input: replace spin_lock_bh with spin_lock_irqsave in ml_ff_playback

ml_ff_playback() uses spin_(un)lock_bh. However this function is called
with interrupts disabled from erase_effect() in drivers/input/ff-core.c:196.

This is not permitted, and will result in a WARN_ON in the bottom half handling code.
This patch changes this function to just use spin_lock_irqsave() instead, solving
the problem and simplifying the locking logic.

This was reported as entry #106559 in kerneloops.org

Reported-by: kerneloops.org
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/input/ff-memless.c

@@ -397,8 +397,9 @@ static int ml_ff_playback(struct input_dev *dev, int effect_id, int value)
 {
 	struct ml_device *ml = dev->ff->private;
 	struct ml_effect_state *state = &ml->states[effect_id];
+	unsigned long flags;
 
-	spin_lock_bh(&ml->timer_lock);
+	spin_lock_irqsave(&ml->timer_lock, flags);
 
 	if (value > 0) {
 		debug("initiated play");
@@ -424,7 +425,7 @@ static int ml_ff_playback(struct input_dev *dev, int effect_id, int value)
 		ml_play_effects(ml);
 	}
 
-	spin_unlock_bh(&ml->timer_lock);
+	spin_unlock_irqrestore(&ml->timer_lock, flags);
 
 	return 0;
 }