thread互斥测试

thread互斥测试

任务列表：编译运行附件中的代码，并说明程序的功能
一、代码编译

openeuler下直接运行：

发现没有适当的输出
发现传参函数，于是输入./wc 1.txt 2.txt,得到结果：

继续分析代码：

此代码为Linux中互斥锁的pthread_mutex_t的使用，互斥锁可以保持多个进程同步，互斥锁的使用过程中，主要有pthread_mutex_init，pthread_mutex_destory，pthread_mutex_lock，pthread_mutex_unlock这几个函数以完成锁的初始化，锁的销毁，上锁和释放锁操作。

include <stdio.h>

include <stdlib.h>

include <pthread.h>

include <ctype.h>

struct arg_set {
char *fname;
int count;
};

struct arg_set *mailbox = NULL;
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;//静态化创建锁
pthread_cond_t flag = PTHREAD_COND_INITIALIZER;

void *count_words(void *);
int main(int argc, char *argv[])
{
pthread_t t1, t2;
struct arg_set args1, args2;
int reports_in = 0;
int total_words = 0;

if ( argc != 3 ){//未输入两个文件的退出情况
	printf("usage: %s file1 file2\n", argv[0]);
	exit(1);
}

args1.fname = argv[1];
args1.count = 0;
pthread_create(&t1, NULL, count_words, (void *) &args1);

args2.fname = argv[2];
args2.count = 0;
pthread_create(&t2, NULL, count_words, (void *) &args2);

pthread_mutex_lock(&lock);
while( reports_in < 2 ){
	printf("MAIN: waiting for flag to go up\n");
	pthread_cond_wait(&flag, &lock); 
	printf("MAIN: Wow! flag was raised, I have the lock\n");
	printf("%7d: %s\n", mailbox->count, mailbox->fname);
	total_words += mailbox->count;
	if ( mailbox == &args1) 
		pthread_join(t1,NULL);
	if ( mailbox == &args2) 
		pthread_join(t2,NULL);
	mailbox = NULL;
	pthread_cond_signal(&flag);	
	reports_in++;
}
pthread_mutex_unlock(&lock);

printf("%7d: total words\n", total_words);

}
void *count_words(void *a)
{
struct arg_set *args = a;
FILE *fp;
int c, prevc = '\0';

if ( (fp = fopen(args->fname, "r")) != NULL ){
	while( ( c = getc(fp)) != EOF ){
		if ( !isalnum(c) && isalnum(prevc) )
			args->count++;
		prevc = c;
	}
	fclose(fp);
} else 
	perror(args->fname);
printf("COUNT: waiting to get lock\n");
pthread_mutex_lock(&lock);	
printf("COUNT: have lock, storing data\n");
if ( mailbox != NULL ){
	printf("COUNT: oops..mailbox not empty. wait for signal\n");
	pthread_cond_wait(&flag,&lock);
}
mailbox = args;			
printf("COUNT: raising flag\n");
pthread_cond_signal(&flag);	
printf("COUNT: unlocking box\n");
pthread_mutex_unlock(&lock);	
return NULL;

}