c - posix 互斥锁没有按预期工作

Question

我有一个问题。

我初始化了一个静态互斥锁，并试图在我的所有函数中锁定它。 我不小心忘记在其中一个函数中解锁它，但是当我调用另一个也试图获取互斥锁的函数时，似乎没有发生死锁。

有人可以解释一下为什么不会发生死锁吗？

解释我的问题场景的代码:

 pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

 void main(void)
 {
   func1();  // Mutex acquired initially but not released at end
   func2();  // This function acquires mutex even though mutex was not released by func1();

 }


 void func1(void)
 {
   pthread_mutex_lock(&mutex);

   printf("I am in func1\n");

   //MUTEX NOT UNLOCKED
 }

 void func2(void)
 {
   pthread_mutex_lock(&mutex);

   printf("I am in func2\n");

   //MUTEX AGAIN NOT UNLOCKED
 }

谁能解释一下为什么 func2() 中没有发生死锁，因为 func1() 中没有释放互斥量？

Answer 1

根据规范，PTHREAD_MUTEX_INITIALIZER 相当于一个默认的互斥体:

In cases where default mutex attributes are appropriate, the macro PTHREAD_MUTEX_INITIALIZER can be used to initialise mutexes that are statically allocated. The effect is equivalent to dynamic initialisation by a call to pthread_mutex_init() with parameter attr specified as NULL, except that no error checks are performed.

对于默认的互斥量，试图锁定已被调用线程锁定的互斥量会导致未定义的行为:

If the mutex type is PTHREAD_MUTEX_DEFAULT, attempting to recursively lock the mutex results in undefined behaviour.