6914050: jvm assertion "guard pages must be in use" in -Xcomp mode Summary: Move creating stack guard pages in jni attach thread before potential java call rather than after. Also cleanup stack guard pages when jni attach fails Reviewed-by: never, dholmes

6910182: CMS: assert(_cursor[j] == _survivor_plab_array[j].end(),"Ctl pt invariant") Summary: Calculation of the slicing of survivor spaces for MT was incorrect. Reviewed-by: ysr