[英]Using Mutex Lock/Unlock and Broadcast for pthreads in C
這是我的第一篇文章,我很興奮。
我的問題是我在C中創建了一個Rock,Paper,Scissors程序,其中父進程創建了2個線程。 然后,這2個線程會隨機扔石頭,紙或剪刀,並將該值返回給父對象,並在其中對其計數並吐出3個回合的結果,然后進行最后的計數。
我的問題是我無法正確啟動線程,我在thread_function1中等待它們,但是它們僅完成了一輪,即使那樣我也沒有得到兩個線程。 如果有人可以請大家說明一下,我將不勝感激! 謝謝
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <pthread.h>
#include <sys/time.h>
#define NTHREADS 2
struct timeval tv;
void *thread_function1();
void *thread_function2();
char *guess_string(int g);
int wins[3];
int cmd_ready = 0;
int x1=0, x2=1, count=0;
int guess, object, turns, i, j, k,l, winner, cmd, go, y;
pthread_mutex_t cv_m;
pthread_mutex_t count_mutex;
pthread_cond_t cv;
int myindex;
int flag;
int throws[3];
int main(int argc, char *argv[])
{
wins[0] = 0; wins[1] = 0;
if ((argc != 2) || ((turns = atoi(argv[1])) <= 0))
{
fprintf(stderr,"Usage: %s turns\n", argv[0]);
return 0;
}
pthread_t thread_id1, thread_id2;
if (pthread_create(&thread_id1, NULL, thread_function1,&x1) != 0)
perror("pthread_create"),
exit(1);
if (pthread_create(&thread_id2, NULL, thread_function1,&x2) != 0)
perror("pthread_create"),
exit(1);
printf("Beginning %d Rounds...\nFight!\n", turns);
printf("Child 1 TID: %d\n", (unsigned int) thread_id1);
printf("Child 2 TID: %d\n", (unsigned int) thread_id2 );
for(k=0; k<turns; k++)
{
pthread_mutex_lock (&cv_m);
cmd = go;
cmd_ready = 2;
pthread_cond_broadcast(&cv);
pthread_mutex_unlock(&cv_m);
printf("------------------------\n");
printf("Round: %d\n", k+1);
printf("Child %d throws %s!\n",myindex+1, guess_string(myindex));
pthread_mutex_lock (&count_mutex);
winner = find_winner(throws[0], throws[1]);
while(count == 2){
if(winner >= 0)
{
printf("Child %d Wins!\n", winner+1);
wins[winner]++;
printf("6\n");
}else
{
printf("Game is a Tie!\n");
}
go--;
count = 0;
pthread_mutex_unlock(&count_mutex);
}
}
pthread_join(thread_id1,NULL);
pthread_join(thread_id2,NULL);
printf("------------------------\n");
printf("------------------------\n");
printf("Result:\n");
printf("Child 1: %d\n", wins[0]);
printf("Child 2: %d\n", wins[1]);
printf("Ties: %d\n", turns - (wins[0] + wins[1]));
printf("Child %d Wins!\n", (wins[0] > wins[1]) ? 1 : 2);
pthread_mutex_destroy(&cv_m);
pthread_cond_destroy(&cv);
pthread_exit(NULL);
return 0;
}
void *thread_function1(void *p)
{
struct timeval tv;
myindex = *(int *)p;
gettimeofday(&tv, NULL);
srand(tv.tv_sec + tv.tv_usec + getpid());
printf("1\n");
pthread_mutex_lock (&cv_m);
while(cmd_ready == 0)
{
printf("2\n");
pthread_cond_wait(&cv, &cv_m);
}
printf("3\n");
throws[myindex] = rand() % 3;
cmd_ready--;
printf("Ready: %d\n",cmd_ready);
pthread_mutex_unlock (&cv_m);
printf("4\n");
pthread_mutex_lock (&count_mutex);
count++;
printf("Count %d\n", count);
pthread_mutex_unlock(&count_mutex);
while(count == 2){
printf("5\n");
return NULL;
}
}
char *guess_string(int g){
switch(g){
case 0:
return "Rock";
break;
case 1:
return "Paper";
break;
case 2:
return "Scissors";
break;
}
}
int find_winner(int g1, int g2){
if(g1 == g2)
return -1;
else if ((g1 == 2) && (g2 == 0))
return 1;
else if ((g1 == 0) && (g2 == 2))
return 0;
else
return (g1 > g2) ? 0 : 1;
}
您似乎沒有使用pthread_mutex_init
或pthread_cond_init
初始化互斥量或條件。
兩個線程都在沒有保護的情況下修改了變量myindex
,用於更新此變量的第二個線程將是要報告的線程。
您還指望線程在main搶到鎖並發布廣播之前的條件下開始掛起,這可能會導致main首先到達那里而您的線程無法准備就緒的情況。
那應該是一個開始。
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