Setting the Mutex Type Attribute

pthread_mutexattr_settype(3C) sets the mutex type attribute.

pthread_mutexattr_settype Syntax

#include <pthread.h>

int pthread_mutexattr_settype(pthread_mutexattr_t  *attr , int type);

The default value of the type attribute is PTHREAD_MUTEX_DEFAULT.

The type argument specifies the type of mutex. The following list describes the valid mutex types:

PTHREAD_MUTEX_NORMAL

Description:

This type of mutex does not detect deadlock. A thread attempting to relock this mutex without first unlocking the mutex deadlocks. 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

Description:

This type of mutex provides error checking. A thread attempting to relock this mutex without first unlocking the mutex returns an error. A thread attempting to unlock a mutex that another thread has locked returns an error. A thread attempting to unlock an unlocked mutex returns an error.

PTHREAD_MUTEX_RECURSIVE

Description:

A thread attempting to relock this mutex without first unlocking the mutex succeeds in locking the mutex. The relocking deadlock that 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 that another thread has locked returns an error. A thread attempting to unlock an unlocked mutex returns an error.

PTHREAD_MUTEX_DEFAULT

Description:

An implementation is allowed to map this attribute to one of the other mutex types. The Solaris implementation maps this attribute to PTHREAD_PROCESS_NORMAL.

pthread_mutexattr_settype Return Values

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

EINVAL

Description:

The value type or attr is invalid.