From e4b3ccb5426bec41cd5ecf6ad3f655e9b8cb000f Mon Sep 17 00:00:00 2001 From: Xinyu Chen Date: Fri, 2 Dec 2011 14:38:21 +0800 Subject: [PATCH] ENGR00163703 uart: console write routing is unsafe on SMP The console feature's write routing is unsafe on SMP with the startup/shutdown call. It happend to cause Android bootup without shell runnable. Actually on Android boot, there's 3 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. Here add spin_lock for startup/shutdown/console_write routing. Remove the imx_setup_ufcr() call on startup when CONSOLE enabled, as this will cause clock reinit, and output garbage. Signed-off-by: Xinyu Chen --- drivers/tty/serial/imx.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 0a8c6d0f963a..e484c82b6de9 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -902,7 +902,9 @@ static int imx_startup(struct uart_port *port) unsigned long flags, temp; struct tty_struct *tty; +#ifndef CONFIG_SERIAL_CORE_CONSOLE imx_setup_ufcr(sport, 0); +#endif /* disable the DREN bit (Data Ready interrupt enable) before * requesting IRQs @@ -976,6 +978,7 @@ static int imx_startup(struct uart_port *port) INIT_WORK(&sport->tsk_dma_rx, dma_rx_work); } + spin_lock_irqsave(&sport->port.lock, flags); /* * Finally, clear and enable interrupts */ @@ -1040,7 +1043,6 @@ 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); @@ -1074,10 +1076,13 @@ 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; @@ -1106,12 +1111,15 @@ 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); + if (sport->enable_dma) imx_uart_dma_exit(sport); } @@ -1272,6 +1280,7 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios, if (UART_ENABLE_MS(&sport->port, termios->c_cflag)) imx_enable_ms(&sport->port); + } static const char *imx_type(struct uart_port *port) @@ -1392,7 +1401,9 @@ imx_console_write(struct console *co, const char *s, unsigned int count) { 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 */ @@ -1418,6 +1429,7 @@ imx_console_write(struct console *co, const char *s, unsigned int count) writel(old_ucr1, sport->port.membase + UCR1); writel(old_ucr2, sport->port.membase + UCR2); + spin_unlock_irqrestore(&sport->port.lock, flags); } /* -- 2.39.5