This is a note to let you know that I've just added the patch titled
tty: serial: imx: console write routing is unsafe on SMP
to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From 9ec1882df244c4ee1baa692676fef5e8b0f5487d Mon Sep 17 00:00:00 2001
From: Xinyu Chen <[email protected]>
Date: Mon, 27 Aug 2012 09:36:51 +0200
Subject: 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 <[email protected]>
Tested-by: Dirk Behme <[email protected]>
CC: Sascha Hauer <[email protected]>
Acked-by: Shawn Guo <[email protected]>
Cc: stable <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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 d5c689d6..908178f 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);
}
/*
--
1.7.12.176.g3fc0e4c
--
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