Linux线程同步互斥量

g++编译时需要g++ my.cpp -pthread

#include <pthread.h>
#include <semaphore.h>
int num1 = 0;
sem_t sem1;
sem_t sem2;

void* pthread_inc1(void* p)
{
    for (int i = 0; i < 100000; i++) {
        sem_wait(&sem2);//当信号量信号量是0时会阻塞,大于0则会通过,并将信号量减1
        num1++;
        sem_post(&sem1); //使信号量+1
    }
    return NULL;
}
void* pthread_dec1(void* p)
{
    for (int i = 0; i < 100000; i++) {        
        sem_wait(&sem1);//
        num1--;
        sem_post(&sem2);
    }
    return NULL;
}
int int() {
    sem_init(&sem1, 0, 0);//参数三设置开始状态0
    sem_init(&sem2, 0, 1);//参数三设置开始状态为1,参数三能一定程度上影响线程开始
    pthread_t pid[50];
    for (int i = 0; i < 50; i++) {
        if (i % 2) pthread_create(&pid[i], NULL, pthread_inc1,NULL);
        else   pthread_create(&pid[i], NULL, pthread_dec1, NULL);
    }
    for (int i = 0; i < 50; i++) {
        pthread_join(pid[i], NULL);
    }
    std::cout << num1 << std::endl;
    sem_destroy(&sem1);
    sem_destroy(&sem2);
    return 0;
}