dbus/dbus/dbus-threads.c - nest-cam/4320010/dbus - Git at Google

 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
 /* dbus-threads.h  D-Bus threads handling
  *
  * Copyright (C) 2002, 2003, 2006 Red Hat Inc.
  *
  * Licensed under the Academic Free License version 2.1
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  *
  */
 #include <config.h>
 #include "dbus-threads.h"
 #include "dbus-internals.h"
 #include "dbus-threads-internal.h"
 #include "dbus-list.h"

 static int thread_init_generation = 0;

 static DBusList *uninitialized_rmutex_list = NULL;
 static DBusList *uninitialized_cmutex_list = NULL;
 static DBusList *uninitialized_condvar_list = NULL;

 /** This is used for the no-op default mutex pointer, just to be distinct from #NULL */
 #define _DBUS_DUMMY_MUTEX ((DBusMutex*)0xABCDEF)
 #define _DBUS_DUMMY_RMUTEX ((DBusRMutex *) _DBUS_DUMMY_MUTEX)
 #define _DBUS_DUMMY_CMUTEX ((DBusCMutex *) _DBUS_DUMMY_MUTEX)

 /** This is used for the no-op default mutex pointer, just to be distinct from #NULL */
 #define _DBUS_DUMMY_CONDVAR ((DBusCondVar*)0xABCDEF2)

 /**
  * @defgroup DBusThreadsInternals Thread functions
  * @ingroup  DBusInternals
  * @brief _dbus_rmutex_lock(), etc.
  *
  * Functions and macros related to threads and thread locks.
  *
  * @{
  */

 /**
  * Creates a new mutex
  * or creates a no-op mutex if threads are not initialized.
  * May return #NULL even if threads are initialized, indicating
  * out-of-memory.
  *
  * If possible, the mutex returned by this function is recursive, to
  * avoid deadlocks. However, that cannot be relied on.
  *
  * The extra level of indirection given by allocating a pointer
  * to point to the mutex location allows the threading
  * module to swap out dummy mutexes for a real mutex so libraries
  * can initialize threads even after the D-Bus API has been used.
  *
  * @param location_p the location of the new mutex, can return #NULL on OOM
  */
 void
 _dbus_rmutex_new_at_location (DBusRMutex **location_p)
 {
   _dbus_assert (location_p != NULL);

   if (thread_init_generation == _dbus_current_generation)
     {
       *location_p = _dbus_platform_rmutex_new ();
     }
   else
     {
       *location_p = _DBUS_DUMMY_RMUTEX;

       if (!_dbus_list_append (&uninitialized_rmutex_list, location_p))
         *location_p = NULL;
     }
 }

 /**
  * Creates a new mutex
  * or creates a no-op mutex if threads are not initialized.
  * May return #NULL even if threads are initialized, indicating
  * out-of-memory.
  *
  * The returned mutex is suitable for use with condition variables.
  *
  * The extra level of indirection given by allocating a pointer
  * to point to the mutex location allows the threading
  * module to swap out dummy mutexes for a real mutex so libraries
  * can initialize threads even after the D-Bus API has been used.
  *
  * @param location_p the location of the new mutex, can return #NULL on OOM
  */
 void
 _dbus_cmutex_new_at_location (DBusCMutex **location_p)
 {
   _dbus_assert (location_p != NULL);

   if (thread_init_generation == _dbus_current_generation)
     {
       *location_p = _dbus_platform_cmutex_new ();
     }
   else
     {
       *location_p = _DBUS_DUMMY_CMUTEX;

       if (!_dbus_list_append (&uninitialized_cmutex_list, location_p))
         *location_p = NULL;
     }
 }

 /**
  * Frees a DBusRMutex or removes it from the uninitialized mutex list;
  * does nothing if passed a #NULL pointer.
  */
 void
 _dbus_rmutex_free_at_location (DBusRMutex **location_p)
 {
   if (location_p == NULL)
     return;

   if (thread_init_generation == _dbus_current_generation)
     {
       if (*location_p != NULL)
         _dbus_platform_rmutex_free (*location_p);
     }
   else
     {
       _dbus_assert (*location_p == NULL || *location_p == _DBUS_DUMMY_RMUTEX);

       _dbus_list_remove (&uninitialized_rmutex_list, location_p);
     }
 }

 /**
  * Frees a DBusCMutex and removes it from the
  * uninitialized mutex list;
  * does nothing if passed a #NULL pointer.
  */
 void
 _dbus_cmutex_free_at_location (DBusCMutex **location_p)
 {
   if (location_p == NULL)
     return;

   if (thread_init_generation == _dbus_current_generation)
     {
       if (*location_p != NULL)
         _dbus_platform_cmutex_free (*location_p);
     }
   else
     {
       _dbus_assert (*location_p == NULL || *location_p == _DBUS_DUMMY_CMUTEX);

