nachos线程与同步

#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; };