1 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
2 /* dbus-threads.h D-Bus threads handling
4 * Copyright (C) 2002, 2003, 2006 Red Hat Inc.
6 * Licensed under the Academic Free License version 2.1
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 #include "dbus-threads.h"
25 #include "dbus-internals.h"
26 #include "dbus-threads-internal.h"
27 #include "dbus-list.h"
29 static DBusThreadFunctions thread_functions =
32 NULL, NULL, NULL, NULL, NULL,
33 NULL, NULL, NULL, NULL, NULL,
34 NULL, NULL, NULL, NULL,
36 NULL, NULL, NULL, NULL
39 static int thread_init_generation = 0;
41 static DBusList *uninitialized_mutex_list = NULL;
42 static DBusList *uninitialized_condvar_list = NULL;
44 /** This is used for the no-op default mutex pointer, just to be distinct from #NULL */
45 #define _DBUS_DUMMY_MUTEX ((DBusMutex*)0xABCDEF)
47 /** This is used for the no-op default mutex pointer, just to be distinct from #NULL */
48 #define _DBUS_DUMMY_CONDVAR ((DBusCondVar*)0xABCDEF2)
50 static void _dbus_mutex_free (DBusMutex *mutex);
53 * @defgroup DBusThreadsInternals Thread functions
54 * @ingroup DBusInternals
55 * @brief _dbus_mutex_lock(), etc.
57 * Functions and macros related to threads and thread locks.
63 _dbus_mutex_new (void)
65 if (thread_functions.recursive_mutex_new)
66 return (* thread_functions.recursive_mutex_new) ();
67 else if (thread_functions.mutex_new)
68 return (* thread_functions.mutex_new) ();
70 return _DBUS_DUMMY_MUTEX;
74 * Creates a new mutex using the function supplied to dbus_threads_init(),
75 * or creates a no-op mutex if threads are not initialized.
76 * May return #NULL even if threads are initialized, indicating
79 * The extra level of indirection given by allocating a pointer
80 * to point to the mutex location allows the threading
81 * module to swap out dummy mutexes for real a real mutex so libraries
82 * can initialize threads even after the D-Bus API has been used.
84 * @param location_p the location of the new mutex, can return #NULL on OOM
87 _dbus_mutex_new_at_location (DBusMutex **location_p)
89 _dbus_assert (location_p != NULL);
91 *location_p = _dbus_mutex_new();
93 if (thread_init_generation != _dbus_current_generation && *location_p)
95 if (!_dbus_list_append (&uninitialized_mutex_list, location_p))
97 _dbus_mutex_free (*location_p);
104 _dbus_mutex_free (DBusMutex *mutex)
108 if (mutex && thread_functions.recursive_mutex_free)
109 (* thread_functions.recursive_mutex_free) (mutex);
110 else if (mutex && thread_functions.mutex_free)
111 (* thread_functions.mutex_free) (mutex);
116 * Frees a mutex and removes it from the
117 * uninitialized_mutex_list;
118 * does nothing if passed a #NULL pointer.
121 _dbus_mutex_free_at_location (DBusMutex **location_p)
125 if (thread_init_generation != _dbus_current_generation)
126 _dbus_list_remove (&uninitialized_mutex_list, location_p);
128 _dbus_mutex_free (*location_p);
133 * Locks a mutex. Does nothing if passed a #NULL pointer.
134 * Locks may be recursive if threading implementation initialized
138 _dbus_mutex_lock (DBusMutex *mutex)
142 if (thread_functions.recursive_mutex_lock)
143 (* thread_functions.recursive_mutex_lock) (mutex);
144 else if (thread_functions.mutex_lock)
145 (* thread_functions.mutex_lock) (mutex);
150 * Unlocks a mutex. Does nothing if passed a #NULL pointer.
152 * @returns #TRUE on success
155 _dbus_mutex_unlock (DBusMutex *mutex)
159 if (thread_functions.recursive_mutex_unlock)
160 (* thread_functions.recursive_mutex_unlock) (mutex);
161 else if (thread_functions.mutex_unlock)
162 (* thread_functions.mutex_unlock) (mutex);
167 * Creates a new condition variable using the function supplied
168 * to dbus_threads_init(), or creates a no-op condition variable
169 * if threads are not initialized. May return #NULL even if
170 * threads are initialized, indicating out-of-memory.
