int cdns_uart_console_setup(struct console *co, char *options)
 {
-	struct uart_port *port = console_port;
+	/* Pairs with the smp_store_release() in cdns_uart_probe(). */
+	struct uart_port *port = smp_load_acquire(&console_port);
 
 	int baud = 9600;
 	int bits = 8;
@@ -1812,7 +1814,8 @@ static int cdns_uart_probe(struct platform_device *pdev)
 	 */
 	if (!console_port) {
 		cdns_uart_console.index = id;
-		console_port = port;
+		/* Pairs with the smp_load_acquire() in the console callbacks. */
+		smp_store_release(&console_port, port);
 	}
 #endif
 	if (cdns_uart_data->port->rs485.flags & SER_RS485_ENABLED)

---
base-commit: 93f51579e7df248780214094418f205253383cc5
change-id: 20260921-mb-uartps-ce1b1ca29a83

Best regards,
--  
Jaidev Shastri <jaidevshastri@vt.edu>

Re: [PATCH] serial: xilinx_uartps: publish console_port with release semantics

[Greg Kroah-Hartman]

On Mon, Sep 21, 2026 at 09:21:13PM -0400, Jaidev Shastri via B4 Relay wrote:
> From: Jaidev Shastri <jaidevshastri@vt.edu>
> 
> cdns_uart_probe() assigns the first probed port to console_port with a
> plain store once the port is set up. cdns_uart_console_write() and
> cdns_uart_console_setup() read it with plain loads.
> 
> Store it with smp_store_release() and read it with smp_load_acquire().
> 
> Found with MBCheck, a static herd7-based memory consistency checker.

And how was this tested?  The shashiko review bot shows where your tool
looks wrong...