Oscillatory Null Singularity inside Realistic Spinning Black Holes

We calculate the asymptotic behavior of the curvature scalar (Riemann${)}^2$ near the null weak singularity at the inner horizon of a generic spinning black hole, and show that this scalar oscillates an infinite number of times while diverging. The dominant parallel-propagated Riemann components oscillate in a similar manner. This oscillatory behavior, which is a remarkable contrast to the monotonic mass-inflation singularity in spherical charged black holes, is caused by the dragging of inertial frames due to the black hole's spin.