172 * @returns new mutex or #NULL
175 _dbus_condvar_new (void)
177 if (thread_functions.condvar_new)
178 return (* thread_functions.condvar_new) ();
180 return _DBUS_DUMMY_CONDVAR;
185 * This does the same thing as _dbus_condvar_new. It however
186 * gives another level of indirection by allocating a pointer
187 * to point to the condvar location. This allows the threading
188 * module to swap out dummy condvars for real a real condvar so libraries
189 * can initialize threads even after the D-Bus API has been used.
191 * @returns the location of a new condvar or #NULL on OOM
195 _dbus_condvar_new_at_location (DBusCondVar **location_p)
197 *location_p = _dbus_condvar_new();
199 if (thread_init_generation != _dbus_current_generation && *location_p)
201 if (!_dbus_list_append (&uninitialized_condvar_list, location_p))
203 _dbus_condvar_free (*location_p);
211 * Frees a conditional variable created with dbus_condvar_new(); does
212 * nothing if passed a #NULL pointer.
215 _dbus_condvar_free (DBusCondVar *cond)
217 if (cond && thread_functions.condvar_free)
218 (* thread_functions.condvar_free) (cond);
222 * Frees a conditional variable and removes it from the
223 * uninitialized_condvar_list;
224 * does nothing if passed a #NULL pointer.
227 _dbus_condvar_free_at_location (DBusCondVar **location_p)
231 if (thread_init_generation != _dbus_current_generation)
232 _dbus_list_remove (&uninitialized_condvar_list, location_p);
234 _dbus_condvar_free (*location_p);
239 * Atomically unlocks the mutex and waits for the conditions
240 * variable to be signalled. Locks the mutex again before
242 * Does nothing if passed a #NULL pointer.
245 _dbus_condvar_wait (DBusCondVar *cond,
248 if (cond && mutex && thread_functions.condvar_wait)
249 (* thread_functions.condvar_wait) (cond, mutex);
253 * Atomically unlocks the mutex and waits for the conditions variable
254 * to be signalled, or for a timeout. Locks the mutex again before
255 * returning. Does nothing if passed a #NULL pointer. Return value
256 * is #FALSE if we timed out, #TRUE otherwise.
258 * @param cond the condition variable
259 * @param mutex the mutex
260 * @param timeout_milliseconds the maximum time to wait
261 * @returns #FALSE if the timeout occurred, #TRUE if not
264 _dbus_condvar_wait_timeout (DBusCondVar *cond,
266 int timeout_milliseconds)
268 if (cond && mutex && thread_functions.condvar_wait)
269 return (* thread_functions.condvar_wait_timeout) (cond, mutex, timeout_milliseconds);
275 * If there are threads waiting on the condition variable, wake
277 * Does nothing if passed a #NULL pointer.
280 _dbus_condvar_wake_one (DBusCondVar *cond)
282 if (cond && thread_functions.condvar_wake_one)
283 (* thread_functions.condvar_wake_one) (cond);
287 * If there are threads waiting on the condition variable, wake
289 * Does nothing if passed a #NULL pointer.
292 _dbus_condvar_wake_all (DBusCondVar *cond)
294 if (cond && thread_functions.condvar_wake_all)
295 (* thread_functions.condvar_wake_all) (cond);
299 shutdown_global_locks (void *data)
301 DBusMutex ***locks = data;
305 while (i < _DBUS_N_GLOBAL_LOCKS)
307 _dbus_mutex_free (*(locks[i]));
316 shutdown_uninitialized_locks (void *data)
318 _dbus_list_clear (&uninitialized_mutex_list);
319 _dbus_list_clear (&uninitialized_condvar_list);
323 init_uninitialized_locks (void)
327 _dbus_assert (thread_init_generation != _dbus_current_generation);
329 link = uninitialized_mutex_list;
334 mp = (DBusMutex **)link->data;
335 _dbus_assert (*mp == _DBUS_DUMMY_MUTEX);
337 *mp = _dbus_mutex_new ();
341 link = _dbus_list_get_next_link (&uninitialized_mutex_list, link);
344 link = uninitialized_condvar_list;
349 cp = (DBusCondVar **)link->data;
350 _dbus_assert (*cp == _DBUS_DUMMY_CONDVAR);
352 *cp = _dbus_condvar_new ();
356 link = _dbus_list_get_next_link (&uninitialized_condvar_list, link);
359 _dbus_list_clear (&uninitialized_mutex_list);
360 _dbus_list_clear (&uninitialized_condvar_list);
362 if (!_dbus_register_shutdown_func (shutdown_uninitialized_locks,
369 link = uninitialized_condvar_list;
