【PTHREAD】线程互斥与同步之自旋锁

1 自旋锁类型

typedef volatile int pthread_spinlock_t;
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2 初始化与销毁自旋锁

int pthread_spin_init(pthread_spinlock_t *lock, int pshared);
int pthread_spin_destroy(pthread_spinlock_t *lock);
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• PTHREAD_PROCESS_PRIVATE
• PTHREAD_PROCESS_SHARED

3 自旋锁的加锁解锁

int pthread_spin_lock(pthread_spinlock_t *lock);
int pthread_spin_trylock(pthread_spinlock_t *lock);
int pthread_spin_unlock(pthread_spinlock_t *lock);
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4 案例：自旋锁的使用

• 源码

  #include 
  #include 
  #include 
  #include 
  #include 
  
  pthread_spinlock_t spinlock;
  
  void *start_routine_01(void *ptr)
  {
      printf("子线程(%lu)开始运行...\n", pthread_self());
      for (size_t i = 0; i < 3; i++)
      {
          pthread_spin_lock(&spinlock);
          printf("子线程(%lu)进入自旋锁\n", pthread_self());
          sleep(1);
          printf("子线程(%lu)离开自旋锁\n", pthread_self());
          pthread_spin_unlock(&spinlock);
      }
      return (void*)"9999";
  }
  
  void *start_routine_02(void *ptr)
  {
      printf("子线程(%lu)开始运行...\n", pthread_self());
      for (size_t i = 0; i < 3; i++)
      {
          pthread_spin_lock(&spinlock);
          printf("子线程(%lu)进入自旋锁\n", pthread_self());
          sleep(1);
          printf("子线程(%lu)离开自旋锁\n", pthread_self());
          pthread_spin_unlock(&spinlock);
      }
      return (void*)"9999";
  }
  
  int main(int argc, char const *argv[])
  {
      printf("主线程(%lu)开始运行...\n", pthread_self());
  
      pthread_spin_init(&spinlock, PTHREAD_PROCESS_PRIVATE);
      
      pthread_t thread_id_01;
      pthread_create(&thread_id_01, NULL, start_routine_01, NULL);
  
      pthread_t thread_id_02;
      pthread_create(&thread_id_02, NULL, start_routine_02, NULL);
  
      pthread_join(thread_id_01, NULL);
      pthread_join(thread_id_02, NULL);
  
      pthread_spin_destroy(&spinlock);
      printf("主线程(%lu)即将退出...\n", pthread_self());
      exit(EXIT_SUCCESS);
  }
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• 输出

  主线程(139684168165184)开始运行…
  子线程(139684168161024)开始运行…
  子线程(139684168161024)进入自旋锁
  子线程(139684159768320)开始运行…
  子线程(139684168161024)离开自旋锁
  子线程(139684168161024)进入自旋锁
  子线程(139684168161024)离开自旋锁
  子线程(139684168161024)进入自旋锁
  子线程(139684168161024)离开自旋锁
  子线程(139684159768320)进入自旋锁
  子线程(139684159768320)离开自旋锁
  子线程(139684159768320)进入自旋锁
  子线程(139684159768320)离开自旋锁
  子线程(139684159768320)进入自旋锁
  子线程(139684159768320)离开自旋锁
  主线程(139684168165184)即将退出…