linux-kernel - [PATCH 1/1] tty: serial: samsung: add spin_lock for interrupt and console

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Message-Id: <20220405033854.110374-2-jaewon02.kim@samsung.com>
Date:   Tue,  5 Apr 2022 12:38:54 +0900
From:   Jaewon Kim <jaewon02.kim@...sung.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-samsung-soc@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chanho Park <chanho61.park@...sung.com>,
        Jaewon Kim <jaewon02.kim@...sung.com>
Subject: [PATCH 1/1] tty: serial: samsung: add spin_lock for interrupt and
 console_write

The console_write and IRQ handler can run concurrently.
Problems may occurs console_write is continuously executed while
the IRQ handler is running.

Signed-off-by: Jaewon Kim <jaewon02.kim@...sung.com>
---
 drivers/tty/serial/samsung_tty.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index e1585fbae909..d362e8e114f1 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -2480,12 +2480,26 @@ s3c24xx_serial_console_write(struct console *co, const char *s,
 			     unsigned int count)
 {
 	unsigned int ucon = rd_regl(cons_uart, S3C2410_UCON);
+	unsigned long flags;
+	int locked = 1;
 
 	/* not possible to xmit on unconfigured port */
 	if (!s3c24xx_port_configured(ucon))
 		return;
 
+	local_irq_save(flags);
+	if (cons_uart->sysrq)
+		locked = 0;
+	else if (oops_in_progress)
+		locked = spin_trylock(&cons_uart->lock);
+	else
+		spin_lock(&cons_uart->lock);
+
 	uart_console_write(cons_uart, s, count, s3c24xx_serial_console_putchar);
+
+	if (locked)
+		spin_unlock(&cons_uart->lock);
+	local_irq_restore(flags);
 }
 
 /* Shouldn't be __init, as it can be instantiated from other module */
-- 
2.35.1