From 9ec1882df244c4ee1baa692676fef5e8b0f5487d Mon Sep 17 00:00:00 2001 From: Xinyu Chen Date: Mon, 27 Aug 2012 09:36:51 +0200 Subject: [PATCH] tty: serial: imx: console write routing is unsafe on SMP The console feature's write routing is unsafe on SMP with the startup/shutdown call. 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 open /dev/console and write with sys_write() The shell goes into the normal uart open/write routing, but the other two go into the console operations. The open routing calls imx serial startup, which will write USR1/2 register without any lock and critical with imx_console_write call. Add a spin_lock for startup/shutdown/console_write routing. This patch is a port from Freescale's Android kernel. Signed-off-by: Xinyu Chen Tested-by: Dirk Behme CC: Sascha Hauer Acked-by: Shawn Guo Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/imx.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index d5c689d6217e..908178fc5a33 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -754,6 +754,7 @@ static int imx_startup(struct uart_port *port) } } + spin_lock_irqsave(&sport->port.lock, flags); /* * Finally, clear and enable interrupts */ @@ -807,7 +808,6 @@ static int imx_startup(struct uart_port *port) /* * Enable modem status interrupts */ - spin_lock_irqsave(&sport->port.lock,flags); imx_enable_ms(&sport->port); spin_unlock_irqrestore(&sport->port.lock,flags); @@ -837,10 +837,13 @@ static void imx_shutdown(struct uart_port *port) { struct imx_port *sport = (struct imx_port *)port; unsigned long temp; + unsigned long flags; + spin_lock_irqsave(&sport->port.lock, flags); temp = readl(sport->port.membase + UCR2); temp &= ~(UCR2_TXEN); writel(temp, sport->port.membase + UCR2); + spin_unlock_irqrestore(&sport->port.lock, flags); if (USE_IRDA(sport)) { struct imxuart_platform_data *pdata; @@ -869,12 +872,14 @@ static void imx_shutdown(struct uart_port *port) * Disable all interrupts, port and break condition. */ + spin_lock_irqsave(&sport->port.lock, flags); temp = readl(sport->port.membase + UCR1); temp &= ~(UCR1_TXMPTYEN | UCR1_RRDYEN | UCR1_RTSDEN | UCR1_UARTEN); if (USE_IRDA(sport)) temp &= ~(UCR1_IREN); writel(temp, sport->port.membase + UCR1); + spin_unlock_irqrestore(&sport->port.lock, flags); } static void @@ -1217,6 +1222,9 @@ imx_console_write(struct console *co, const char *s, unsigned int count) struct imx_port *sport = imx_ports[co->index]; struct imx_port_ucrs old_ucr; unsigned int ucr1; + unsigned long flags; + + spin_lock_irqsave(&sport->port.lock, flags); /* * First, save UCR1/2/3 and then disable interrupts @@ -1242,6 +1250,8 @@ imx_console_write(struct console *co, const char *s, unsigned int count) while (!(readl(sport->port.membase + USR2) & USR2_TXDC)); imx_port_ucrs_restore(&sport->port, &old_ucr); + + spin_unlock_irqrestore(&sport->port.lock, flags); } /* -- 2.20.1