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


#define THREAD_MAX 4


pthread_mutex_t mutex;
pthread_t thread[THREAD_MAX];


static int tries;
static int started;


void print_it(int *arg)
{
pthread_t tid;
tid = pthread_self();
printf("Thread %lx was canceled on its %d try.\n",tid,*arg);
}


void *Search_Num(int arg)
{
pthread_t tid;
int num;
int k=0,h=0,j;
int ntries;
tid = pthread_self();

/*while(pthread_mutex_trylock(&mutex) == EBUSY)
{
printf("**************busy****************\n");
pthread_testcancel();
}*/
srand(arg);
num = rand()&0xFFFFFF;
//pthread_mutex_unlock(&mutex);

printf("thread num %lx\n",tid);

ntries = 0;
pthread_setcancelstate(PTHREAD_CANCEL_ENABLE,NULL);
pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED,NULL);

pthread_cleanup_push((void *)print_it,(void *)&ntries);

while(1)
{
num = (num+1)&0xffffff;
ntries++;

if(arg == num)
{
//只允许一个线程操作此处
while(pthread_mutex_trylock(&mutex) == EBUSY) { 
//一个线程操作后其余线程进入次循环挂起，等待pthread_cancel函数发送cancel信号终止线程
k++;
if(k == 10000)
{
printf("----------2busy2-----------\n");
}

pthread_testcancel();
}
tries = ntries;
//pthread_mutex_unlock(&mutex);  //如果加上这句话，将会有好几个线程找到主函数中设定的值pid
printf("Thread %lx found the number!\n",tid);

for(j = 0;j<THREAD_MAX;j++)
{
if(thread[j]!=tid)
{
pthread_cancel(thread[j]);
}
}

break;
}
if(ntries0 == 0)
{
h++;
/*线程阻塞，其他线程争夺资源，或者是等待pthread_cancel函数发送cancel信号终止线程*/
pthread_testcancel();
/*这是为了弄明白pthread_testcancel函数的作用而设置的代码段*/
if(h == 10000)
{
h = 0;
printf("----------thread num %lx-------------\n",tid);
}
}
}
pthread_cleanup_pop(0);
return (void *)0;
}


int main()
{
int i,pid;

pid = getpid(); //设置要查找的数

pthread_mutex_init(&mutex,NULL);
printf("Search the num of %d\n",pid);
for(started = 0; started < THREAD_MAX; started++)
{
pthread_create(&thread[started],NULL,(void *)Search_Num,(void *)pid);
}

for(i = 0; i < THREAD_MAX; i++)
{
printf("-----------i = %d--------------\n",i);
pthread_join(thread[i],NULL);
}
printf("It took %d tries ot find the number!\n",tries);
return 0;
}

Search the num of 6531
-----------i = 0--------------
thread num b6fbcb70
thread num b67bbb70
thread num b5fbab70
thread num b77bdb70
----------thread num b67bbb70-------------
Thread b67bbb70 found the number!
----------thread num b6fbcb70-------------
----------thread num b77bdb70-------------
----------2busy2-----------
----------thread num b5fbab70-------------
----------2busy2-----------
Thread b5fbab70 was canceled on its 1174527 try.
Thread b77bdb70 was canceled on its 1023100 try.
-----------i = 1--------------
Thread b6fbcb70 was canceled on its 1174527 try.
-----------i = 2--------------
-----------i = 3--------------
It took 1174527 tries ot find the number!