线程同步机制之自旋锁

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>

/* 定义变量 */
pthread_spinlock_t spin;

/*定义全局变量*/
int i = 0;

/* 线程函数 */
void *thread_fun(void *arg)
{
    int ret = 0;
    int x = 0;
    pthread_spin_lock(&spin);
    ret = pthread_spin_trylock(&spin);//已经上锁了，再调用该函数时，会立即返回错误
    printf("ret = %dn", ret);
    for(x = 0; x < 10000000; x++)
    {
        i++;
    }
    pthread_spin_unlock(&spin);
    //pthread_spin_trylock(&spin);
    return NULL;
}

int main(void)
{
    pthread_t tid;

    /*自选锁初始化*/
    pthread_spin_init(&spin, PTHREAD_PROCESS_PRIVATE);

    /* 创建一个线程 */
    if (pthread_create(&tid, NULL, thread_fun, NULL)== -1)
         printf("pthread_create()");

    pthread_join(tid, NULL);


    pthread_spin_lock(&spin);
    printf("i = %dn",i);
    pthread_spin_unlock(&spin);
    
    pthread_spin_destroy(&spin);
    return 0;
}

/*
int pthread_spin_init(pthread_spinlock_t *lock,int pshared);
int pthread_spin_destroy(pthread_spinlock_t *lock)
int pthread_spin_lock(pthread_spinlock_t *lock)
int pthread_spin_trylock(pthread_spinlock_t *lock)//该函数不能自旋
int pthread_spin_unlock(pthread_spinlock_t *lock)

成功返回0，失败返回错误编号，

PTHREAD_PROCESS_PRIVATE

/*gcc pthread_spin.c -o spin -lpthread*/