Linux下进程同步问题小例

以下代码利用mmap给内存文件分配空间，利用fork产生父子进程，通过semaphore中的信号量进行同步和死锁操作。完成了父子进程的同步运行。

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <semaphore.h>
#include <sys/mman.h>
int* count = 0;
sem_t *mutex1 = NULL;
sem_t *mutex2 = NULL;
int finish = 0;
int main()
{
    mutex1 = (sem_t*)mmap(NULL, sizeof(sem_t), PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
    mutex2 = (sem_t*)mmap(NULL, sizeof(sem_t), PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
    count = (int*)mmap(NULL,sizeof(int), PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1,0);
    sem_init(mutex1, 1, 1);
    sem_init(mutex2, 1, 0);
    *count = 0;
    if(fork()==0)
    {
        while(1)
        {
            printf("child continue!n");
            sem_wait(mutex1);
            *count += 2;
            printf("child:%dn",*count);
            finish++;
            sem_post(mutex2);
            if(finish == 10)
                break;
        }
        printf("child Finish!n");
        exit(0);
    }

    while(1)
    {
        printf("father continue!n");
        sem_wait(mutex2);
        *count -= 1;
        printf("father:%dn",*count);
        finish++;
        sem_post(mutex1);
        if(finish == 10)
            break;
    }
    sem_destroy(mutex1);
    sem_destroy(mutex2);
    munmap(mutex1, sizeof(sem_t));
    munmap(mutex2, sizeof(sem_t));
    munmap(count, sizeof(int));
    printf("Finished All!n");
    return 0;
}

在linux下进行编译

[root@localhost myfile]# gcc testsem.c  -o testsem -lpthread

运行结果：

[root@localhost myfile]# ./testsem 
father continue!
child continue!
child:2
child continue!
father:1
father continue!
child:3
child continue!
father:2
father continue!
child:4
child continue!
father:3
father continue!
child:5
child continue!
father:4
father continue!
child:6
child continue!
father:5
father continue!
child:7
child continue!
father:6
father continue!
child:8
child continue!
father:7
father continue!
child:9
child continue!
father:8
father continue!
child:10
child continue!
father:9
father continue!
child:11
child Finish!
father:10
Finished All!

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