pthread_cond_wait

第一：
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>

int count ;

pthread_mutex_t   lock;

pthread_cond_t    cond;

void *thread1_handle(void *arg)
{
pthread_mutex_lock(&lock);
//count--;
while(count <=  0)
  pthread_cond_wait(&cond,&lock);
printf("in 1st the count value is :%d\n",count);
printf("%s\n",arg);
pthread_mutex_unlock(&lock);
//pthread_detach(pthread_self());
pthread_exit((void *)1);
}

void *thread2_handle(void *arg)
{
pthread_mutex_lock(&lock);
count += 2;
printf("in 2nd the count value is :%d\n",count);
printf("%s\n",arg);
pthread_cond_signal(&cond);
pthread_mutex_unlock(&lock);
pthread_exit((void *)2);
}

int main(int argc,char **argv)
{

 pthread_t   tid1,tid2;
 int         retval;
 char        buffer1[]=" 1st  thread";
 char        buffer2[]="2nd   thread";
 void        *p1,*p2;

 pthread_mutex_init(&lock,NULL);

 pthread_cond_init(&cond,NULL);
 retval = pthread_create(&tid1,NULL,(void *)thread1_handle,buffer1);
 if(retval != 0)
{
printf("pthread_create  error:%s\n",strerror(errno));
exit(errno);
}

 retval = pthread_create(&tid2,NULL,(void *)thread2_handle,buffer2);
 if(retval != 0)
{
printf("pthread_create  error:%s\n",strerror(errno));
exit(errno);
}

retval = pthread_join(tid1,&p1);
if(retval != 0)
{
printf("pthread join  error: %s",strerror(errno));
_exit(errno);
}
printf("pthread 1st  exit code:%d\n",(int)p1);

retval = pthread_join(tid2,&p2);
if(retval != 0)
{
printf("pthread join error:%s\n",strerror(errno));
exit(errno);
}
printf("pthread  2nd exit code :%d\n",(int)p2);

exit(0);
}

in 2nd the count value is :2
2nd   thread
in 1st the count value is :2
 1st  thread
pthread 1st  exit code:1
pthread  2nd exit code :2

第二：
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>

int count ;

pthread_mutex_t   lock;

pthread_cond_t    cond;

void *thread1_handle(void *arg)
{
pthread_mutex_lock(&lock);
//count--;
while(count <=  0)
  pthread_cond_wait(&cond,&lock);
printf("in 1st the count value is :%d\n",count);
printf("%s\n",arg);
pthread_mutex_unlock(&lock);
pthread_exit((void *)1);
pthread_detach(pthread_self());
}

void *thread2_handle(void *arg)
{
pthread_mutex_lock(&lock);
count += 2;
printf("in 2nd the count value is :%d\n",count);
printf("%s\n",arg);
pthread_cond_signal(&cond);
pthread_mutex_unlock(&lock);
pthread_exit((void *)2);
}

int main(int argc,char **argv)
{

 pthread_t   tid1,tid2;
 int         retval;
 char        buffer1[]=" 1st  thread";
 char        buffer2[]="2nd   thread";
 void        *p1,*p2;

 pthread_mutex_init(&lock,NULL);

 pthread_cond_init(&cond,NULL);
 retval = pthread_create(&tid1,NULL,(void *)thread1_handle,buffer1);
 if(retval != 0)
{
printf("pthread_create  error:%s\n",strerror(errno));
exit(errno);
}

 retval = pthread_create(&tid2,NULL,(void *)thread2_handle,buffer2);
 if(retval != 0)
{
printf("pthread_create  error:%s\n",strerror(errno));
exit(errno);
}

retval = pthread_join(tid1,&p1);
if(retval != 0)
{
printf("pthread join  error: %s",strerror(errno));
_exit(errno);//不fflush
}
printf("pthread 1st  exit code:%d\n",(int)p1);

retval = pthread_join(tid2,&p2);
if(retval != 0)
{
printf("pthread join error:%s\n",strerror(errno));
exit(errno);
}
printf("pthread  2nd exit code :%d\n",(int)p2);

exit(0);
}

结果：
in 2nd the count value is :2
2nd   thread
in 1st the count value is :2
1st  thread
1st   thread  detached
pthread 1st  exit code:1
pthread  2nd exit code :2

detach过后还没有报错，恩，有点怪

第三：

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>

int count ;

pthread_mutex_t   lock;

pthread_cond_t    cond;

