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
  [<c1490006>] ? init_idle+0x8d/0x20c
  [<c14963de>] _raw_spin_lock_irqsave+0x4e/0x60
  [<c102f2bb>] ? __wake_up+0x1b/0x50
  [<c102f2bb>] __wake_up+0x1b/0x50
  [<c12d03bc>] ? uart_console_write+0x4c/0x60
  [<c12d36c0>] ? serial_m3110_enable_ms+0x10/0x10
  [<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
  [<c10787cb>] ? trace_hardirqs_on+0xb/0x10
  [<c14928a3>] printk+0x18/0x1a
  [<c1042730>] register_console+0x2e0/0x350
  [<c12d098e>] uart_add_one_port+0x33e/0x3d0
  [<c10787cb>] ? trace_hardirqs_on+0xb/0x10
  [<c103e10b>] ? try_to_wake_up+0x18b/0x250
  [<c1485ba6>] serial_m3110_probe+0x1c2/0x1df
  [<c12d3d20>] ? serial_m3110_suspend+0x40/0x40
  [<c1303db7>] spi_drv_probe+0x17/0x20
  ...

We 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: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 1 deletions

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)) {