synch-sem.h

nachos下线程与同步的实验

#include "copyright.h"
#include "thread.h"
#include "list.h"

class Semaphore
{
      public:
             Semaphore(char* debugName, int initialValue); //设置信号量初值
             ~Semaphore();  //析构函数
             char* getName() { return name; }  //debugging assist
             
             void P();  //waits until value > 0, then decrement
             void V();  //increment, waking up a thread waiting in P() if necessary
                        //均为原子操作   
      private:
              char *name;   //useful for debugging
              int value;    //信号量的值，均为非负的 
              List *queue;  //threads waiting in P() for the value to be >0 
};

class Lock
{
      public:
             Lock(char* debugName);  //initialize lock to be FREE
             ~Lock();  //析构函数
             char* getName() { return name; } //debugging assist
             
             void Acquire();  //wait until the lock is FREE, then set it to BUSY
             void Release();  //set lock to be FREE, waking up a thread waiting
                              //均为原子操作
             
             bool isHeldByCurrentThread();  // true if the current thread
             // holds this lock.  Useful for checking in Release, and in
             // Condition variable ops below.
             
      private:
              char* name;  //for debugging
              Thread *HoldThread;
              bool Hold;
              Semaphore *semaphore;
              int threadnum;
};

class Condition
{
      public:
             Condition(char* debugName); //初始化条件变量为"no one waiting"
             ~Condition();  //析构函数
             char* getName() { return name; }  //debugging assist
             
             void Wait(Lock *conditionLock); //release the lock, relinquish the CPU until signaled,
                                             //then re-acquire the lock
                                             //为原子操作
                                             
             void Signal(Lock *conditionLock); //wake up a thread, 
                                               //if there are any waiting on the condition
             
             void Broadcast(Lock *conditionLock); 
             //wake up all threads waiting on the condition
             
      private:
              char* name;
              Semaphore *semaphore;
              int threadnum;
};