nAdvantages
uThread switching does not involve the kernel: no mode
switching
uScheduling can be application specific: choose the best algorithm.
uULTs can run on any OS. Only needs a thread library
nInconveniences
uMost system calls are blocking and the kernel blocks processes.
So all
threads within the process will be blocked
uThe kernel can only assign processes to processors. Two threads within
the same
process cannot run simultaneously on two processors