374 cp = (DBusCondVar **)link->data;
376 if (*cp != _DBUS_DUMMY_CONDVAR)
377 _dbus_condvar_free (*cp);
381 *cp = _DBUS_DUMMY_CONDVAR;
383 link = _dbus_list_get_next_link (&uninitialized_condvar_list, link);
387 link = uninitialized_mutex_list;
392 mp = (DBusMutex **)link->data;
394 if (*mp != _DBUS_DUMMY_MUTEX)
395 _dbus_mutex_free (*mp);
399 *mp = _DBUS_DUMMY_MUTEX;
401 link = _dbus_list_get_next_link (&uninitialized_mutex_list, link);
411 DBusMutex ***dynamic_global_locks;
413 DBusMutex **global_locks[] = {
414 #define LOCK_ADDR(name) (& _dbus_lock_##name)
416 LOCK_ADDR (sid_atom_cache),
418 LOCK_ADDR (connection_slots),
419 LOCK_ADDR (pending_call_slots),
420 LOCK_ADDR (server_slots),
421 LOCK_ADDR (message_slots),
426 LOCK_ADDR (bus_datas),
427 LOCK_ADDR (shutdown_funcs),
428 LOCK_ADDR (system_users),
429 LOCK_ADDR (message_cache),
430 LOCK_ADDR (shared_connections),
431 LOCK_ADDR (machine_uuid)
435 _dbus_assert (_DBUS_N_ELEMENTS (global_locks) ==
436 _DBUS_N_GLOBAL_LOCKS);
440 dynamic_global_locks = dbus_new (DBusMutex**, _DBUS_N_GLOBAL_LOCKS);
441 if (dynamic_global_locks == NULL)
444 while (i < _DBUS_N_ELEMENTS (global_locks))
446 *global_locks[i] = _dbus_mutex_new ();
448 if (*global_locks[i] == NULL)
451 dynamic_global_locks[i] = global_locks[i];
456 if (!_dbus_register_shutdown_func (shutdown_global_locks,
457 dynamic_global_locks))
460 if (!init_uninitialized_locks ())
466 dbus_free (dynamic_global_locks);
468 for (i = i - 1; i >= 0; i--)
470 _dbus_mutex_free (*global_locks[i]);
471 *global_locks[i] = NULL;
476 /** @} */ /* end of internals */
479 * @defgroup DBusThreads Thread functions
481 * @brief dbus_threads_init() and dbus_threads_init_default()
483 * Functions and macros related to threads and thread locks.
485 * If threads are initialized, the D-Bus library has locks on all
486 * global data structures. In addition, each #DBusConnection has a
487 * lock, so only one thread at a time can touch the connection. (See
488 * @ref DBusConnection for more on connection locking.)
490 * Most other objects, however, do not have locks - they can only be
491 * used from a single thread at a time, unless you lock them yourself.
492 * For example, a #DBusMessage can't be modified from two threads
500 * Initializes threads. If this function is not called, the D-Bus
501 * library will not lock any data structures. If it is called, D-Bus
502 * will do locking, at some cost in efficiency. Note that this
503 * function must be called BEFORE the second thread is started.
505 * Almost always, you should use dbus_threads_init_default() instead.
506 * The raw dbus_threads_init() is only useful if you require a
507 * particular thread implementation for some reason.
509 * A possible reason to use dbus_threads_init() rather than
510 * dbus_threads_init_default() is to insert debugging checks or print
513 * dbus_threads_init() may be called more than once. The first one
514 * wins and subsequent calls are ignored. (Unless you use
515 * dbus_shutdown() to reset libdbus, which will let you re-init
518 * Either recursive or nonrecursive mutex functions must be specified,
519 * but not both. New code should provide only the recursive functions
520 * - specifying the nonrecursive ones is deprecated.
522 * Because this function effectively sets global state, all code
523 * running in a given application must agree on the thread
524 * implementation. Most code won't care which thread implementation is
525 * used, so there's no problem. However, usually libraries should not
526 * call dbus_threads_init() or dbus_threads_init_default(), instead
527 * leaving this policy choice to applications.
529 * The exception is for application frameworks (GLib, Qt, etc.) and
530 * D-Bus bindings based on application frameworks. These frameworks
531 * define a cross-platform thread abstraction and can assume
532 * applications using the framework are OK with using that thread
535 * However, even these app frameworks may find it easier to simply call
536 * dbus_threads_init_default(), and there's no reason they shouldn't.
