Hands-On System Programming with Linux

Mutex types

A mutex can be one of four types, the default usually—but not always (it depends upon the implementation)—being the normal mutex. The type of mutex used affects the behavior of the lock and unlock. The types are: PTHREAD_MUTEX_NORMAL, PTHREAD_MUTEX_ERRORCHECK, PTHREAD_MUTEX_RECURSIVE, and PTHREAD_MUTEX_DEFAULT.

The system man page on pthread_mutex_lock(3) describes the behavior depending on the mutex type with a table; for the reader's convenience, we have reproduced the same here.

If a thread attempts to relock a mutex that it has already locked, pthread_mutex_lock(3) shall behave as described in the relock column of the following table. If a thread attempts to unlock a mutex that it has not locked or a mutex which is unlocked, ...