NAME

pthread_mutex_init − Initializes a mutex. 

LIBRARY

DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS

#include <pthread.h>

int   pthread_mutex_init(
                      pthread_mutex_t   ∗mutex,
                      const pthread_mutexattr_t ∗attr);

STANDARDS

Interfaces documented on this reference page conform to industry standards as follows:

IEEE Std 1003.1c-1995, POSIX System Application Program Interface

PARAMETERS

mutexMutex to be initialized. 

attrMutex attributes object that defines the characteristics of the mutex to be initialized. 

DESCRIPTION

This routine initializes a mutex with the attributes specified by the mutex attributes object specified in the attr argument.  A mutex is a synchronization object that allows multiple threads to serialize their access to shared data. 
 

The mutex is initialized and set to the unlocked state.  If attr is set to NULL, the default mutex attributes are used.  The pthread_mutexattr_settype(3) routine can be used to specify the type of mutex that is created (normal, recursive, or errorcheck). 

Use the PTHREAD_MUTEX_INITIALIZER macro to statically initialize a mutex without calling this routine.  Statically initialized mutexes need not be destroyed using pthread_mutex_destroy(3).  Use this macro as follows:

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER

Only normal mutexes can be statically initialized. 

A mutex is a resource of the process, not part of any particular thread.  A mutex is neither destroyed nor unlocked automatically when any thread exits.  If a mutex is allocated on a stack, static initializers cannot be used on the mutex. 

RETURN VALUES

If an error condition occurs, this routine returns an integer value indicating the type of error, the mutex is not initialized, and the contents of mutex are undefined.  Possible return values are as follows:

0Successful completion. 

[EAGAIN]The system lacks the necessary resources to initialize the mutex. 

[EBUSY]The implementation has detected an attempt to reinitialize the mutex (a previously initialized, but not yet destroyed mutex). 

[EINVAL]The value specified by mutex is not a valid mutex. 

[ENOMEM]Insufficient memory exists to initialize the mutex. 

[EPERM]The caller does not have privileges to perform the operation. 

ERRORS

None

RELATED INFORMATION

Functions: pthread_mutexattr_init(3), pthread_mutexattr_gettype(3), pthread_mutexattr_settype(3), pthread_mutex_lock(3), pthread_mutex_trylock(3), pthread_mutex_unlock(3)

Manuals: Guide to DECthreads and Programmer’s Guide