void *thread1_handle(void *arg)
{
pthread_mutex_lock(&lock);
count--;
while(count <=  0)
  pthread_cond_wait(&cond,&lock);
printf("in 1st the count value is :%d\n",count);
printf("%s\n",arg);
pthread_mutex_unlock(&lock);
pthread_exit((void *)1);
pthread_detach(pthread_self());
}

void *thread2_handle(void *arg)
{
pthread_mutex_lock(&lock);
count += 2;
printf("in 2nd the count value is :%d\n",count);
printf("%s\n",arg);
pthread_cond_signal(&cond);
pthread_mutex_unlock(&lock);
pthread_exit((void *)2);
}

int main(int argc,char **argv)
{

 pthread_t   tid1,tid2;
 int         retval;
 char        buffer1[]=" 1st  thread";
 char        buffer2[]="2nd   thread";
 void        *p1,*p2;

 pthread_mutex_init(&lock,NULL);

 pthread_cond_init(&cond,NULL);
 retval = pthread_create(&tid1,NULL,(void *)thread1_handle,buffer1);
 if(retval != 0)
{
printf("pthread_create  error:%s\n",strerror(errno));
exit(errno);
}

 retval = pthread_create(&tid2,NULL,(void *)thread2_handle,buffer2);
 if(retval != 0)
{
printf("pthread_create  error:%s\n",strerror(errno));
exit(errno);
}

retval = pthread_join(tid1,&p1);
if(retval != 0)
{
printf("pthread join  error: %s",strerror(errno));
exit(errno);
}
printf("pthread 1st  exit code:%d\n",(int)p1);

retval = pthread_join(tid2,&p2);
if(retval != 0)
{
printf("pthread join error:%s\n",strerror(errno));
exit(errno);
}
printf("pthread  2nd exit code :%d\n",(int)p2);

exit(0);
}

结果：
in 2nd the count value is :1
2nd   thread
in 1st the count value is :1
1st  thread
1st   thread  detached
pthread 1st  exit code:1
pthread  2nd exit code :2
本来想法是：2，1  看来没有机制来控制，竞争关系，只是1st先create造成了他先执行

第四：
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>
#include <string.h>

int count ;

pthread_mutex_t   lock;

pthread_cond_t    cond;

void *thread1_handle(void *arg)
{
pthread_mutex_lock(&lock);
count--;
while(count <=  0)
  pthread_cond_wait(&cond,&lock);
printf("in 1st the count value is :%d\n",count);
printf("%s\n",arg);
pthread_mutex_unlock(&lock);
if(pthread_detach(pthread_self()) == 0)
   printf("1st   thread  detached\n");
pthread_exit((void *)1);
}

void *thread2_handle(void *arg)
{
pthread_mutex_lock(&lock);
count += 2;
printf("in 2nd the count value is :%d\n",count);
printf("%s\n",arg);
pthread_cond_signal(&cond);
pthread_mutex_unlock(&lock);
pthread_exit((void *)2);
}

int main(int argc,char **argv)
{

 pthread_t   tid1,tid2;
 int         retval;
 char        buffer1[]="1st  thread";
 char        buffer2[]="2nd   thread";
 void        *p1,*p2;

 pthread_mutex_init(&lock,NULL);

 pthread_cond_init(&cond,NULL);
 retval = pthread_create(&tid2,NULL,(void *)thread2_handle,buffer2);
 if(retval != 0)
{
printf("pthread_create  error:%s\n",strerror(errno));
exit(errno);
}

 retval = pthread_create(&tid1,NULL,(void *)thread1_handle,buffer1);
 if(retval != 0)
{
printf("pthread_create  error:%s\n",strerror(errno));
exit(errno);
}

retval = pthread_join(tid1,&p1);
if(retval != 0)
{
printf("pthread join  error: %s",strerror(errno));
exit(errno);
}
printf("pthread 1st  exit code:%d\n",(int)p1);

retval = pthread_join(tid2,&p2);
if(retval != 0)
{
printf("pthread join error:%s\n",strerror(errno));
exit(errno);
}
printf("pthread  2nd exit code :%d\n",(int)p2);

exit(0);
}

结果：
in 2nd the count value is :2
2nd   thread
in 1st the count value is :1
1st  thread
1st   thread  detached
pthread 1st  exit code:1
pthread  2nd exit code :2
果然是这种竞争造成的后果；
可以
while()
  pthread_cond_wait()
count--;
值得注意，线程是公平执行的，当然还得看具体的调度机制