From: Xinyu Chen <xinyu.chen@freescale.com>
Date: Mon, 27 Aug 2012 07:36:51 +0000 (+0200)
Subject: tty: serial: imx: console write routing is unsafe on SMP
X-Git-Tag: v3.2.30~26
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c096552004244868391b29f319ea8889d55abe19;p=pandora-kernel.git

tty: serial: imx: console write routing is unsafe on SMP

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.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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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