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【Linux】Mutex互斥量线程同步的例子
0、互斥量
Windows下的互斥量
是个内核对象，每次WaitForSingleObject和ReleaseMutex时都会检查当前线程ID和占有互斥量的线程ID是否一致。
当多次Wait**时就要对应多次ReleaseMutex， 当ReleaseMutex过多次数时如果发现当前占有互斥量的线程ID和当前调用ReleaseMutex的线程ID不一致时仅仅返回FLASE，GetLastError返回ERROR_NOT_OWNER，没有其他副作用。
当占有mutex的线程在Release之前退出时，该mutex被【遗弃】，此时系统自动收回mutex，可供其他线程申请。
允许多次等待
WaitForSingleObject(hMutex, time);
WaitForSingleObject(hMutex, itme);
多次等待 对应多次释放
ReleaseMutex(hMutex);
ReleaseMutex(hMutex);
Linux下的互斥量
可以设置互斥量的属性是否为可以被同一个线程多次lock， 还可以设置该互斥量的范围，即是用于进程之间同步 还是 同一进程不同线程之间的同步。
相关API 将说明见代码注释部分。
1、相关API
//Initialize a mutex with attribute(can be NULL) int pthread_mutex_init( pthread_mutex_t* mutex, const pthread_mutexattr_t* mutexattr); //lock a mutex int pthread_mutex_lock(pthread_mutex_t* mutex); //ulock a mutex int pthread_mutex_unlock(pthread_mutex_t* mutex); //destroy a mutex int pthread_mutex_destroy(pthread_mutex_t* mutex); int pthread_mutexattr_setpshared( pthread_mutexattr_t* mattr, int pshared //PTHREAD_PROCESS_SHARE | PTHREAD_PROCESS_PRIVATE ); int pthread_mutexattr_getshared( pthread_mutexattr_t* mattr, int* pshared); int pthread_mutexattr_settype( pthread_mutexattr_t* attr, int type //PTHREAD_MUTEX_TIMED_NP -- default value //PTHREAD_MUTEX_RECURISIVE_NP -- allow a thread lock multitimes //PTHREAD_MUTEX_ERRORCHECK_NO -- check error lock, return EDEADLK if the same thread want to LOCK //PTHREAD_MUTEX_ADAPTIVE_NO -- adaptive lock, the simplest lock ) int pthread_mutexattr_gettype( pthread_mutexattr_t* attr, int* type )
2、demo
#include <iostream>#include <pthread.h>#include <unistd.h>#include <errno.h>using namespace std;/*********************************************** * * Initialize a mutex with attribute(can be NULL) * int pthread_mutex_init( * pthread_mutex_t* mutex, * const pthread_mutexattr_t* mutexattr); * * lock a mutex * int pthread_mutex_lock(pthread_mutex_t* mutex); * * unlock a mutex * int pthread_mutex_unlock(pthread_mutex_t* mutex); * * destroy a mutex * int pthread_mutex_destroy(pthread_mutex_t* mutex); * * int pthread_mutexattr_setpshared( * pthread_mutexattr_t* mattr, * int pshared //PTHREAD_PROCESS_SHARE | PTHREAD_PROCESS_PRIVATE * ); * * int pthread_mutexattr_getshared( * pthread_mutexattr_t* mattr, * int* pshared); * * int pthread_mutexattr_settype( * pthread_mutexattr_t* attr, * int type //PTHREAD_MUTEX_TIMED_NP -- default value * //PTHREAD_MUTEX_RECURISIVE_NP -- allow a thread lock multitimes * //PTHREAD_MUTEX_ERRORCHECK_NO -- check error lock, return EDEADLK if the same thread want to LOCK * //PTHREAD_MUTEX_ADAPTIVE_NO -- adaptive lock, the simplest lock * ) * * * int pthread_mutexattr_gettype( * pthread_mutexattr_t* attr, * int* type * ) * *********************************************/void* work_thread(void* p){ if (NULL == p) return const_cast<char*>("invalid thread argument"); pthread_mutex_t* pMutex = (pthread_mutex_t*)(p); //current thread ID pthread_t nThreadID = pthread_self(); int i = 0; while(++ i <= 3) { //lock multi times pthread_mutex_lock(pMutex); pthread_mutex_lock(pMutex); cout << "Thread " << nThreadID << " is Running! " << endl; //and so unlock multi times pthread_mutex_unlock(pMutex); pthread_mutex_unlock(pMutex); usleep(1000 * 1); //1 miliseconds } return const_cast<char*>("------ finish -----------");}void* work_thread2(void* p){ if (NULL == p) return const_cast<char*>("invalid thread argument"); pthread_mutex_t* pMutex = (pthread_mutex_t*)(p); //current thread ID pthread_t nThreadID = pthread_self(); int i = 0; while(++ i <= 3) { //if current thread can not enter mutex, //and the function pthread_mutex_trylock will RETURN Immediatly if ( EBUSY == pthread_mutex_trylock(pMutex)) cout << "Other thread is lock the resouce, i am waiting.." << endl; else { cout << "Thread " << nThreadID << " is Running! " << endl; pthread_mutex_unlock(pMutex); usleep(1000 * 1); //1 miliseconds } } return const_cast<char*>("------ finish -----------");}int main(){ const size_t nThreadCount = 3; pthread_t threadIDs[nThreadCount]; int nRet = -1; pthread_mutex_t mutex; pthread_mutexattr_t mutexattr; void* pRet = NULL; //thread return value //allow a thread lock multi times nRet = pthread_mutexattr_settype(&mutexattr, PTHREAD_MUTEX_RECURSIVE_NP); nRet = pthread_mutex_init(&mutex, &mutexattr); if (0 != nRet) return -1; for (size_t i = 0; i < nThreadCount - 1; ++ i) { nRet = pthread_create(&threadIDs[i], NULL, work_thread, (void*)(&mutex)); if (0 != nRet) continue; } nRet = pthread_create(&threadIDs[nThreadCount - 1], NULL, work_thread2, (void*)(&mutex)); if (0 != nRet) cerr << endl << "work_thread2 created falied! " << endl; for (size_t i = 0; i < nThreadCount; ++ i) { nRet = pthread_join(threadIDs[i], &pRet); if (0 == nRet) { cout << " Thread " << threadIDs[i] << " Finished ! " " It‘s return value is " << (char*)pRet << endl; } } pthread_mutex_destroy(&mutex); return 0;}
3、执行结果
【Linux】Mutex互斥量线程同步的例子
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