Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [ 139/218] tty: serial: imx: console write routing is unsafe on SMP | Date | Fri, 28 Sep 2012 13:15:56 -0700 |
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3.4-stable review patch. If anyone has any objections, please let me know.
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From: Xinyu Chen <xinyu.chen@freescale.com>
commit 9ec1882df244c4ee1baa692676fef5e8b0f5487d upstream.
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 <xinyu.chen@freescale.com> Tested-by: Dirk Behme <dirk.behme@de.bosch.com> CC: Sascha Hauer <s.hauer@pengutronix.de> Acked-by: Shawn Guo <shawn.guo@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/tty/serial/imx.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
--- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -756,6 +756,7 @@ static int imx_startup(struct uart_port } } + spin_lock_irqsave(&sport->port.lock, flags); /* * Finally, clear and enable interrupts */ @@ -809,7 +810,6 @@ static int imx_startup(struct uart_port /* * Enable modem status interrupts */ - spin_lock_irqsave(&sport->port.lock,flags); imx_enable_ms(&sport->port); spin_unlock_irqrestore(&sport->port.lock,flags); @@ -839,10 +839,13 @@ static void imx_shutdown(struct uart_por { 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; @@ -871,12 +874,14 @@ static void imx_shutdown(struct uart_por * 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 @@ -1219,6 +1224,9 @@ imx_console_write(struct console *co, co 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 @@ -1244,6 +1252,8 @@ imx_console_write(struct console *co, co while (!(readl(sport->port.membase + USR2) & USR2_TXDC)); imx_port_ucrs_restore(&sport->port, &old_ucr); + + spin_unlock_irqrestore(&sport->port.lock, flags); } /*
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