wan: cosa: 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 is 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>
Acked-By: Jan "Yenya" Kasprzak <kas@fi.muni.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/cosa.c

@@ -806,21 +806,21 @@ static ssize_t cosa_read(struct file *file,
 	spin_lock_irqsave(&cosa->lock, flags);
 	add_wait_queue(&chan->rxwaitq, &wait);
 	while (!chan->rx_status) {
-		current->state = TASK_INTERRUPTIBLE;
+		set_current_state(TASK_INTERRUPTIBLE);
 		spin_unlock_irqrestore(&cosa->lock, flags);
 		schedule();
 		spin_lock_irqsave(&cosa->lock, flags);
 		if (signal_pending(current) && chan->rx_status == 0) {
 			chan->rx_status = 1;
 			remove_wait_queue(&chan->rxwaitq, &wait);
-			current->state = TASK_RUNNING;
+			__set_current_state(TASK_RUNNING);
 			spin_unlock_irqrestore(&cosa->lock, flags);
 			mutex_unlock(&chan->rlock);
 			return -ERESTARTSYS;
 		}
 	}
 	remove_wait_queue(&chan->rxwaitq, &wait);
-	current->state = TASK_RUNNING;
+	__set_current_state(TASK_RUNNING);
 	kbuf = chan->rxdata;
 	count = chan->rxsize;
 	spin_unlock_irqrestore(&cosa->lock, flags);
@@ -890,14 +890,14 @@ static ssize_t cosa_write(struct file *file,
 	spin_lock_irqsave(&cosa->lock, flags);
 	add_wait_queue(&chan->txwaitq, &wait);
 	while (!chan->tx_status) {
-		current->state = TASK_INTERRUPTIBLE;
+		set_current_state(TASK_INTERRUPTIBLE);
 		spin_unlock_irqrestore(&cosa->lock, flags);
 		schedule();
 		spin_lock_irqsave(&cosa->lock, flags);
 		if (signal_pending(current) && chan->tx_status == 0) {
 			chan->tx_status = 1;
 			remove_wait_queue(&chan->txwaitq, &wait);
-			current->state = TASK_RUNNING;
+			__set_current_state(TASK_RUNNING);
 			chan->tx_status = 1;
 			spin_unlock_irqrestore(&cosa->lock, flags);
 			up(&chan->wsem);
@@ -905,7 +905,7 @@ static ssize_t cosa_write(struct file *file,
 		}
 	}
 	remove_wait_queue(&chan->txwaitq, &wait);
-	current->state = TASK_RUNNING;
+	__set_current_state(TASK_RUNNING);
 	up(&chan->wsem);
 	spin_unlock_irqrestore(&cosa->lock, flags);
 	kfree(kbuf);