[PATCH] drm: Do not use BUG_ON(!spin_is_locked())

[David Rientjes]

On Sun, 10 Aug 2014, Guenter Roeck wrote:

> spin_is_locked() always returns false in uniprocessor configurations
> and can therefore not be used with BUG_ON. Replace it with
> assert_spin_locked(), which exists for that very purpose.
> 

It may be helpful to assess whether any of these sites should be converted 
to lockdep_assert_held() so they have no cost when lockdep isn't enabled 
but still reveal problems when debugging.