Multithreaded Programming Guide

Set the Mutex Type Attribute

pthread_mutexattr_settype(3THR)

#include <pthread.h>

int pthread_mutexattr_settype(pthread_mutexattr_t  *attr , int type);

pthread_mutexattr_settype(3THR) sets the mutex type attribute. The default value of the type attribute is PTHREAD_MUTEX_DEFAULT.

The type argument specifies the type of mutex. 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 will 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 will return with an error. A thread attempting to unlock a mutex which another thread has locked will return with an error. A thread attempting to unlock an unlocked mutex will return with an error.


PTHREAD_MUTEX_RECURSIVE

A thread attempting to relock this mutex without first unlocking it will 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 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 will return with an error. A thread attempting to unlock an unlocked mutex will 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 is allowed to map this mutex to one of the other mutex types. (For Solaris threads, PTHREAD_PROCESS_DEFAULT is mapped to PTHREAD_PROCESS_NORMAL.)

Return Values

If successful, the pthread_mutexattr_settype function returns zero. Otherwise, an error number is returned to indicate the error.


EINVAL

The value type is invalid.


EINVAL

The value specified by attr is invalid.