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authorShinya Kuribayashi <shinya.kuribayashi.px@renesas.com>2012-11-16 05:54:49 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-11-16 06:02:51 +0400
commit33b48e1633f738c5ae78234c2dd5e3a9ba115437 (patch)
tree09193c93ad60bdd24e34e382439baa129e2aa02b /drivers/tty
parent40f70c03e33a1eed3f3fcd13418e76abad77d117 (diff)
downloadlinux-33b48e1633f738c5ae78234c2dd5e3a9ba115437.tar.xz
serial: sh-sci: fix possible race cases on SCSCR register accesses
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@freescale.com>, 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@renesas.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/sh-sci.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 63a23eadd7e8..d38c0f546032 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1743,6 +1743,7 @@ 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);
@@ -1753,8 +1754,10 @@ 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;
}
@@ -1762,11 +1765,14 @@ 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);