       _dbus_list_remove (&uninitialized_cmutex_list, location_p);
     }
 }

 /**
  * Locks a mutex. Does nothing if passed a #NULL pointer.
  * Locks may be recursive if threading implementation initialized
  * recursive locks.
  */
 void
 _dbus_rmutex_lock (DBusRMutex *mutex)
 {
   if (mutex && thread_init_generation == _dbus_current_generation)
     _dbus_platform_rmutex_lock (mutex);
 }

 /**
  * Locks a mutex. Does nothing if passed a #NULL pointer.
  * Locks may be recursive if threading implementation initialized
  * recursive locks.
  */
 void
 _dbus_cmutex_lock (DBusCMutex *mutex)
 {
   if (mutex && thread_init_generation == _dbus_current_generation)
     _dbus_platform_cmutex_lock (mutex);
 }

 /**
  * Unlocks a mutex. Does nothing if passed a #NULL pointer.
  *
  * @returns #TRUE on success
  */
 void
 _dbus_rmutex_unlock (DBusRMutex *mutex)
 {
   if (mutex && thread_init_generation == _dbus_current_generation)
     _dbus_platform_rmutex_unlock (mutex);
 }

 /**
  * Unlocks a mutex. Does nothing if passed a #NULL pointer.
  *
  * @returns #TRUE on success
  */
 void
 _dbus_cmutex_unlock (DBusCMutex *mutex)
 {
   if (mutex && thread_init_generation == _dbus_current_generation)
     _dbus_platform_cmutex_unlock (mutex);
 }

 /**
  * Creates a new condition variable using the function supplied
  * to dbus_threads_init(), or creates a no-op condition variable
  * if threads are not initialized. May return #NULL even if
  * threads are initialized, indicating out-of-memory.
  *
  * @returns new mutex or #NULL
  */
 DBusCondVar *
 _dbus_condvar_new (void)
 {
   if (thread_init_generation == _dbus_current_generation)
     return _dbus_platform_condvar_new ();
   else
     return _DBUS_DUMMY_CONDVAR;
 }


 /**
  * This does the same thing as _dbus_condvar_new.  It however
  * gives another level of indirection by allocating a pointer
  * to point to the condvar location.  This allows the threading
  * module to swap out dummy condvars for a real condvar so libraries
  * can initialize threads even after the D-Bus API has been used.
  *
  * @returns the location of a new condvar or #NULL on OOM
  */

 void
 _dbus_condvar_new_at_location (DBusCondVar **location_p)
 {
   _dbus_assert (location_p != NULL);

   if (thread_init_generation == _dbus_current_generation)
     {
       *location_p = _dbus_condvar_new();
     }
   else
     {
       *location_p = _DBUS_DUMMY_CONDVAR;

       if (!_dbus_list_append (&uninitialized_condvar_list, location_p))
         *location_p = NULL;
     }
 }


 /**
  * Frees a conditional variable created with dbus_condvar_new(); does
  * nothing if passed a #NULL pointer.
  */
 void
 _dbus_condvar_free (DBusCondVar *cond)
 {
   if (cond && thread_init_generation == _dbus_current_generation)
     _dbus_platform_condvar_free (cond);
 }

 /**
  * Frees a conditional variable and removes it from the
  * uninitialized_condvar_list;
  * does nothing if passed a #NULL pointer.
  */
 void
 _dbus_condvar_free_at_location (DBusCondVar **location_p)
 {
   if (location_p == NULL)
     return;

   if (thread_init_generation == _dbus_current_generation)
     {
       if (*location_p != NULL)
         _dbus_platform_condvar_free (*location_p);
     }
   else
     {
       _dbus_assert (*location_p == NULL || *location_p == _DBUS_DUMMY_CONDVAR);

       _dbus_list_remove (&uninitialized_condvar_list, location_p);
     }
 }

 /**
  * Atomically unlocks the mutex and waits for the conditions
  * variable to be signalled. Locks the mutex again before
  * returning.
  * Does nothing if passed a #NULL pointer.
  */
 void
 _dbus_condvar_wait (DBusCondVar *cond,
                     DBusCMutex  *mutex)
 {
   if (cond && mutex && thread_init_generation == _dbus_current_generation)
     _dbus_platform_condvar_wait (cond, mutex);
 }

