ssert_spin_locked() is a better option.
Unless there's a bug, assert_spin_locked() is just going to incur an unnecessary cost every time it is called at runtime. My suggestion was to limit that check only to debugging kernels that include enabling lockdep when tracking down problems rather than needlessly evaluating the conditional every time when there are no bugs.
My experience with gpu drivers (i915) has been that hw and the software running it is varied enough that almost always it's better to unconditionally enable this stuff. I much prefer assert_spin_locked and friends over the lockdep versions since enabling full lockdep is not something you usually do. Especially not normal users, and we rely upon them for testing the old stuff. Furthermore for the modeset code the overhead is totally irrelevant since we're doing metric piles of register reads and writes in there anyway.
Did anything translate into an R-b here?
Dave.