PTHREAD_MUTEXATTR_GETTYPE(PPOSIX Programmer's ManuPTHREAD_MUTEXATTR_GETTYPE(P) NAME pthread_mutexattr_gettype, pthread_mutexattr_settype - get and set the mutex type attribute SYNOPSIS #include int pthread_mutexattr_gettype(const pthread_mutexattr_t *restrict attr, int *restrict type); int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type); DESCRIPTION The pthread_mutexattr_gettype() and pthread_mutexattr_settype() func- tions, respectively, shall get and set the mutex type attribute. This attribute is set in the type parameter to these functions. The default value of the type attribute is PTHREAD_MUTEX_DEFAULT. The type of mutex is contained in the type attribute of the mutex attributes. Valid mutex types include: PTHREAD_MUTEX_NORMAL This type of mutex does not detect deadlock. A thread attempting to relock this mutex without first unlocking it shall deadlock. Attempting to unlock a mutex locked by a different thread results in undefined behavior. Attempting to unlock an unlocked mutex results in undefined behavior. PTHREAD_MUTEX_ERRORCHECK This type of mutex provides error checking. A thread attempting to relock this mutex without first unlocking it shall return with an error. A thread attempting to unlock a mutex which another thread has locked shall return with an error. A thread attempting to unlock an unlocked mutex shall return with an error. PTHREAD_MUTEX_RECURSIVE A thread attempting to relock this mutex without first unlocking it shall succeed in locking the mutex. The relocking deadlock which can occur with mutexes of type PTHREAD_MUTEX_NORMAL cannot occur with this type of mutex. Multiple locks of this mutex shall require the same number of unlocks to release the mutex before another thread can acquire the mutex. A thread attempting to unlock a mutex which another thread has locked shall return with an error. A thread attempting to unlock an unlocked mutex shall return with an error. PTHREAD_MUTEX_DEFAULT Attempting to recursively lock a mutex of this type results in undefined behavior. Attempting to unlock a mutex of this type which was not locked by the calling thread results in undefined behavior. Attempting to unlock a mutex of this type which is not locked results in undefined behavior. An implementation may map this mutex to one of the other mutex types. RETURN VALUE Upon successful completion, the pthread_mutexattr_gettype() function shall return zero and store the value of the type attribute of attr into the object referenced by the type parameter. Otherwise, an error shall be returned to indicate the error. If successful, the pthread_mutexattr_settype() function shall return zero; otherwise, an error number shall be returned to indicate the error. ERRORS The pthread_mutexattr_settype() function shall fail if: EINVAL The value type is invalid. The pthread_mutexattr_gettype() and pthread_mutexattr_settype() func- tions may fail if: EINVAL The value specified by attr is invalid. These functions shall not return an error code of [EINTR]. The following sections are informative. EXAMPLES None. APPLICATION USAGE It is advised that an application should not use a PTHREAD_MUTEX_RECUR- SIVE mutex with condition variables because the implicit unlock per- formed for a pthread_cond_timedwait() or pthread_cond_wait() may not actually release the mutex (if it had been locked multiple times). If this happens, no other thread can satisfy the condition of the predi- cate. RATIONALE None. FUTURE DIRECTIONS None. SEE ALSO pthread_cond_timedwait() , the Base Definitions volume of IEEE Std 1003.1-2001, COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . IEEE/The Open Group 2003 PTHREAD_MUTEXATTR_GETTYPE(P)