 /**
  * Atomically unlocks the mutex and waits for the conditions variable
  * to be signalled, or for a timeout. Locks the mutex again before
  * returning.  Does nothing if passed a #NULL pointer.  Return value
  * is #FALSE if we timed out, #TRUE otherwise.
  *
  * @param cond the condition variable
  * @param mutex the mutex
  * @param timeout_milliseconds the maximum time to wait
  * @returns #FALSE if the timeout occurred, #TRUE if not
  */
 dbus_bool_t
 _dbus_condvar_wait_timeout (DBusCondVar               *cond,
                             DBusCMutex                *mutex,
                             int                        timeout_milliseconds)
 {
   if (cond && mutex && thread_init_generation == _dbus_current_generation)
     return _dbus_platform_condvar_wait_timeout (cond, mutex,
                                                 timeout_milliseconds);
   else
     return TRUE;
 }

 /**
  * If there are threads waiting on the condition variable, wake
  * up exactly one.
  * Does nothing if passed a #NULL pointer.
  */
 void
 _dbus_condvar_wake_one (DBusCondVar *cond)
 {
   if (cond && thread_init_generation == _dbus_current_generation)
     _dbus_platform_condvar_wake_one (cond);
 }

 static void
 shutdown_global_locks (void *data)
 {
   DBusRMutex ***locks = data;
   int i;

   i = 0;
   while (i < _DBUS_N_GLOBAL_LOCKS)
     {
       if (*(locks[i]) != NULL)
         _dbus_platform_rmutex_free (*(locks[i]));

       *(locks[i]) = NULL;
       ++i;
     }

   dbus_free (locks);
 }

 static void
 shutdown_uninitialized_locks (void *data)
 {
   _dbus_list_clear (&uninitialized_rmutex_list);
   _dbus_list_clear (&uninitialized_cmutex_list);
   _dbus_list_clear (&uninitialized_condvar_list);
 }

 static dbus_bool_t
 init_uninitialized_locks (void)
 {
   DBusList *link;

   _dbus_assert (thread_init_generation != _dbus_current_generation);

   link = uninitialized_rmutex_list;
   while (link != NULL)
     {
       DBusRMutex **mp;

       mp = link->data;
       _dbus_assert (*mp == _DBUS_DUMMY_RMUTEX);

       *mp = _dbus_platform_rmutex_new ();
       if (*mp == NULL)
         goto fail_mutex;

       link = _dbus_list_get_next_link (&uninitialized_rmutex_list, link);
     }

   link = uninitialized_cmutex_list;
   while (link != NULL)
     {
       DBusCMutex **mp;

       mp = link->data;
       _dbus_assert (*mp == _DBUS_DUMMY_CMUTEX);

       *mp = _dbus_platform_cmutex_new ();
       if (*mp == NULL)
         goto fail_mutex;

       link = _dbus_list_get_next_link (&uninitialized_cmutex_list, link);
     }

   link = uninitialized_condvar_list;
   while (link != NULL)
     {
       DBusCondVar **cp;

       cp = (DBusCondVar **)link->data;
       _dbus_assert (*cp == _DBUS_DUMMY_CONDVAR);

       *cp = _dbus_platform_condvar_new ();
       if (*cp == NULL)
         goto fail_condvar;

       link = _dbus_list_get_next_link (&uninitialized_condvar_list, link);
     }

   _dbus_list_clear (&uninitialized_rmutex_list);
   _dbus_list_clear (&uninitialized_cmutex_list);
   _dbus_list_clear (&uninitialized_condvar_list);

   if (!_dbus_register_shutdown_func (shutdown_uninitialized_locks,
                                      NULL))
     goto fail_condvar;

   return TRUE;

  fail_condvar:
   link = uninitialized_condvar_list;
   while (link != NULL)
     {
       DBusCondVar **cp;

       cp = link->data;

       if (*cp != _DBUS_DUMMY_CONDVAR && *cp != NULL)
         _dbus_platform_condvar_free (*cp);

       *cp = _DBUS_DUMMY_CONDVAR;

       link = _dbus_list_get_next_link (&uninitialized_condvar_list, link);
     }

  fail_mutex:
   link = uninitialized_rmutex_list;
   while (link != NULL)
     {
       DBusRMutex **mp;

       mp = link->data;

       if (*mp != _DBUS_DUMMY_RMUTEX && *mp != NULL)
         _dbus_platform_rmutex_free (*mp);

       *mp = _DBUS_DUMMY_RMUTEX;

       link = _dbus_list_get_next_link (&uninitialized_rmutex_list, link);
     }

   link = uninitialized_cmutex_list;
   while (link != NULL)
     {
       DBusCMutex **mp;

       mp = link->data;

       if (*mp != _DBUS_DUMMY_CMUTEX && *mp != NULL)
         _dbus_platform_cmutex_free (*mp);

