tty: serial: imx: console write routing is unsafe on SMP
authorXinyu Chen <xinyu.chen@freescale.com>
Mon, 27 Aug 2012 07:36:51 +0000 (09:36 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 5 Sep 2012 19:44:44 +0000 (12:44 -0700)
commit9ec1882df244c4ee1baa692676fef5e8b0f5487d
treec324ffa8ce389ed628f05ba3c5e9fde1eeb90537
parentfea7a08acb13524b47711625eebea40a0ede69a0
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>
drivers/tty/serial/imx.c