mutexinit.c

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

/*
 *  $Id: mutexinit.c,v 1.4 2002/07/01 22:33:47 joel Exp $
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include <assert.h>
#include <errno.h>
#include <pthread.h>

#include <rtems/system.h>
#include <rtems/score/coremutex.h>
#include <rtems/score/watchdog.h>
#if defined(RTEMS_MULTIPROCESSING)
#include <rtems/score/mpci.h>
#endif
#include <rtems/posix/mutex.h>
#include <rtems/posix/priority.h>
#include <rtems/posix/time.h>

/*PAGE
 *
 *  11.3.2 Initializing and Destroying a Mutex, P1003.1c/Draft 10, p. 87
 *
 *  NOTE:  XXX Could be optimized so all the attribute error checking
 *             is not performed when attr is NULL.
 */

int pthread_mutex_init(
  pthread_mutex_t           *mutex,
  const pthread_mutexattr_t *attr
)
{
  POSIX_Mutex_Control          *the_mutex;
  CORE_mutex_Attributes        *the_mutex_attr;
  const pthread_mutexattr_t    *the_attr;
  CORE_mutex_Disciplines        the_discipline;
#if 0
  register POSIX_Mutex_Control *mutex_in_use;
  Objects_Locations             location;
#endif

  if ( attr ) the_attr = attr;
  else        the_attr = &_POSIX_Mutex_Default_attributes;

  /* Check for NULL mutex */

  if ( !mutex )
    return EINVAL;

  /*
   *  This code should eventually be removed.  
   *
   *  Although the POSIX specification says:
   *
   *  "Attempting to initialize an already initialized mutex results
   *  in undefined behavior."
   *
   *  Trying to keep the caller from doing the create when *mutex
   *  is actually a valid ID causes grief.  All it takes is the wrong
   *  value in an uninitialized variable to make this fail.  As best
   *  I can tell, RTEMS was the only pthread implementation to choose
   *  this option for "undefined behavior" and doing so has created
   *  portability problems.  In particular, Rosimildo DaSilva
   *  <[e-mail]> saw seemingly random failures in the
   *  RTEMS port of omniORB2 when this code was enabled.
   *
   *  Joel Sherrill <[e-mail]>     14 May 1999
   */

  
#if 0
  /* avoid infinite recursion on call to this routine in _POSIX_Mutex_Get */

  if ( *mutex != PTHREAD_MUTEX_INITIALIZER ) {

    /* EBUSY if *mutex is a valid id */

    mutex_in_use = _POSIX_Mutex_Get( mutex, &location );
    switch ( location ) {
      case OBJECTS_REMOTE:
      case OBJECTS_ERROR:
        break;
      case OBJECTS_LOCAL:
        _Thread_Enable_dispatch();
        return EBUSY;
    }
  }
#endif
 
  if ( !the_attr->is_initialized ) 
    return EINVAL;

  /*
   *  XXX: Be careful about attributes when global!!!
   */

  assert( the_attr->process_shared == PTHREAD_PROCESS_PRIVATE );

#if defined(RTEMS_MULTIPROCESSING)
  if ( the_attr->process_shared == PTHREAD_PROCESS_SHARED )
    return POSIX_MP_NOT_IMPLEMENTED();
#endif
 
  /*
   *  Determine the discipline of the mutex
   */
  
  switch ( the_attr->protocol ) {
    case PTHREAD_PRIO_NONE:
      the_discipline = CORE_MUTEX_DISCIPLINES_FIFO;
      break;
    case PTHREAD_PRIO_INHERIT:
      the_discipline = CORE_MUTEX_DISCIPLINES_PRIORITY_INHERIT;
      break;
    case PTHREAD_PRIO_PROTECT:
      the_discipline = CORE_MUTEX_DISCIPLINES_PRIORITY_CEILING;
      break;
    default:
      return EINVAL;
  }

  if ( !_POSIX_Priority_Is_valid( the_attr->prio_ceiling ) )
    return EINVAL;

  _Thread_Disable_dispatch();

  the_mutex = _POSIX_Mutex_Allocate();
 
  if ( !the_mutex ) {
    _Thread_Enable_dispatch();
    return EAGAIN;
  }

#if defined(RTEMS_MULTIPROCESSING)
  if ( the_attr->process_shared == PTHREAD_PROCESS_SHARED && 
       !( _Objects_MP_Allocate_and_open( &_POSIX_Mutex_Information, 0,
                            the_mutex->Object.id, FALSE ) ) ) {
    _POSIX_Mutex_Free( the_mutex );
    _Thread_Enable_dispatch();
    return EAGAIN;
  }
#endif

  the_mutex->process_shared = the_attr->process_shared;

  the_mutex_attr = &the_mutex->Mutex.Attributes;

  if ( the_attr->recursive )
    the_mutex_attr->lock_nesting_behavior = CORE_MUTEX_NESTING_ACQUIRES;
  else
    the_mutex_attr->lock_nesting_behavior = CORE_MUTEX_NESTING_IS_ERROR;
  the_mutex_attr->only_owner_release = TRUE;
  the_mutex_attr->priority_ceiling =
    _POSIX_Priority_To_core( the_attr->prio_ceiling );
  the_mutex_attr->discipline = the_discipline;

  /*
   *  Must be initialized to unlocked.
   */

  _CORE_mutex_Initialize(
    &the_mutex->Mutex,
    the_mutex_attr,
    CORE_MUTEX_UNLOCKED
  );

  _Objects_Open( &_POSIX_Mutex_Information, &the_mutex->Object, 0 );

  *mutex = the_mutex->Object.id;

#if defined(RTEMS_MULTIPROCESSING)
  if ( the_attr->process_shared == PTHREAD_PROCESS_SHARED )
    _POSIX_Mutex_MP_Send_process_packet(
      POSIX_MUTEX_MP_ANNOUNCE_CREATE,
      the_mutex->Object.id,
      0,                         /* Name not used */
      0                          /* Not used */
    );
#endif

  _Thread_Enable_dispatch();
  return 0;
}