       *mp = _DBUS_DUMMY_CMUTEX;

       link = _dbus_list_get_next_link (&uninitialized_cmutex_list, link);
     }

   return FALSE;
 }

 static dbus_bool_t
 init_locks (void)
 {
   int i;
   DBusRMutex ***dynamic_global_locks;
   DBusRMutex **global_locks[] = {
 #define LOCK_ADDR(name) (& _dbus_lock_##name)
     LOCK_ADDR (win_fds),
     LOCK_ADDR (sid_atom_cache),
     LOCK_ADDR (list),
     LOCK_ADDR (connection_slots),
     LOCK_ADDR (pending_call_slots),
     LOCK_ADDR (server_slots),
     LOCK_ADDR (message_slots),
 #if !DBUS_USE_SYNC
     LOCK_ADDR (atomic),
 #endif
     LOCK_ADDR (bus),
     LOCK_ADDR (bus_datas),
     LOCK_ADDR (shutdown_funcs),
     LOCK_ADDR (system_users),
     LOCK_ADDR (message_cache),
     LOCK_ADDR (shared_connections),
     LOCK_ADDR (machine_uuid)
 #undef LOCK_ADDR
   };

   _dbus_assert (_DBUS_N_ELEMENTS (global_locks) ==
                 _DBUS_N_GLOBAL_LOCKS);

   i = 0;

   dynamic_global_locks = dbus_new (DBusRMutex**, _DBUS_N_GLOBAL_LOCKS);
   if (dynamic_global_locks == NULL)
     goto failed;

   while (i < _DBUS_N_ELEMENTS (global_locks))
     {
       *global_locks[i] = _dbus_platform_rmutex_new ();

       if (*global_locks[i] == NULL)
         goto failed;

       dynamic_global_locks[i] = global_locks[i];

       ++i;
     }

   if (!_dbus_register_shutdown_func (shutdown_global_locks,
                                      dynamic_global_locks))
     goto failed;

   if (!init_uninitialized_locks ())
     goto failed;

   return TRUE;

  failed:
   dbus_free (dynamic_global_locks);

   for (i = i - 1; i >= 0; i--)
     {
       _dbus_platform_rmutex_free (*global_locks[i]);
       *global_locks[i] = NULL;
     }
   return FALSE;
 }

 /** @} */ /* end of internals */

 /**
  * @defgroup DBusThreads Thread functions
  * @ingroup  DBus
  * @brief dbus_threads_init() and dbus_threads_init_default()
  *
  * Functions and macros related to threads and thread locks.
  *
  * If threads are initialized, the D-Bus library has locks on all
  * global data structures.  In addition, each #DBusConnection has a
  * lock, so only one thread at a time can touch the connection.  (See
  * @ref DBusConnection for more on connection locking.)
  *
  * Most other objects, however, do not have locks - they can only be
  * used from a single thread at a time, unless you lock them yourself.
  * For example, a #DBusMessage can't be modified from two threads
  * at once.
  *
  * @{
  */

 /**
  * Initializes threads, like dbus_threads_init_default().
  * This version previously allowed user-specified threading
  * primitives, but since D-Bus 1.6 it ignores them and behaves
  * exactly like dbus_threads_init_default().
  *
  * @param functions ignored, formerly functions for using threads
  * @returns #TRUE on success, #FALSE if no memory
  */
 dbus_bool_t
 dbus_threads_init (const DBusThreadFunctions *functions)
 {
   if (thread_init_generation == _dbus_current_generation)
     return TRUE;

   if (!init_locks ())
     return FALSE;

   thread_init_generation = _dbus_current_generation;

   return TRUE;
 }


 /* Default thread implemenation */

 /**
  * Initializes threads. If this function is not called, the D-Bus
  * library will not lock any data structures.  If it is called, D-Bus
  * will do locking, at some cost in efficiency. Note that this
  * function must be called BEFORE the second thread is started.
  *
  * It's safe to call dbus_threads_init_default() as many times as you
  * want, but only the first time will have an effect.
  *
  * dbus_shutdown() reverses the effects of this function when it
  * resets all global state in libdbus.
  *
  * @returns #TRUE on success, #FALSE if not enough memory
  */
 dbus_bool_t
 dbus_threads_init_default (void)
 {
   return _dbus_threads_init_platform_specific ();
 }


 /** @} */

 #ifdef DBUS_BUILD_TESTS

 dbus_bool_t
 _dbus_threads_init_debug (void)
 {
   return _dbus_threads_init_platform_specific();
 }

