pthread_mutex_init(3T)                               pthread_mutex_init(3T)
                               Pthread Library

 NAME
      pthread_mutex_init(), pthread_mutex_destroy() - initialize or destroy
      a mutex.

 SYNOPSIS
      #include <pthread.h>

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

      pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

      int pthread_mutex_destroy(
         pthread_mutex_t *mutex
      );

 PARAMETERS
           mutex     Pointer to the mutex to be initialized or destroyed.

           attr      Pointer to the attributes object that defines the
                     characteristics of the mutex to be initialized. If the
                     pointer is NULL, default attributes are used.

 DESCRIPTION
      The pthread_mutex_init() function initializes the mutex referenced by
      mutex with the attributes attr.  If the parameter attr is NULL, the
      default mutex attributes are used.  Refer to
      pthread_mutexattr_init(3T) for a list of default mutex attributes.
      After successful initialization, the mutex is initialized, unlocked,
      and ready to be used in mutex operations.  A mutex should be
      initialized only once or the resulting behavior is undefined.  The
      pthread_once() function provides a way to ensure that a mutex is
      initialized only once.

      The macro PTHREAD_MUTEX_INITIALIZER can be used to initialize mutexes
      that are statically allocated.  These mutexes will be initialized with
      default attributes.  The pthread_mutex_init() function does not need
      to be called for statically initialized mutexes.

      If the process-shared attribute in the mutex attributes object
      referenced by attr is defined as PTHREAD_PROCESS_SHARED, the mutex
      must be allocated such that the processes sharing the mutex have
      access to it. This may be done through the memory-mapping functions
      (see mmap(2)) or the shared memory functions (see shmget(2)).

      The pthread_mutex_destroy() function destroys the mutex referenced by
      mutex.  This function may set mutex to an invalid value.  The
      destroyed mutex can be reinitialized using the function
      pthread_mutex_init().  If the mutex is used after destruction in any

 Hewlett-Packard Company            - 1 -  HP-UX Release 11.00: October 1997

 pthread_mutex_init(3T)                               pthread_mutex_init(3T)
                               Pthread Library

      mutex call, the resulting behavior is undefined.

      A mutex should be destroyed only when it is unlocked.  Destroying a
      mutex that is currently being used results in undefined behavior.

 RETURN VALUE
      Upon successful completion, pthread_mutex_init() and
      pthread_mutex_destroy() return zero. Otherwise, an error number is
      returned to indicate the error (the errno variable is not set).

 ERRORS
      If any of the following occur, the pthread_mutex_init() function
      returns the corresponding error number:

           [EAGAIN]       The necessary resources (other than memory) to
                          initialize mutex were not available.

           [ENOMEM]       There is insufficient memory available in which to
                          initialize mutex.

           [EPERM]        The caller does not have the necessary permission
                          to perform the mutex initialization.

      For each of the following conditions, if the condition is detected,
      the pthread_mutex_init() function returns the corresponding error
      number:

           [EINVAL]       The value specified by mutex or attr is invalid.

           [EBUSY]        mutex is an already initialized mutex.

           [EFAULT]       mutex parameter points to an illegal address.

      For each of the following conditions, if the condition is detected,
      the pthread_mutex_destroy() function returns the corresponding error
      number:

           [EINVAL]       mutex is not a valid mutex.

           [EBUSY]        mutex is currently locked or in use by another
                          thread.

 WARNINGS
      The space for the mutex must be allocated before calling
      pthread_mutex_init().  Undefined behavior will result if the process-
      shared attribute of attr is PTHREAD_PROCESS_SHARED and the space
      allocated for the mutex is not accessible to cooperating threads.

 AUTHOR
      pthread_mutex_init() and pthread_mutex_destroy() were derived from the
      IEEE POSIX P1003.1c standard.

 Hewlett-Packard Company            - 2 -  HP-UX Release 11.00: October 1997

 pthread_mutex_init(3T)                               pthread_mutex_init(3T)
                               Pthread Library

 SEE ALSO
      pthread_mutex_lock(3T), pthread_mutex_unlock(3T),
      pthread_mutex_trylock(3T).

 STANDARDS CONFORMANCE
      pthread_mutex_init(): POSIX 1003.1c.
      pthread_mutex_destroy(): POSIX 1003.1c.