[media] saa7146: replace current->state by set_current_state()

Use helper functions to access current->state.
Direct assignments are prone to races and therefore buggy.

current->state = TASK_RUNNING can be replaced by __set_current_state()

Thanks to Peter Zijlstra for the exact definition of the problem.
Suggested-By: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/common/saa7146/saa7146_vbi.c

@@ -95,7 +95,7 @@ static int vbi_workaround(struct saa7146_dev *dev)
 
 		/* prepare to wait to be woken up by the irq-handler */
 		add_wait_queue(&vv->vbi_wq, &wait);
-		current->state = TASK_INTERRUPTIBLE;
+		set_current_state(TASK_INTERRUPTIBLE);
 
 		/* start rps1 to enable workaround */
 		saa7146_write(dev, RPS_ADDR1, dev->d_rps1.dma_handle);
@@ -106,7 +106,7 @@ static int vbi_workaround(struct saa7146_dev *dev)
 		DEB_VBI("brs bug workaround %d/1\n", i);
 
 		remove_wait_queue(&vv->vbi_wq, &wait);
-		current->state = TASK_RUNNING;
+		__set_current_state(TASK_RUNNING);
 
 		/* disable rps1 irqs */
 		SAA7146_IER_DISABLE(dev,MASK_28);