3.2-stable review patch. If anyone has any objections, please let me know.
------------------ From: Xinyu Chen <xinyu.c...@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.c...@freescale.com> Tested-by: Dirk Behme <dirk.be...@de.bosch.com> CC: Sascha Hauer <s.ha...@pengutronix.de> Acked-by: Shawn Guo <shawn....@linaro.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <b...@decadent.org.uk> --- 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 @@ -725,6 +725,7 @@ static int imx_startup(struct uart_port } } + spin_lock_irqsave(&sport->port.lock, flags); /* * Finally, clear and enable interrupts */ @@ -778,7 +779,6 @@ 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); @@ -808,10 +808,13 @@ 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; @@ -840,12 +843,14 @@ 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 @@ -1119,6 +1124,9 @@ imx_console_write(struct console *co, co { struct imx_port *sport = imx_ports[co->index]; unsigned int old_ucr1, old_ucr2, ucr1; + unsigned long flags; + + spin_lock_irqsave(&sport->port.lock, flags); /* * First, save UCR1/2 and then disable interrupts @@ -1145,6 +1153,8 @@ imx_console_write(struct console *co, co writel(old_ucr1, sport->port.membase + UCR1); writel(old_ucr2, sport->port.membase + UCR2); + + spin_unlock_irqrestore(&sport->port.lock, flags); } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/