linux-kernel - [PATCH] tty: serial: samsung_tty: avoid dev

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Message-ID: <aXny9km6N1v9eoXU@zall.org>
Date: Wed, 28 Jan 2026 11:28:54 +0000
From: Alyssa Milburn <amilburn@...l.org>
To: Krzysztof Kozlowski <krzk@...nel.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Faraz Ata <faraz.ata@...sung.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Cc: Alyssa Milburn <amilburn@...l.org>
Subject: [PATCH] tty: serial: samsung_tty: avoid dev_dbg deadlock

commit a05025d0ce72 ("tty: serial: samsung_tty: use standard
debugging macros") changed the debug prints to dev_dbg, which can
result in deadlocks:

s3c24xx_serial_set_termios can be called with the port lock, and then
calls dev_dbg, which needs the console mutex. At the same time,
s3c24xx_serial_console_write can be called with the console lock
(e.g., inside console_unlock), and needs the port lock.

To avoid this, move one dev_dbg call and just delete the other.

Signed-off-by: Alyssa Milburn <amilburn@...l.org>
---
 drivers/tty/serial/samsung_tty.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index 563688c50751..4a82779a4c38 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -1582,12 +1582,12 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
 		ulcon |= S3C2410_LCON_PNONE;
 	}
 
-	uart_port_lock_irqsave(port, &flags);
-
 	dev_dbg(port->dev,
 		"setting ulcon to %08x, brddiv to %d, udivslot %08x\n",
 		ulcon, quot, udivslot);
 
+	uart_port_lock_irqsave(port, &flags);
+
 	wr_regl(port, S3C2410_ULCON, ulcon);
 	wr_regl(port, S3C2410_UBRDIV, quot);
 
@@ -1607,12 +1607,6 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
 	if (ourport->info->has_divslot)
 		wr_regl(port, S3C2443_DIVSLOT, udivslot);
 
-	dev_dbg(port->dev,
-		"uart: ulcon = 0x%08x, ucon = 0x%08x, ufcon = 0x%08x\n",
-		rd_regl(port, S3C2410_ULCON),
-		rd_regl(port, S3C2410_UCON),
-		rd_regl(port, S3C2410_UFCON));
-
 	/*
 	 * Update the per-port timeout.
 	 */
-- 
2.52.0