详解Linux多线程中互斥锁、读写锁、自旋锁、条件变量、信号量

对互斥锁进行加锁后，任何其他试图再次对互斥锁加锁的线程将会被阻塞，直到锁被释放

#include 
#include 
#include 
#include 
#include 

 char *pTestBuf = nullptr; // 全局变量

 /* 定义互斥锁 */
pthread_mutex_t mutex;

void *ThrTestMutex(void *p)
{
    pthread_mutex_lock(&mutex);     // 加锁
    {
        pTestBuf = (char*)p;
        sleep(1);
    }
    pthread_mutex_unlock(&mutex);   // 解锁
}

int main()
{   
    /* 初始化互斥量, 默认属性 */
    pthread_mutex_init(&mutex, NULL);

    /* 创建两个线程对共享资源访问 */
    pthread_t tid1, tid2;
    pthread_create(&tid1, NULL, ThrTestMutex, (void *)"Thread1");
    pthread_create(&tid2, NULL, ThrTestMutex, (void *)"Thread2"); 

    /* 等待线程结束 */
    pthread_join(tid1, NULL);
    pthread_join(tid2, NULL); 

    /* 销毁互斥锁 */
    pthread_mutex_destroy(&mutex);  

    return 0;
}

    #include 
    int phtread_rwlock_init(pthread_rwlock_t *restrict rwlock, const pthread_rwlockattr_t *restrict attr);
    int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);

    #include 
    /** 加读锁 */
    int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);
    /** 加写锁 */
    int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);
    /** 释放锁 */
    int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);

#include 
#include 
#include 
#include 
#include 

/* 定义读写锁 */
pthread_rwlock_t rwlock;

/* 定义共享资源变量 */
int g_nNum = 0;

/* 读操作 其他线程允许读操作 不允许写操作 */
void *fun1(void *arg)  
{  
    while(1)  
    {  
        pthread_rwlock_rdlock(&rwlock);  
        {
            printf("read thread 1 == %d
", g_nNum);
        }      
        pthread_rwlock_unlock(&rwlock);

        sleep(1);
    }
}  

/* 读操作，其他线程允许读操作，不允许写操作 */
void *fun2(void *arg)
{    
    while(1)
    {
        pthread_rwlock_rdlock(&rwlock);  
        {
            printf("read thread 2 == %d
", g_nNum);
        }      
        pthread_rwlock_unlock(&rwlock);

        sleep(1);
    }
} 

/* 写操作，其它线程都不允许读或写操作 */
void *fun3(void *arg)
{    
    while(1)
    {
        pthread_rwlock_wrlock(&rwlock);
        {
            g_nNum++;        
            printf("write thread 1
");
        }
        pthread_rwlock_unlock(&rwlock);
        sleep(1);
    }
} 
/* 写操作，其它线程都不允许读或写操作 */ 
void *fun4(void *arg)
{    
    while(1)
    {  
        pthread_rwlock_wrlock(&rwlock);  
        {
            g_nNum++;  
            printf("write thread 2
");  
        }
        pthread_rwlock_unlock(&rwlock); 

        sleep(1);  
    }  
}  
  
int main(int arc, char *argv[])  
{  
    pthread_t ThrId1, ThrId2, ThrId3, ThrId4;  
      
    pthread_rwlock_init(&rwlock, NULL);  // 初始化一个读写锁  
      
    /* 创建测试线程 */
    pthread_create(&ThrId1, NULL, fun1, NULL);  
    pthread_create(&ThrId2, NULL, fun2, NULL);  
    pthread_create(&ThrId3, NULL, fun3, NULL);  
    pthread_create(&ThrId4, NULL, fun4, NULL);  
      
    /* 等待线程结束，回收其资源 */
    pthread_join(ThrId1, NULL);  
    pthread_join(ThrId2, NULL);  
    pthread_join(ThrId3, NULL);  
    pthread_join(ThrId4, NULL);  
      
    pthread_rwlock_destroy(&rwlock);      // 销毁读写锁  
      
    return 0;  
}

    include
    spinlock_t lock;      //定义自旋锁
    spin_lock_init(&lock);   //初始化自旋锁
    spin_lock(&lock);      //获得锁，如果没获得成功则一直等待
    {
        .......         //处理临界资源
    }
    spin_unlock(&lock);     //释放自旋锁

#include   
#include   
#include   
#include  

pthread_cond_t taxicond = PTHREAD_COND_INITIALIZER;  
pthread_mutex_t taximutex = PTHREAD_MUTEX_INITIALIZER;  
  
void *ThrFun1(void *name)  
{  
    char *p = (char *)name;  
    
    // 加锁，把信号量加入队列，释放信号量
    pthread_mutex_lock(&taximutex); 
    {
        pthread_cond_wait(&taxicond, &taximutex);  
    } 
    pthread_mutex_unlock(&taximutex);  

    printf ("ThrFun1: %s now got a signal!
", p);  
    pthread_exit(NULL);  
}  
  
void *ThrFun2(void *name)  
{  
    char *p = (char *)name;  
    printf ("ThrFun2: %s cond signal.
", p);    // 发信号
    pthread_cond_signal(&taxicond);  
    pthread_exit(NULL);  
}  
  
int main (int argc, char **argv)  
{  
    pthread_t Thread1, Thread2;  
    pthread_attr_t threadattr;
    pthread_attr_init(&threadattr);  // 线程属性初始化
  
    // 创建三个线程 
    pthread_create(&Thread1, &threadattr, ThrFun1, (void *)"Thread1");  
    sleep(1);  

    pthread_create(&Thread2, &threadattr, ThrFun2, (void *)"Thread2");  
    sleep(1);   

    pthread_join(Thread1, NULL);
    pthread_join(Thread2, NULL);
  
    return 0;  
}

    pthread_mutex_lock(&taximutex); 
    {
        while(value != wantValue)
        {
            pthread_cond_wait(&taxicond, &taximutex);  
        }
    } 
    pthread_mutex_unlock(&taximutex); 

#include 

// 初始化信号量
int sem_init(sem_t *sem, int pshared, unsigned int value);

// 信号量P操作（减 1）
int sem_wait(sem_t *sem);

// 以非阻塞的方式来对信号量进行减1操作
int sem_trywait(sem_t *sem);

// 信号量V操作（加 1）
int sem_post(sem_t *sem);

// 获取信号量的值
int sem_getvalue(sem_t *sem, int *sval);

// 销毁信号量
int sem_destroy(sem_t *sem);

// 信号量用于同步实例
#include 
#include 
#include 
#include 

sem_t sem_g,sem_p;   //定义两个信号量
char s8Test = 'a'; 

void *pthread_g(void *arg)  //此线程改变字符的值
{    
    while(1)
    {
        sem_wait(&sem_g);
        s8Test++;
        sleep(2);
        sem_post(&sem_p);
    }
} 
void *pthread_p(void *arg)  //此线程打印字符的值
{    
    while(1)
    {
        sem_wait(&sem_p);        
        printf("%c",s8Test);
        fflush(stdout);
        sem_post(&sem_g);
    }
} 
int main(int argc, char *argv[])
{    
    pthread_t tid1,tid2;
    sem_init(&sem_g, 0, 0); // 初始化信号量为0
    sem_init(&sem_p, 0, 1); // 初始化信号量为1
    
    pthread_create(&tid1, NULL, pthread_g, NULL);
    pthread_create(&tid2, NULL, pthread_p, NULL); 

    pthread_join(tid1, NULL);
    pthread_join(tid2, NULL);    
    return 0;
}