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【PTHREAD】线程互斥与同步之自旋锁

news 来源：原创 2024/5/5 11:12:54

1 自旋锁类型

typedef volatile int pthread_spinlock_t;

2 初始化与销毁自旋锁

int pthread_spin_init(pthread_spinlock_t *lock, int pshared);
int pthread_spin_destroy(pthread_spinlock_t *lock);

PTHREAD_PROCESS_PRIVATE
PTHREAD_PROCESS_SHARED

3 自旋锁的加锁解锁

int pthread_spin_lock(pthread_spinlock_t *lock);
int pthread_spin_trylock(pthread_spinlock_t *lock);
int pthread_spin_unlock(pthread_spinlock_t *lock);

4 案例：自旋锁的使用

源码

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <time.h>

pthread_spinlock_t spinlock;

void *start_routine_01(void *ptr)
{
    printf("子线程(%lu)开始运行...\n", pthread_self());
    for (size_t i = 0; i < 3; i++)
    {
        pthread_spin_lock(&spinlock);
        printf("子线程(%lu)进入自旋锁\n", pthread_self());
        sleep(1);
        printf("子线程(%lu)离开自旋锁\n", pthread_self());
        pthread_spin_unlock(&spinlock);
    }
    return (void*)"9999";
}

void *start_routine_02(void *ptr)
{
    printf("子线程(%lu)开始运行...\n", pthread_self());
    for (size_t i = 0; i < 3; i++)
    {
        pthread_spin_lock(&spinlock);
        printf("子线程(%lu)进入自旋锁\n", pthread_self());
        sleep(1);
        printf("子线程(%lu)离开自旋锁\n", pthread_self());
        pthread_spin_unlock(&spinlock);
    }
    return (void*)"9999";
}

int main(int argc, char const *argv[])
{
    printf("主线程(%lu)开始运行...\n", pthread_self());

    pthread_spin_init(&spinlock, PTHREAD_PROCESS_PRIVATE);
    
    pthread_t thread_id_01;
    pthread_create(&thread_id_01, NULL, start_routine_01, NULL);

    pthread_t thread_id_02;
    pthread_create(&thread_id_02, NULL, start_routine_02, NULL);

    pthread_join(thread_id_01, NULL);
    pthread_join(thread_id_02, NULL);

    pthread_spin_destroy(&spinlock);
    printf("主线程(%lu)即将退出...\n", pthread_self());
    exit(EXIT_SUCCESS);
}

输出

主线程(139684168165184)开始运行…
子线程(139684168161024)开始运行…
子线程(139684168161024)进入自旋锁
子线程(139684159768320)开始运行…
子线程(139684168161024)离开自旋锁
子线程(139684168161024)进入自旋锁
子线程(139684168161024)离开自旋锁
子线程(139684168161024)进入自旋锁
子线程(139684168161024)离开自旋锁
子线程(139684159768320)进入自旋锁
子线程(139684159768320)离开自旋锁
子线程(139684159768320)进入自旋锁
子线程(139684159768320)离开自旋锁
子线程(139684159768320)进入自旋锁
子线程(139684159768320)离开自旋锁
主线程(139684168165184)即将退出…