 #endif /* DBUS_BUILD_TESTS */
	/* -- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -- */
	/* dbus-threads.h D-Bus threads handling
	*
	* Copyright (C) 2002, 2003, 2006 Red Hat Inc.
	*
	* Licensed under the Academic Free License version 2.1
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*
	*/
	#include <config.h>
	#include "dbus-threads.h"
	#include "dbus-internals.h"
	#include "dbus-threads-internal.h"
	#include "dbus-list.h"

	static int thread_init_generation = 0;

	static DBusList *uninitialized_rmutex_list = NULL;
	static DBusList *uninitialized_cmutex_list = NULL;
	static DBusList *uninitialized_condvar_list = NULL;

	/** This is used for the no-op default mutex pointer, just to be distinct from #NULL */
	#define _DBUS_DUMMY_MUTEX ((DBusMutex*)0xABCDEF)
	#define _DBUS_DUMMY_RMUTEX ((DBusRMutex *) _DBUS_DUMMY_MUTEX)
	#define _DBUS_DUMMY_CMUTEX ((DBusCMutex *) _DBUS_DUMMY_MUTEX)

	/** This is used for the no-op default mutex pointer, just to be distinct from #NULL */
	#define _DBUS_DUMMY_CONDVAR ((DBusCondVar*)0xABCDEF2)

	/**
	* @defgroup DBusThreadsInternals Thread functions
	* @ingroup DBusInternals
	* @brief _dbus_rmutex_lock(), etc.
	*
	* Functions and macros related to threads and thread locks.
	*
	* @{
	*/

	/**
	* Creates a new mutex
	* or creates a no-op mutex if threads are not initialized.
	* May return #NULL even if threads are initialized, indicating
	* out-of-memory.
	*
	* If possible, the mutex returned by this function is recursive, to
	* avoid deadlocks. However, that cannot be relied on.
	*
	* The extra level of indirection given by allocating a pointer
	* to point to the mutex location allows the threading
	* module to swap out dummy mutexes for a real mutex so libraries
	* can initialize threads even after the D-Bus API has been used.
	*
	* @param location_p the location of the new mutex, can return #NULL on OOM
	*/
	void
	_dbus_rmutex_new_at_location (DBusRMutex **location_p)
	{
	_dbus_assert (location_p != NULL);

	if (thread_init_generation == _dbus_current_generation)
	{
	*location_p = _dbus_platform_rmutex_new ();
	}
	else
	{
	*location_p = _DBUS_DUMMY_RMUTEX;

	if (!_dbus_list_append (&uninitialized_rmutex_list, location_p))
	*location_p = NULL;
	}
	}

	/**
	* Creates a new mutex
	* or creates a no-op mutex if threads are not initialized.
	* May return #NULL even if threads are initialized, indicating
	* out-of-memory.
	*
	* The returned mutex is suitable for use with condition variables.
	*
	* The extra level of indirection given by allocating a pointer
	* to point to the mutex location allows the threading
	* module to swap out dummy mutexes for a real mutex so libraries
	* can initialize threads even after the D-Bus API has been used.
	*
	* @param location_p the location of the new mutex, can return #NULL on OOM
	*/
	void
	_dbus_cmutex_new_at_location (DBusCMutex **location_p)
	{
	_dbus_assert (location_p != NULL);

	if (thread_init_generation == _dbus_current_generation)
	{
	*location_p = _dbus_platform_cmutex_new ();
	}
	else
	{
	*location_p = _DBUS_DUMMY_CMUTEX;

	if (!_dbus_list_append (&uninitialized_cmutex_list, location_p))
	*location_p = NULL;
	}
	}

	/**
	* Frees a DBusRMutex or removes it from the uninitialized mutex list;
	* does nothing if passed a #NULL pointer.
	*/
	void
	_dbus_rmutex_free_at_location (DBusRMutex **location_p)
	{
	if (location_p == NULL)
	return;

	if (thread_init_generation == _dbus_current_generation)
	{
	if (*location_p != NULL)
	_dbus_platform_rmutex_free (*location_p);
	}
	else
	{
	_dbus_assert (location_p == NULL \|\| location_p == _DBUS_DUMMY_RMUTEX);

	_dbus_list_remove (&uninitialized_rmutex_list, location_p);
	}
	}

	/**
	* Frees a DBusCMutex and removes it from the
	* uninitialized mutex list;
	* does nothing if passed a #NULL pointer.
	*/
	void
	_dbus_cmutex_free_at_location (DBusCMutex **location_p)
	{
	if (location_p == NULL)
	return;

	if (thread_init_generation == _dbus_current_generation)
	{
	if (*location_p != NULL)
	_dbus_platform_cmutex_free (*location_p);
	}
	else
	{
	_dbus_assert (location_p == NULL \|\| location_p == _DBUS_DUMMY_CMUTEX);

