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 <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> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -754,6 +754,7 @@ static int imx_startup(struct uart_port *port)
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}
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}
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spin_lock_irqsave(&sport->port.lock, flags);
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/*
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* Finally, clear and enable interrupts
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*/
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@ -807,7 +808,6 @@ static int imx_startup(struct uart_port *port)
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/*
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* Enable modem status interrupts
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*/
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spin_lock_irqsave(&sport->port.lock,flags);
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imx_enable_ms(&sport->port);
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spin_unlock_irqrestore(&sport->port.lock,flags);
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@ -837,10 +837,13 @@ static void imx_shutdown(struct uart_port *port)
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{
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struct imx_port *sport = (struct imx_port *)port;
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unsigned long temp;
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unsigned long flags;
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spin_lock_irqsave(&sport->port.lock, flags);
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temp = readl(sport->port.membase + UCR2);
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temp &= ~(UCR2_TXEN);
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writel(temp, sport->port.membase + UCR2);
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spin_unlock_irqrestore(&sport->port.lock, flags);
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if (USE_IRDA(sport)) {
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struct imxuart_platform_data *pdata;
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@ -869,12 +872,14 @@ static void imx_shutdown(struct uart_port *port)
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* Disable all interrupts, port and break condition.
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*/
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spin_lock_irqsave(&sport->port.lock, flags);
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temp = readl(sport->port.membase + UCR1);
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temp &= ~(UCR1_TXMPTYEN | UCR1_RRDYEN | UCR1_RTSDEN | UCR1_UARTEN);
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if (USE_IRDA(sport))
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temp &= ~(UCR1_IREN);
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writel(temp, sport->port.membase + UCR1);
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spin_unlock_irqrestore(&sport->port.lock, flags);
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}
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static void
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@ -1217,6 +1222,9 @@ imx_console_write(struct console *co, const char *s, unsigned int count)
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struct imx_port *sport = imx_ports[co->index];
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struct imx_port_ucrs old_ucr;
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unsigned int ucr1;
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unsigned long flags;
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spin_lock_irqsave(&sport->port.lock, flags);
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/*
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* First, save UCR1/2/3 and then disable interrupts
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@ -1242,6 +1250,8 @@ imx_console_write(struct console *co, const char *s, unsigned int count)
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while (!(readl(sport->port.membase + USR2) & USR2_TXDC));
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imx_port_ucrs_restore(&sport->port, &old_ucr);
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spin_unlock_irqrestore(&sport->port.lock, flags);
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}
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/*
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