linux 应用程序 mutex,Linux mutex 编程

最新推荐文章于 2025-05-08 14:40:38 发布

我爱专利

最新推荐文章于 2025-05-08 14:40:38 发布

阅读量282

点赞数

文章标签： linux 应用程序 mutex

本文通过三个示例展示了在多线程环境下，未使用、使用mutex以及使用std::lock_guard对共享资源进行读写操作的情况。未使用互斥锁时，结果不确定；引入互斥锁后，保证了读写的串行化，虽然程序运行速度变慢，但结果正确。使用std::lock_guard进一步简化了互斥锁的管理，确保了资源的安全访问。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

两个并行运行的程序片断，如线程，同时读写同一块内存，其结果是不确定的。这时候我们需要互斥锁，保证一个线程先读写完，然后另一个线程才可以读写。

1 没有使用mutex的例子

$ cat mutex-example-1.c

#include //ptrinf

#include //pthread_xxx

#include //sleep

int global_para = 0;

void *do_sth(void *p)

{

long i = (long)p;

printf("thread %d - start to read\n", i);

int temp = global_para;

sleep(2);

printf("thread %d - end of reading\n", i);

printf("thread %d - start to write\n", i);

sleep(2);

global_para = temp + (int)i;

printf("thread %d - end of reading\n", i);

}

int main()

{

pthread_t t1, t2;

pthread_create(&t1, 0, do_sth, (void *)1);

pthread_create(&t2, 0, do_sth, (void *)2);

pthread_join(t1, NULL);

pthread_join(t2, NULL);

printf("-- global_para is %d --\n", global_para);

}

# gcc mutex-example-1.c -o mutex-example-1 -lpthread && ./mutex-example-1

thread 2 - start to read

thread 1 - start to read

thread 1 - end of reading

thread 1 - start to write

thread 2 - end of reading

thread 2 - start to write

thread 1 - end of reading

thread 2 - end of reading

-- global_para is 2 --

每一次的运行结果都可能不一样。

$ gcc mutex-example-1.c -o mutex-example-1 -lpthread && ./mutex-example-1

thread 2 - start to read

thread 1 - start to read

thread 2 - end of reading

thread 2 - start to write

thread 1 - end of reading

thread 1 - start to write

thread 2 - end of reading

thread 1 - end of reading

-- global_para is 1 --

2 使用mutex的例子

$ cat mutex-example-2.c

#include //ptrinf,perror

#include //exit

#include //pthread_xxx

#include //sleep

int global_para = 0;

pthread_mutex_t lock;

void die(char *s)

{

perror(s);

exit(1);

}

void *do_sth(void *p)

{

long i = (long)p;

pthread_mutex_lock(&lock);

printf("thread %d - start to read\n", i);

int temp = global_para;

sleep(2);

printf("thread %d - end of reading\n", i);

printf("thread %d - start to write\n", i);

sleep(2);

global_para = temp + (int)i;

printf("thread %d - end of reading\n", i);

pthread_mutex_unlock(&lock);

}

int main()

{

pthread_t t1, t2;

if (pthread_mutex_init(&lock, NULL) != 0)

{

die("pthread_mutex_init()");

}

pthread_create(&t1, 0, do_sth, (void *)1);

pthread_create(&t2, 0, do_sth, (void *)2);

pthread_join(t1, NULL);

pthread_join(t2, NULL);

pthread_mutex_destroy(&lock);

printf("-- global_para is %d --\n", global_para);

}

$ gcc mutex-example-2.c -o mutex-example-2 -lpthread && ./mutex-example-2

thread 2 - start to read

thread 2 - end of reading

thread 2 - start to write

thread 2 - end of reading

thread 1 - start to read

thread 1 - end of reading

thread 1 - start to write

thread 1 - end of reading

-- global_para is 3 --

因为是串行读写，程序运行慢了很多，但结果正确了。

3 使用std::lock_guard

$ cat mutex-example-3.cpp

#include //ptrinf,perror

#include //exit

#include //pthread_xxx

#include //sleep

#include //std::mutex

int global_para = 0;

std::mutex g_mutex;

void *do_sth(void *p)

{

long i = (long)p;

const std::lock_guard<:mutex> lock(g_mutex);

printf("thread %d - start to read\n", i);

int temp = global_para;

sleep(2);

printf("thread %d - end of reading\n", i);

printf("thread %d - start to write\n", i);

sleep(2);

global_para = temp + (int)i;

printf("thread %d - end of reading\n", i);

return NULL;

}

int main()

{

pthread_t t1, t2;

pthread_create(&t1, 0, do_sth, (void *)1);

pthread_create(&t2, 0, do_sth, (void *)2);

pthread_join(t1, NULL);

pthread_join(t2, NULL);

printf("-- global_para is %d --\n", global_para);

return 0;

}

$ g++ mutex-example-3.cpp -o mutex-example-3 -lpthread && ./mutex-example-3

thread 2 - start to read

thread 2 - end of reading

thread 2 - start to write

thread 2 - end of reading

thread 1 - start to read

thread 1 - end of reading

thread 1 - start to write

thread 1 - end of reading

-- global_para is 3 --

参考