	_dbus_list_remove (&uninitialized_cmutex_list, location_p);
	}
	}

	/**
	* Locks a mutex. Does nothing if passed a #NULL pointer.
	* Locks may be recursive if threading implementation initialized
	* recursive locks.
	*/
	void
	_dbus_rmutex_lock (DBusRMutex *mutex)
	{
	if (mutex && thread_init_generation == _dbus_current_generation)
	_dbus_platform_rmutex_lock (mutex);
	}

	/**
	* Locks a mutex. Does nothing if passed a #NULL pointer.
	* Locks may be recursive if threading implementation initialized
	* recursive locks.
	*/
	void
	_dbus_cmutex_lock (DBusCMutex *mutex)
	{
	if (mutex && thread_init_generation == _dbus_current_generation)
	_dbus_platform_cmutex_lock (mutex);
	}

	/**
	* Unlocks a mutex. Does nothing if passed a #NULL pointer.
	*
	* @returns #TRUE on success
	*/
	void
	_dbus_rmutex_unlock (DBusRMutex *mutex)
	{
	if (mutex && thread_init_generation == _dbus_current_generation)
	_dbus_platform_rmutex_unlock (mutex);
	}

	/**
	* Unlocks a mutex. Does nothing if passed a #NULL pointer.
	*
	* @returns #TRUE on success
	*/
	void
	_dbus_cmutex_unlock (DBusCMutex *mutex)
	{
	if (mutex && thread_init_generation == _dbus_current_generation)
	_dbus_platform_cmutex_unlock (mutex);
	}

	/**
	* Creates a new condition variable using the function supplied
	* to dbus_threads_init(), or creates a no-op condition variable
	* if threads are not initialized. May return #NULL even if
	* threads are initialized, indicating out-of-memory.
	*
	* @returns new mutex or #NULL
	*/
	DBusCondVar *
	_dbus_condvar_new (void)
	{
	if (thread_init_generation == _dbus_current_generation)
	return _dbus_platform_condvar_new ();
	else
	return _DBUS_DUMMY_CONDVAR;
	}


	/**
	* This does the same thing as _dbus_condvar_new. It however
	* gives another level of indirection by allocating a pointer
	* to point to the condvar location. This allows the threading
	* module to swap out dummy condvars for a real condvar so libraries
	* can initialize threads even after the D-Bus API has been used.
	*
	* @returns the location of a new condvar or #NULL on OOM
	*/

	void
	_dbus_condvar_new_at_location (DBusCondVar **location_p)
	{
	_dbus_assert (location_p != NULL);

	if (thread_init_generation == _dbus_current_generation)
	{
	*location_p = _dbus_condvar_new();
	}
	else
	{
	*location_p = _DBUS_DUMMY_CONDVAR;

	if (!_dbus_list_append (&uninitialized_condvar_list, location_p))
	*location_p = NULL;
	}
	}


	/**
	* Frees a conditional variable created with dbus_condvar_new(); does
	* nothing if passed a #NULL pointer.
	*/
	void
	_dbus_condvar_free (DBusCondVar *cond)
	{
	if (cond && thread_init_generation == _dbus_current_generation)
	_dbus_platform_condvar_free (cond);
	}

	/**
	* Frees a conditional variable and removes it from the
	* uninitialized_condvar_list;
	* does nothing if passed a #NULL pointer.
	*/
	void
	_dbus_condvar_free_at_location (DBusCondVar **location_p)
	{
	if (location_p == NULL)
	return;

	if (thread_init_generation == _dbus_current_generation)
	{
	if (*location_p != NULL)
	_dbus_platform_condvar_free (*location_p);
	}
	else
	{
	_dbus_assert (location_p == NULL \|\| location_p == _DBUS_DUMMY_CONDVAR);

	_dbus_list_remove (&uninitialized_condvar_list, location_p);
	}
	}

	/**
	* Atomically unlocks the mutex and waits for the conditions
	* variable to be signalled. Locks the mutex again before
	* returning.
	* Does nothing if passed a #NULL pointer.
	*/
	void
	_dbus_condvar_wait (DBusCondVar *cond,
	DBusCMutex *mutex)
	{
	if (cond && mutex && thread_init_generation == _dbus_current_generation)
	_dbus_platform_condvar_wait (cond, mutex);
	}

