c - 什么是默认互斥锁属性？

Question

来自手册页:

The pthread_mutex_init() function shall initialize the mutex referenced by mutex with attributes specified by attr.
If attr is NULL, the default mutex attributes are used; the effect shall be the same as passing the address of a default mutex attributes object. Upon successful initialization, the state of the mutex becomes initialized and unlocked.

默认的互斥量属性是什么？
此代码设置了什么:pthread_mutex_t mutexLock = PTHREAD_MUTEX_INITIALIZER;?

Answer 1

您必须仔细研究 POSIX 规范才能获得互斥属性的默认值:

• pthread_mutexattr_settype()

  PTHREAD_MUTEX_DEFAULT

  Attempting to recursively lock a mutex of this type results in undefined behaviour. Attempting to unlock a mutex of this type which was not locked by the calling thread results in undefined behaviour. Attempting to unlock a mutex of this type which is not locked results in undefined behaviour. An implementation is allowed to map this mutex to one of the other mutex types.

  请注意，这可能与其他互斥锁类型不同，但它可以映射到 PTHREAD_MUTEX_NORMAL 或 PTHREAD_MUTEX_ERRORCHECK。

• pthread_mutexattr_setpshared()

  The default value of the attribute is PTHREAD_PROCESS_PRIVATE.

对于其他属性，规范似乎没有明确说明。这些属性是:

• 优先级上限属性 ( pthread_mutexattr_getprioceiling() )
• 优先继承的协议(protocol)属性(pthread_mutexattr_getprotocol())