  We study the variation of the massive black hole in both normal and extended
thermodynamic phase spaces via two methods. The first method includes a charged
particle absorbed by the black hole, while the second method includes a shell
of dust falling into the black hole. Using the former method, the first and
second laws of thermodynamics are always satisfied in the normal phase space,
while in the extended phase space, the first law of thermodynamics is also
satisfied, but the validity of the second law of thermodynamics depends on the
model parameters. Applying the latter method, the first and second laws of
thermodynamics are both valid. We argue that the possible reason for the
violation of the second law of thermodynamics via the former method may be
attributed to the assumption that the change of internal energy of the black
hole is equal to the energy of the particle. Finally, we show that the event
horizon always exists to guarantee the validity of the weak cosmic censorship
in both phase spaces, which means that the violation of the second law of
thermodynamics under the assumption does not affect the weak cosmic censorship
conjecture. This further supports our argument that the assumption in the first
method may be the reason for the violation of the law and it requires deeper
treatment.
