From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shinya Kuribayashi Date: Fri, 16 Nov 2012 01:54:49 +0000 Subject: [PATCH v2 10/10] serial: sh-sci: fix possible race cases on SCSCR register accesses Message-Id: <50A59CE9.5020104@renesas.com> List-Id: References: <509A0658.1010503@renesas.com> <509A0B4E.1030801@renesas.com> <20121116010107.GA6068@kroah.com> <50A59B9B.2010501@renesas.com> In-Reply-To: <50A59B9B.2010501@renesas.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org 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 , 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 --- 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