导致僵局的地方？

Question

我打算让两个线程等待来自第三个线程的信号。

这两个线程完成相同的工作，但其中只有一个线程同时获取信号。一旦满足某个条件（捕捉到的信号的数量），它们自行终止。

然后最后主线程取消第三个线程。

我有死锁，但无法弄清楚问题出在哪里。

#include <pthread.h> 
#include <stdio.h> 

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; 
pthread_cond_t cond = PTHREAD_COND_INITIALIZER; 

int n = 0; 
int count = 0; 

void* func1(void *ptr) 
{ 
    while(1) 
    { 
     pthread_mutex_lock(&mutex); 

     // wait for func3 to signal 
     pthread_cond_wait(&cond, &mutex); 
     count++; 

     if(count > 10) 
     { 
      printf("number %d terminate func1\n", n); 
      return (NULL); 
     } 
     else 
     { 
      printf("func1 got number:%d\n", n); 
     } 
     pthread_mutex_unlock(&mutex); 
    } 
} 

void* func2(void *ptr) 
{ 
    while(1) 
    { 
     pthread_mutex_lock(&mutex); 

     // wait for func3 to signal 
     pthread_cond_wait(&cond, &mutex); 
     count++; 

     if(count > 10) 
     { 
      printf("number %d terminate func2\n", n); 
      return (NULL); 
     } 
     else 
     { 
      printf("func2 got number:%d\n", n); 
     } 
     pthread_mutex_unlock(&mutex); 
    } 
}  

void* func3(void *ptr) 
{ 
    while(1) 
    { 
     pthread_mutex_lock(&mutex); 
     n++; 
     pthread_cond_signal(&cond); 
     pthread_mutex_unlock(&mutex); 
    } 
} 


int main(int argc, char *argv[]) 
{ 
    pthread_t t1, t2, t3; 

    pthread_create(&t1, NULL, func1, NULL); 
    pthread_create(&t2, NULL, func2, NULL); 
    pthread_create(&t3, NULL, func3, NULL); 

    pthread_join(t1, NULL); 
    pthread_join(t2, NULL); 

    pthread_cancel(t3); 

    return 0; 
} 

Answer 1

你不是解锁互斥时func1或func2退出。

Answer 2

我认为问题是（如pst points out）return (NULL);在您的func1和func2函数中;因为pthread_cond_wait(3posix)返回时，互斥锁，当他们退出，互斥留锁定：

These functions atomically release mutex and cause the 
    calling thread to block on the condition variable cond; 
    ... 
    Upon successful return, the mutex shall have been locked and 
    shall be owned by the calling thread. 

尝试return (NULL);之前解锁你的互斥量。