  We use the Kruskal time coordinate T to define the initial time. By this way,
it naturally divides the stable study into one connected with the two regions:
the white-hole-connected region and the black-hole-connected region. The union
of the two regions covers the Schwarzschild space-time (r>2m). We also obtain
the very reasonable conclusion: the white-hole-connected region is instable;
whereas the black-hole-connected region is stable. If we take the instability
with caution and seriousness, it might be not unreasonable to regard that the
Schwarzschild black hole might be instable too.
