From: Mika Westerberg <mika.westerberg@linux.intel.com>
Date: Thu, 23 Jun 2011 12:39:00 +0000 (+0100)
Subject: serial: mrst_max3110: initialize waitqueue earlier
X-Git-Tag: MMI-PSA29.97-13-9~19118
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=33b1e6939f5c37ab8e64280fd3d54046607b5c80;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git

serial: mrst_max3110: initialize waitqueue earlier

The driver went to initialize its waitqueue at the start of the main
processing thread.  However, it is possible that this thread is not
scheduled on a CPU before the write function is called which leads to a
following error:

  BUG: spinlock bad magic on CPU#1, swapper/1
   lock: f5f3ebdc, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
  Pid: 1, comm: swapper Not tainted 3.0.0-rc2+ #67
  Call Trace:
   [<c1289663>] spin_bug+0xa3/0xf0
   [<c12897ad>] do_raw_spin_lock+0x7d/0x150
   [<c14963de>] _raw_spin_lock_irqsave+0x4e/0x60
   [<c102f2bb>] __wake_up+0x1b/0x50
   [<c12d3715>] serial_m3110_con_write+0x55/0x60
   [<c1041575>] __call_console_drivers+0x75/0x90
   [<c10415d9>] _call_console_drivers+0x49/0x80
   [<c1041baa>] console_unlock+0xca/0x1f0
   [<c10420ef>] vprintk+0x18f/0x4f0
   [<c14928a3>] printk+0x18/0x1a
   [<c1042730>] register_console+0x2e0/0x350
   [<c12d098e>] uart_add_one_port+0x33e/0x3d0
   [<c1485ba6>] serial_m3110_probe+0x1c2/0x1df
   [<c1303db7>] spi_drv_probe+0x17/0x20
   ...

Fix this by initializing the waitqueue before the main thread is
created.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/drivers/tty/serial/mrst_max3110.c b/drivers/tty/serial/mrst_max3110.c
index 3be1b0dd6f22..a764bf99743b 100644
--- a/drivers/tty/serial/mrst_max3110.c
+++ b/drivers/tty/serial/mrst_max3110.c
@@ -421,7 +421,6 @@ static int max3110_main_thread(void *_max)
 	int ret = 0;
 	struct circ_buf *xmit = &max->con_xmit;
 
-	init_waitqueue_head(wq);
 	pr_info(PR_FMT "start main thread\n");
 
 	do {
@@ -838,6 +837,8 @@ static int __devinit serial_m3110_probe(struct spi_device *spi)
 	max->con_xmit.head = 0;
 	max->con_xmit.tail = 0;
 
+	init_waitqueue_head(&max->wq);
+
 	max->main_thread = kthread_run(max3110_main_thread,
 					max, "max3110_main");
 	if (IS_ERR(max->main_thread)) {