	/**
	* Atomically unlocks the mutex and waits for the conditions variable
	* to be signalled, or for a timeout. Locks the mutex again before
	* returning. Does nothing if passed a #NULL pointer. Return value
	* is #FALSE if we timed out, #TRUE otherwise.
	*
	* @param cond the condition variable
	* @param mutex the mutex
	* @param timeout_milliseconds the maximum time to wait
	* @returns #FALSE if the timeout occurred, #TRUE if not
	*/
	dbus_bool_t
	_dbus_condvar_wait_timeout (DBusCondVar *cond,
	DBusCMutex *mutex,
	int timeout_milliseconds)
	{
	if (cond && mutex && thread_init_generation == _dbus_current_generation)
	return _dbus_platform_condvar_wait_timeout (cond, mutex,
	timeout_milliseconds);
	else
	return TRUE;
	}

	/**
	* If there are threads waiting on the condition variable, wake
	* up exactly one.
	* Does nothing if passed a #NULL pointer.
	*/
	void
	_dbus_condvar_wake_one (DBusCondVar *cond)
	{
	if (cond && thread_init_generation == _dbus_current_generation)
	_dbus_platform_condvar_wake_one (cond);
	}

	static void
	shutdown_global_locks (void *data)
	{
	DBusRMutex ***locks = data;
	int i;

	i = 0;
	while (i < _DBUS_N_GLOBAL_LOCKS)
	{
	if (*(locks[i]) != NULL)
	_dbus_platform_rmutex_free (*(locks[i]));

	*(locks[i]) = NULL;
	++i;
	}

	dbus_free (locks);
	}

	static void
	shutdown_uninitialized_locks (void *data)
	{
	_dbus_list_clear (&uninitialized_rmutex_list);
	_dbus_list_clear (&uninitialized_cmutex_list);
	_dbus_list_clear (&uninitialized_condvar_list);
	}

	static dbus_bool_t
	init_uninitialized_locks (void)
	{
	DBusList *link;

	_dbus_assert (thread_init_generation != _dbus_current_generation);

	link = uninitialized_rmutex_list;
	while (link != NULL)
	{
	DBusRMutex **mp;

	mp = link->data;
	_dbus_assert (*mp == _DBUS_DUMMY_RMUTEX);

	*mp = _dbus_platform_rmutex_new ();
	if (*mp == NULL)
	goto fail_mutex;

	link = _dbus_list_get_next_link (&uninitialized_rmutex_list, link);
	}

	link = uninitialized_cmutex_list;
	while (link != NULL)
	{
	DBusCMutex **mp;

	mp = link->data;
	_dbus_assert (*mp == _DBUS_DUMMY_CMUTEX);

	*mp = _dbus_platform_cmutex_new ();
	if (*mp == NULL)
	goto fail_mutex;

	link = _dbus_list_get_next_link (&uninitialized_cmutex_list, link);
	}

	link = uninitialized_condvar_list;
	while (link != NULL)
	{
	DBusCondVar **cp;

	cp = (DBusCondVar **)link->data;
	_dbus_assert (*cp == _DBUS_DUMMY_CONDVAR);

	*cp = _dbus_platform_condvar_new ();
	if (*cp == NULL)
	goto fail_condvar;

	link = _dbus_list_get_next_link (&uninitialized_condvar_list, link);
	}

	_dbus_list_clear (&uninitialized_rmutex_list);
	_dbus_list_clear (&uninitialized_cmutex_list);
	_dbus_list_clear (&uninitialized_condvar_list);

	if (!_dbus_register_shutdown_func (shutdown_uninitialized_locks,
	NULL))
	goto fail_condvar;

	return TRUE;

	fail_condvar:
	link = uninitialized_condvar_list;
	while (link != NULL)
	{
	DBusCondVar **cp;

	cp = link->data;

	if (cp != _DBUS_DUMMY_CONDVAR && cp != NULL)
	_dbus_platform_condvar_free (*cp);

	*cp = _DBUS_DUMMY_CONDVAR;

	link = _dbus_list_get_next_link (&uninitialized_condvar_list, link);
	}

	fail_mutex:
	link = uninitialized_rmutex_list;
	while (link != NULL)
	{
	DBusRMutex **mp;

	mp = link->data;

	if (mp != _DBUS_DUMMY_RMUTEX && mp != NULL)
	_dbus_platform_rmutex_free (*mp);

	*mp = _DBUS_DUMMY_RMUTEX;

	link = _dbus_list_get_next_link (&uninitialized_rmutex_list, link);
	}

	link = uninitialized_cmutex_list;
	while (link != NULL)
	{
	DBusCMutex **mp;

	mp = link->data;

	if (mp != _DBUS_DUMMY_CMUTEX && mp != NULL)
	_dbus_platform_cmutex_free (*mp);

