[PATCH] serial: fix serial port lock init

[Ingo Molnar <mingo@elte.hu>]

> [   31.099528] BUG: spinlock bad magic on CPU#1, agetty/2608

the patch below fixes this. There's another incarnation of the bug that 
i bisected today, a spontaneous reboot crash with certain configs:

| b70ac7718579b5cbf3bdd74fd01132d1c91596f4 is first bad commit
| commit b70ac7718579b5cbf3bdd74fd01132d1c91596f4
| Author: David Miller <davem@davemloft.net>
| Date:   Mon Oct 13 10:36:31 2008 +0100
|
|     serial: allow 8250 to be used on sparc

 # bad:  [e7f2f991] Merge phase #5 (misc) of git://git.kernel.org/pub/
 # good: [3fa8749e] Linux 2.6.27
 # good: [4dd9ec49] Merge git://git.kernel.org/pub/scm/linux/kernel/gi
 # good: [5c3c4d9b] Merge git://git.kernel.org/pub/scm/linux/kernel/gi
 # good: [1a2217a9] Merge git://git.kernel.org/pub/scm/linux/kernel/gi
 # good: [cf81978d] i386: convert hardware exception 15 to an interrup
 # good: [c00193f9] Merge branches 'oprofile-v2' and 'timers/hpet' int
 # bad:  [8f520021] tty: Termios locking - sort out real_tty confusion
 # good: [f1ddfd95] ip2: init/deinit cleanup
 # bad:  [b70ac771] serial: allow 8250 to be used on sparc
 # good: [9bde10a4] serial-make-uart_ports-ioport-unsigned-long-fix
 # good: [43b11d33] ftdi: A few errors are err() that should be debug 
 # good: [b5d674ab] 8250: remove a few inlines of dubious value

( but it's the same basic problem: we lost the lock init sequence when a
  patch was removed from the middle. )

	Ingo

----------------->
>From b15be1e63d0df3a1b4a25e7a28cfca9f93690884 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Tue, 14 Oct 2008 12:14:17 +0200
Subject: [PATCH] serial: fix serial port lock init

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 drivers/serial/8250.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index d4104a3..d3ca7d3 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -2969,6 +2969,9 @@ static int __init serial8250_init(void)
 		"%d ports, IRQ sharing %sabled\n", nr_uarts,
 		share_irqs ? "en" : "dis");
 
+	for (i = 0; i < NR_IRQS; i++)
+		spin_lock_init(&irq_lists[i].lock);
+
 #ifdef CONFIG_SPARC
 	ret = sunserial_register_minors(&serial8250_reg, UART_NR);
 #else