Mutex & Sync, A note for myself

- Mutex(actually, atomicity) & Sync complement each other (within the same boundary: either global or local)
- All mutex/sync tools (mutex, atomic claim, lock, semaphore, fence, barrier) have the same (simulation) power, and thus, CANNOT be built(simulated) without the hardware intrinsic atomicity.
- All sync can be simulated by async software model, but NO sync can be done(simulated) without the hardware intrinsic sync. Eg: the read, write ops; the "2-state lovers" problem.
* At the deepest meaning leavel, mutex/sync is only needed for INFORMATION RESERVATION!