	*mp = _DBUS_DUMMY_CMUTEX;

	link = _dbus_list_get_next_link (&uninitialized_cmutex_list, link);
	}

	return FALSE;
	}

	static dbus_bool_t
	init_locks (void)
	{
	int i;
	DBusRMutex ***dynamic_global_locks;
	DBusRMutex **global_locks[] = {
	#define LOCK_ADDR(name) (& _dbus_lock_##name)
	LOCK_ADDR (win_fds),
	LOCK_ADDR (sid_atom_cache),
	LOCK_ADDR (list),
	LOCK_ADDR (connection_slots),
	LOCK_ADDR (pending_call_slots),
	LOCK_ADDR (server_slots),
	LOCK_ADDR (message_slots),
	#if !DBUS_USE_SYNC
	LOCK_ADDR (atomic),
	#endif
	LOCK_ADDR (bus),
	LOCK_ADDR (bus_datas),
	LOCK_ADDR (shutdown_funcs),
	LOCK_ADDR (system_users),
	LOCK_ADDR (message_cache),
	LOCK_ADDR (shared_connections),
	LOCK_ADDR (machine_uuid)
	#undef LOCK_ADDR
	};

	_dbus_assert (_DBUS_N_ELEMENTS (global_locks) ==
	_DBUS_N_GLOBAL_LOCKS);

	i = 0;

	dynamic_global_locks = dbus_new (DBusRMutex**, _DBUS_N_GLOBAL_LOCKS);
	if (dynamic_global_locks == NULL)
	goto failed;

	while (i < _DBUS_N_ELEMENTS (global_locks))
	{
	*global_locks[i] = _dbus_platform_rmutex_new ();

	if (*global_locks[i] == NULL)
	goto failed;

	dynamic_global_locks[i] = global_locks[i];

	++i;
	}

	if (!_dbus_register_shutdown_func (shutdown_global_locks,
	dynamic_global_locks))
	goto failed;

	if (!init_uninitialized_locks ())
	goto failed;

	return TRUE;

	failed:
	dbus_free (dynamic_global_locks);

	for (i = i - 1; i >= 0; i--)
	{
	_dbus_platform_rmutex_free (*global_locks[i]);
	*global_locks[i] = NULL;
	}
	return FALSE;
	}

	/** @} / / end of internals */

	/**
	* @defgroup DBusThreads Thread functions
	* @ingroup DBus
	* @brief dbus_threads_init() and dbus_threads_init_default()
	*
	* Functions and macros related to threads and thread locks.
	*
	* If threads are initialized, the D-Bus library has locks on all
	* global data structures. In addition, each #DBusConnection has a
	* lock, so only one thread at a time can touch the connection. (See
	* @ref DBusConnection for more on connection locking.)
	*
	* Most other objects, however, do not have locks - they can only be
	* used from a single thread at a time, unless you lock them yourself.
	* For example, a #DBusMessage can't be modified from two threads
	* at once.
	*
	* @{
	*/

	/**
	* Initializes threads, like dbus_threads_init_default().
	* This version previously allowed user-specified threading
	* primitives, but since D-Bus 1.6 it ignores them and behaves
	* exactly like dbus_threads_init_default().
	*
	* @param functions ignored, formerly functions for using threads
	* @returns #TRUE on success, #FALSE if no memory
	*/
	dbus_bool_t
	dbus_threads_init (const DBusThreadFunctions *functions)
	{
	if (thread_init_generation == _dbus_current_generation)
	return TRUE;

	if (!init_locks ())
	return FALSE;

	thread_init_generation = _dbus_current_generation;

	return TRUE;
	}



	/* Default thread implemenation */

	/**
	* Initializes threads. If this function is not called, the D-Bus
	* library will not lock any data structures. If it is called, D-Bus
	* will do locking, at some cost in efficiency. Note that this
	* function must be called BEFORE the second thread is started.
	*
	* It's safe to call dbus_threads_init_default() as many times as you
	* want, but only the first time will have an effect.
	*
	* dbus_shutdown() reverses the effects of this function when it
	* resets all global state in libdbus.
	*
	* @returns #TRUE on success, #FALSE if not enough memory
	*/
	dbus_bool_t
	dbus_threads_init_default (void)
	{
	return _dbus_threads_init_platform_specific ();
	}


	/** @} */

	#ifdef DBUS_BUILD_TESTS

	dbus_bool_t
	_dbus_threads_init_debug (void)
	{
	return _dbus_threads_init_platform_specific();
	}

	#endif /* DBUS_BUILD_TESTS */