each process runs in its private space.A process running in User Mode
refers to private stack,data and code areas. When running in Kernel
Mode,the process addresses the kernel data and code areas and uses
another private stack.

Because the kenel is reentrant,several kernel contral paths-----each
related to a different process---may be executed in turn.

i can't understand the key "different" from above "how can several
kernel contral paths related to a different process."