多线程互斥锁基本用法

1、关于互斥锁的函数

// 初始化互斥锁。attr 一般为 NULL
// 静态初始化：pthread_mutex_t mymutex= PTHREAD_MUTEX_INITIALIZER;
int pthread_mutex_init(pthread_mutex_t * mutex , pthread_mutexattr_t * attr);
// 销毁互斥锁
int pthread_mutex_destroy (pthread_mutex_t * mutex);
// 加锁 - 阻塞
int pthread_mutex_lock (pthread_mutex_t * mutex );
// 解锁
int pthread_mutex_unlock (pthread_mutex_t * mutex );
// 加锁 - 非阻塞
int pthread_mutex_trylock (pthread_mutex_t * mutex );

2、静态实现

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

void* test(void *arg)
{
    pthread_mutex_t *mutex = (pthread_mutex_t *)arg;

    printf("wait...\n");

    pthread_mutex_lock(mutex);  // 加锁

    printf("[test()] hello \n");

    pthread_mutex_unlock(mutex);  // 解锁

    pthread_exit((void *)0);
}

int main(void)
{
    pthread_t thread_id;

    // 静态分配：需要再声明的时候直接初始化，下面分开的做法是错误的
    // pthread_mutex_t mymutex;
    // mymutex= PTHREAD_MUTEX_INITIALIZER;
    pthread_mutex_t mymutex= PTHREAD_MUTEX_INITIALIZER;
    
    printf("[main()] main func !\n");
    
    pthread_mutex_lock(&mymutex);  // 加锁
    
    if (0 == pthread_create(&thread_id, NULL, (void *)test, (void *)(&mymutex))){
        printf("[main()] created thread~\n");
    }else{
        printf("[main()] create error\n");
    }
    
    sleep(1);
    
    printf("wait...\n");
    
    pthread_mutex_unlock(&mymutex);  // 解锁
    
    pthread_join(thread_id, NULL);   

    return 0;
}

输出如下，先创建线程，然后 wait，等 please wait... 完后主线程解锁，然后才 say hello：

[main()] main func !
[main()] created thread~
wait...
please wait...
[test()] hello 

3、动态实现，手动释放

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

void* test(void *arg)
{
    pthread_mutex_t *mutex = (pthread_mutex_t *)arg;
    
    printf("wait...\n");

    pthread_mutex_lock(mutex);

    printf("[test()] hello \n");

    pthread_mutex_unlock(mutex);

    pthread_exit((void *)0);
}

int main(void)
{
    pthread_t thread_id;

    pthread_mutex_t mymutex;
    
    // 动态分配：需要手动释放
    pthread_mutex_init(&mymutex, NULL);
    
    printf("[main()] main func !\n");
    
    pthread_mutex_lock(&mymutex);
    
    if (0 == pthread_create(&thread_id, NULL, (void *)test, (void *)(&mymutex))){
        printf("[main()] created thread~\n");
    }else{
        printf("[main()] create error\n");
    }
    
    sleep(1);
    
    printf("please wait...\n");
    
    pthread_mutex_unlock(&mymutex);
    
    pthread_join(thread_id, NULL);
    
    // 手动释放
    pthread_mutex_destroy(&mymutex);    
   
    return 0;
}

4、还有很多情况，后面再慢慢了解

还有死锁问题.

PTHREAD_MUTEX_INITIALIZER // 创建快速互斥锁。 

PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP // 创建递归互斥锁。

PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP // 创建检错互斥锁

[reference]
[1] wtz1985. linux多线程学习(四)——互斥锁线程控制[M]. (2009年01月17日 21:24:00). http://blog.csdn.net/wtz1985/article/details/3819052