进程同步相关术语解释
Race Condition: A situation where
1. serveral processes access and manipulate the same data concurrently
2.the outcome of the execution depends on the particular order in which the access takes place


Critical Section: a segment of code
If process p1 is executing in its critical section, then no other processes can be executing in their critical sections


Semaphore: a syncrhonization tool
A semaphore contains an integer variable is accessed only through two standard operations: acquire() and release()

            Semaphore sem = new Semaphore(1);        sem.acquire();            //critical section        sem.release();            //remainder section    

Spinlock (自旋锁): 是一种Semaphore，它能造成一种情形：
一个进程由于等待锁而不停地空转。这个空转的感觉就像在"spin"(自旋)
由于自旋时进程仍处于运行态，所以很浪费CPU.


Deadlock: a situation where
two or more processes are waiting indefinitel for an event that can be caused by one of the waiting processes.


Starvation, or Infinite Blocking:
1. 一种状况：进程永远获取不到锁
2. 如果锁的等待队列采取LIFO模式，就会靠成这种状况