From 42b6a1baa3ec18de2eb15baa250da6203eeb2d39 Mon Sep 17 00:00:00 2001
From: Randy Witt <rewitt@declaratino.com>
Date: Thu, 17 Oct 2013 16:56:47 -0400
Subject: [PATCH] serial_core: Don't re-initialize a previously initialized
 spinlock.

The uart_set_options() code unconditionally initalizes the spinlock
on the port. This can cause a deadlock in some situations.

One instance that exposed the problem, was when writing to
/sys/module/kgdboc/parameters/kgdboc to use ttyS0 when the console
is already running on ttyS0. If the spinlock is re-initialized
while the lock is held due to output to the console, there
is a deadlock.

Assume the spinlock is initialized if the port is a console.

Signed-off-by: Randy Witt <rewitt@declaratino.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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