linux-kernel - [PATCH v2] serial: stm32: optimize spin lock usage

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Date:   Mon, 12 Apr 2021 17:31:38 +0800
From:   dillon.minfei@...il.com
To:     gregkh@...uxfoundation.org, jirislaby@...nel.org,
        mcoquelin.stm32@...il.com, alexandre.torgue@...s.st.com,
        lkp@...el.com
Cc:     linux-serial@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kbuild-all@...ts.01.org, clang-built-linux@...glegroups.com,
        dillon min <dillon.minfei@...il.com>,
        Gerald Baeza <gerald.baeza@...s.st.com>,
        Erwan Le Ray <erwan.leray@...s.st.com>
Subject: [PATCH v2] serial: stm32: optimize spin lock usage

From: dillon min <dillon.minfei@...il.com>

To avoid potential deadlock in spin_lock usage, use spin_lock_irqsave,
spin_trylock_irqsave(), spin_unlock_irqrestore() in process context.

remove unused local_irq_save/restore call.

Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc: Gerald Baeza <gerald.baeza@...s.st.com>
Cc: Erwan Le Ray <erwan.leray@...s.st.com>
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: dillon min <dillon.minfei@...il.com>
---
v2: remove unused code from stm32_usart_threaded_interrupt() according from
    Greg's review.

 drivers/tty/serial/stm32-usart.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index b3675cf25a69..b1ba5e36e36e 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -1354,13 +1354,12 @@ static void stm32_usart_console_write(struct console *co, const char *s,
 	u32 old_cr1, new_cr1;
 	int locked = 1;
 
-	local_irq_save(flags);
 	if (port->sysrq)
 		locked = 0;
 	else if (oops_in_progress)
-		locked = spin_trylock(&port->lock);
+		locked = spin_trylock_irqsave(&port->lock, flags);
 	else
-		spin_lock(&port->lock);
+		spin_lock_irqsave(&port->lock, flags);
 
 	/* Save and disable interrupts, enable the transmitter */
 	old_cr1 = readl_relaxed(port->membase + ofs->cr1);
@@ -1374,8 +1373,7 @@ static void stm32_usart_console_write(struct console *co, const char *s,
 	writel_relaxed(old_cr1, port->membase + ofs->cr1);
 
 	if (locked)
-		spin_unlock(&port->lock);
-	local_irq_restore(flags);
+		spin_unlock_irqrestore(&port->lock, flags);
 }
 
 static int stm32_usart_console_setup(struct console *co, char *options)
-- 
2.7.4