In the previous commit, console write function (serial_console_write)
is changed to disable SCI interrupts while printing console strings.
This introduces possible race cases in the serial startup / shutdown
functions on SMP systems.
This patch fixes the sh-sci in the same way as commit 9ec1882df2
(tty: serial: imx: console write routing is unsafe on SMP, from
Xinyu Chen <xinyu.chen@xxxxxxxxxxxxx>, 2012-08-27) did.
There could be several consumers of the console,
* the kernel printk
* the init process using /dev/kmsg to call printk to show log
* shell, which opens /dev/console and writes with sys_write()
The shell goes into the normal UART open() and write() system calls,
while the other two go into the console operations. The open() call
invokes serial startup function (sci_startup), which will write to
the SCSCR register (to enable or disable SCI interrupts) without any
locking. This will conflict with the console serial function.
Add spinlock protections in sci_startup() and sci_shutdown() properly.
Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi.px@xxxxxxxxxxx>
---
drivers/tty/serial/sh-sci.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 0b8d029..8e3c7f7 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1742,6 +1742,7 @@ static inline void sci_free_dma(struct uart_port *port)
static int sci_startup(struct uart_port *port)
{
struct sci_port *s = to_sci_port(port);
+ unsigned long flags;
int ret;
dev_dbg(port->dev, "%s(%d)\n", __func__, port->line);
@@ -1752,8 +1753,10 @@ static int sci_startup(struct uart_port *port)
sci_request_dma(port);
+ spin_lock_irqsave(&port->lock, flags);
sci_start_tx(port);
sci_start_rx(port);
+ spin_unlock_irqrestore(&port->lock, flags);
return 0;
}
@@ -1761,11 +1764,14 @@ static int sci_startup(struct uart_port *port)
static void sci_shutdown(struct uart_port *port)
{
struct sci_port *s = to_sci_port(port);
+ unsigned long flags;
dev_dbg(port->dev, "%s(%d)\n", __func__, port->line);
+ spin_lock_irqsave(&port->lock, flags);
sci_stop_rx(port);
sci_stop_tx(port);
+ spin_unlock_irqrestore(&port->lock, flags);
sci_free_dma(port);
sci_free_irq(s);
--
1.7.12.4
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