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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>
This commit is contained in:
Mika Westerberg 2011-06-23 13:39:00 +01:00 committed by Linus Torvalds
parent 0bb04bf3df
commit 33b1e6939f
1 changed files with 2 additions and 1 deletions
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3
drivers/tty/serial/mrst_max3110.c
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@ -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)) {