linux-kernel - Re: [PATCH v2 1/2] serial: sifive: lock port in startup()/shutdown() callbacks

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Message-Id: <20250330011610.388077-1-ryotkkr98@gmail.com>
Date: Sun, 30 Mar 2025 10:16:10 +0900
From: Ryo Takakura <ryotkkr98@...il.com>
To: alex@...ti.fr,
	aou@...s.berkeley.edu,
	gregkh@...uxfoundation.org,
	jirislaby@...nel.org,
	john.ogness@...utronix.de,
	palmer@...belt.com,
	paul.walmsley@...ive.com,
	pmladek@...e.com,
	samuel.holland@...ive.com,
	bigeasy@...utronix.de,
	conor.dooley@...rochip.com,
	u.kleine-koenig@...libre.com,
	lkp@...el.com
Cc: linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	linux-serial@...r.kernel.org,
	stable@...r.kernel.org,
	oe-kbuild-all@...ts.linux.dev,
	Ryo Takakura <ryotkkr98@...il.com>
Subject: Re: [PATCH v2 1/2] serial: sifive: lock port in startup()/shutdown() callbacks

startup()/shutdown() callbacks access SIFIVE_SERIAL_IE_OFFS.
The register is also accessed from write() callback.

If console were printing and startup()/shutdown() callback
gets called, its access to the register could be overwritten.

Add port->lock to startup()/shutdown() callbacks to make sure
their access to SIFIVE_SERIAL_IE_OFFS is synchronized against
write() callback.

Signed-off-by: Ryo Takakura <ryotkkr98@...il.com>
Cc: stable@...r.kernel.org
---

Hi,

I'm sorry that I wasn't aware of how Cc stable should be done. 

I added Cc for stable but please tell me if this patch should be
resent or if there is any that is missing.

Sincerely,
Ryo Takakura

---
 drivers/tty/serial/sifive.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c
index 5904a2d4c..054a8e630 100644
--- a/drivers/tty/serial/sifive.c
+++ b/drivers/tty/serial/sifive.c
@@ -563,8 +563,11 @@ static void sifive_serial_break_ctl(struct uart_port *port, int break_state)
 static int sifive_serial_startup(struct uart_port *port)
 {
 	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+	unsigned long flags;
 
+	uart_port_lock_irqsave(&ssp->port, &flags);
 	__ssp_enable_rxwm(ssp);
+	uart_port_unlock_irqrestore(&ssp->port, flags);
 
 	return 0;
 }
@@ -572,9 +575,12 @@ static int sifive_serial_startup(struct uart_port *port)
 static void sifive_serial_shutdown(struct uart_port *port)
 {
 	struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+	unsigned long flags;
 
+	uart_port_lock_irqsave(&ssp->port, &flags);
 	__ssp_disable_rxwm(ssp);
 	__ssp_disable_txwm(ssp);
+	uart_port_unlock_irqrestore(&ssp->port, flags);
 }
 
 /**
-- 
2.34.1