VMS Help DCE_THREADS, Application Routines, pthread_mutex_lock  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  NAME

      pthread_mutex_lock - Locks an unlocked mutex

  SYNOPSIS

      #include <pthread.h>

      int pthread_mutex_lock( pthread_mutex_t *mutex );

  PARAMETERS

      mutex                Mutex that is locked.

  DESCRIPTION

  The pthread_mutex_lock() routine locks a mutex. If the mutex is locked
  when a thread calls this routine, the thread waits for the mutex to
  become available.

  The thread that has locked a mutex becomes its current owner and remains
  the owner until the same thread has unlocked it. This routine returns
  with the mutex in the locked state and with the current thread as the
  mutex's current owner.

  If you specified a fast mutex in a call to
  pthread_mutexattr_setkind_np(), a deadlock can result if the current
  owner of a mutex calls this routine in an attempt to lock the mutex a
  second time. If you specified a recursive mutex in a call to
  pthread_mutexattr_setkind_np(), the current owner of a mutex can relock
  the same mutex without blocking.  If you specify a nonrecursive mutex in
  a call to pthread_mutexattr_setkind_np(), an error is returned and the
  thread does not block if the current owner of a mutex calls this routine
  in an attempt to lock the mutex a second time.

  The preemption of a lower-priority thread that locks a mutex possibly
  results in the indefinite blocking of higher-priority threads waiting
  for the same mutex. The execution of the waiting higher-priority threads
  is blocked for as long as there is a sufficient number of runable
  threads of any priority between the lower-priority and higher-priority
  values. Priority inversion occurs when any resource is shared between
  threads with different priorities.

  RETURN VALUES

  If the function fails, errno may be set to one of the following values:

    Return   Error       Description
    _____________________________________________________________
     0                   Successful completion.

    -1      [EINVAL]     The value specified by mutex is invalid.

    -1      [EDEADLK]    A deadlock condition is detected.

  RELATED INFORMATION

      FUNCTIONS:  pthread_mutexattr_setkind_np
                  pthread_mutex_destroy
                  pthread_mutex_init
                  pthread_mutex_trylock
                  pthread_mutex_unlock