USB: fix spinlock recursion in cdc-acm.c

this fixes the spinlock recursion issue. The older fix was incomplete.


Signed-off-by: Oliver Neukum <[e-mail]>
Acked-by: Pete Zaitcev <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/class/cdc-acm.c

···
 	if (!ACM_READY(acm))
 		return;
 
-	spin_lock(&acm->throttle_lock);
+	spin_lock_irqsave(&acm->throttle_lock, flags);
 	throttled = acm->throttle;
-	spin_unlock(&acm->throttle_lock);
+	spin_unlock_irqrestore(&acm->throttle_lock, flags);
 	if (throttled)
 		return;
 
···
 	dbg("acm_rx_tasklet: procesing buf 0x%p, size = %d", buf, buf->size);
 
 	tty_buffer_request_room(tty, buf->size);
-	spin_lock(&acm->throttle_lock);
+	spin_lock_irqsave(&acm->throttle_lock, flags);
 	throttled = acm->throttle;
-	spin_unlock(&acm->throttle_lock);
+	spin_unlock_irqrestore(&acm->throttle_lock, flags);
 	if (!throttled)
 		tty_insert_flip_string(tty, buf->base, buf->size);
 	tty_flip_buffer_push(tty);