操作系统信号量PV经典问题：沉睡的理发师

#include<iostream> #include<windows.h> #include<cstdio> using namespace std; int waiting=0; int chairs=2; //为了使结果便于观测仅采用2个等待椅 #define random (rand()*10000)/RAND_MAX //产生一个随机数代表顾客在时间上随机进入理发店 DWORD a; HANDLE barbers=CreateSemaphore(NULL,1,1,"barbers"); HANDLE customers=CreateSemaphore(NULL,0,1,"customers"); HANDLE mutex=CreateMutex(NULL,FALSE,"mutex"); //理发师开始为一个顾客理发 void cut_hair() { Sleep(10); cout<<"Barber working."<<endl; Sleep(10000); } //一个顾客理完发并离开 void get_haircut() { Sleep(10000); cout<<"One custmer finished"<<endl; } DWORD WINAPI ThreadCustomer(LPVOID lpParam) { WaitForSingleObject(mutex,INFINITE); cout<<"One custmer enter."<<endl; if(waiting<chairs) { cout<<"Still have seats. waiting."<<endl; waiting++; ReleaseSemaphore(customers,1,NULL); ResumeThread(customers);\ ReleaseMutex(mutex); WaitForSingleObject(barbers,INFINITE); cout<<endl<<endl; get_haircut(); } else { cout<<"Full, the custmer left"<<endl; ReleaseMutex(mutex); } return 0; } DWORD WINAPI ThreadBarber(LPVOID lpParam) { while(true) { WaitForSingleObject(customers,INFINITE); WaitForSingleObject(mutex,INFINITE); waiting--; ReleaseSemaphore(barbers,1,NULL); ResumeThread(barbers); ReleaseMutex(mutex); cut_hair(); } return 0; } int main() { HANDLE customerThread; HANDLE barberThread=CreateThread(NULL,0,ThreadBarber,NULL,0,NULL); while(true) { Sleep(random); cout<<endl; customerThread=CreateThread(NULL,0,ThreadCustomer,NULL,a,NULL); cout<<endl; } return 0; }