Manual Pages  — PTHREAD_MUTEXATTR

The pthread_mutexattr_setpshared() function sets the process-shared attribute of attr to the value specified in pshared. The argument pshared may have one of the following values:

PTHREAD_PROCESS_PRIVATE
	The mutex may only be used by threads in the same process as the one that created the object.
PTHREAD_PROCESS_SHARED	The mutex may be used by threads in processes other than the one that created the object, assuming other processes share access to the memory where the mutex was allocated.

See libthr(3) for details of the implementation of the shared mutexes, and their limitations.

The pthread_mutexattr_setrobust() function specifies robustness attribute of the mutex. Possible values for the robust argument are

PTHREAD_MUTEX_STALLED
	No special actions are taken if the thread owning the mutex is terminated without unlocking the mutex lock. This can lead to deadlocks if no other thread can unlock the mutex. This is the default value.
PTHREAD_MUTEX_ROBUST	If the process containing the owning thread of a robust mutex, or owning thread, terminates while holding the mutex lock, the next thread that acquires the mutex is notified about the termination by the return value EOWNERDEAD from the locking function. Then, either pthread_mutex_consistent(3) can be used to repair the mutex lock state, or pthread_mutex_unlock(3) can unlock the mutex lock but also put it an unusable state, where all further attempts to acquire it result in the ENOTRECOVERABLE error.

The pthread_mutexattr_settype() function sets the type of the mutex. The type affects the behavior of calls which lock and unlock the mutex. The possible values for the type argument are

PTHREAD_MUTEX_NORMAL	Both recursive locking, and unlocking when the lock is not owned by the current thread, cause an error to be returned from the corresponding functions. This matches PTHREAD_MUTEX_ERRORCHECK but somewhat contradicts the behavior mandated by POSIX.
PTHREAD_MUTEX_ERRORCHECK
	Both recursive locking, and unlocking when the lock is not owned by the current thread, cause an error returned from the corresponding functions.
PTHREAD_MUTEX_RECURSIVE	Recursive locking is allowed. Attempt to unlock when current thread is not an owner of the lock causes an error to be returned.
PTHREAD_MUTEX_DEFAULT	The FreeBSD implementation maps this type to PTHREAD_MUTEX_ERRORCHECK type.

The pthread_mutexattr_get*() functions copy the value of the attribute that corresponds to each function name to the location pointed to by the second function parameter.