Positive and non-negative sectional curvature of semi-riemannian metrics

I am currently studying the techniques related to geometry of positive and non-negative sectional curvature of Riemannian metrics. In particular, I have done some work with Cheeger deformations. I started to wonder:

On the context of semi-Riemannian metrics, is there restrictive conditions for positive and non-negative sectional curvature? (I know that there are restrictions on defining sectional curvature on this context, since there are degenerated planes, I am wondering about sectional curvature where it is well defined).

It seems to me that is rather delicate how to work with isometries groups of semi-Riemannian metrics and their actions. Is there any hope that the standard techniques of Cheeger deformations apply with small modifications on this context, considering the validity of the first question?