538 * @param functions functions for using threads
539 * @returns #TRUE on success, #FALSE if no memory
542 dbus_threads_init (const DBusThreadFunctions *functions)
544 dbus_bool_t mutex_set;
545 dbus_bool_t recursive_mutex_set;
547 _dbus_assert (functions != NULL);
549 /* these base functions are required. Future additions to
550 * DBusThreadFunctions may be optional.
552 _dbus_assert (functions->mask & DBUS_THREAD_FUNCTIONS_CONDVAR_NEW_MASK);
553 _dbus_assert (functions->mask & DBUS_THREAD_FUNCTIONS_CONDVAR_FREE_MASK);
554 _dbus_assert (functions->mask & DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_MASK);
555 _dbus_assert (functions->mask & DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_TIMEOUT_MASK);
556 _dbus_assert (functions->mask & DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ONE_MASK);
557 _dbus_assert (functions->mask & DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ALL_MASK);
558 _dbus_assert (functions->condvar_new != NULL);
559 _dbus_assert (functions->condvar_free != NULL);
560 _dbus_assert (functions->condvar_wait != NULL);
561 _dbus_assert (functions->condvar_wait_timeout != NULL);
562 _dbus_assert (functions->condvar_wake_one != NULL);
563 _dbus_assert (functions->condvar_wake_all != NULL);
565 /* Either the mutex function set or recursive mutex set needs
566 * to be available but not both
568 mutex_set = (functions->mask & DBUS_THREAD_FUNCTIONS_MUTEX_NEW_MASK) &&
569 (functions->mask & DBUS_THREAD_FUNCTIONS_MUTEX_FREE_MASK) &&
570 (functions->mask & DBUS_THREAD_FUNCTIONS_MUTEX_LOCK_MASK) &&
571 (functions->mask & DBUS_THREAD_FUNCTIONS_MUTEX_UNLOCK_MASK) &&
572 functions->mutex_new &&
573 functions->mutex_free &&
574 functions->mutex_lock &&
575 functions->mutex_unlock;
577 recursive_mutex_set =
578 (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_NEW_MASK) &&
579 (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_FREE_MASK) &&
580 (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_LOCK_MASK) &&
581 (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_UNLOCK_MASK) &&
582 functions->recursive_mutex_new &&
583 functions->recursive_mutex_free &&
584 functions->recursive_mutex_lock &&
585 functions->recursive_mutex_unlock;
587 if (!(mutex_set || recursive_mutex_set))
588 _dbus_assert_not_reached ("Either the nonrecusrive or recursive mutex "
589 "functions sets should be passed into "
590 "dbus_threads_init. Neither sets were passed.");
592 if (mutex_set && recursive_mutex_set)
593 _dbus_assert_not_reached ("Either the nonrecusrive or recursive mutex "
594 "functions sets should be passed into "
595 "dbus_threads_init. Both sets were passed. "
596 "You most likely just want to set the recursive "
597 "mutex functions to avoid deadlocks in D-Bus.");
599 /* Check that all bits in the mask actually are valid mask bits.
600 * ensures people won't write code that breaks when we add
603 _dbus_assert ((functions->mask & ~DBUS_THREAD_FUNCTIONS_ALL_MASK) == 0);
605 if (thread_init_generation != _dbus_current_generation)
606 thread_functions.mask = 0; /* allow re-init in new generation */
608 /* Silently allow multiple init
609 * First init wins and D-Bus will always use its threading system
611 if (thread_functions.mask != 0)
614 thread_functions.mutex_new = functions->mutex_new;
615 thread_functions.mutex_free = functions->mutex_free;
616 thread_functions.mutex_lock = functions->mutex_lock;
617 thread_functions.mutex_unlock = functions->mutex_unlock;
619 thread_functions.condvar_new = functions->condvar_new;
620 thread_functions.condvar_free = functions->condvar_free;
621 thread_functions.condvar_wait = functions->condvar_wait;
622 thread_functions.condvar_wait_timeout = functions->condvar_wait_timeout;
623 thread_functions.condvar_wake_one = functions->condvar_wake_one;
624 thread_functions.condvar_wake_all = functions->condvar_wake_all;
626 if (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_NEW_MASK)
627 thread_functions.recursive_mutex_new = functions->recursive_mutex_new;
629 if (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_FREE_MASK)
630 thread_functions.recursive_mutex_free = functions->recursive_mutex_free;
632 if (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_LOCK_MASK)
633 thread_functions.recursive_mutex_lock = functions->recursive_mutex_lock;
635 if (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_UNLOCK_MASK)
636 thread_functions.recursive_mutex_unlock = functions->recursive_mutex_unlock;
638 thread_functions.mask = functions->mask;
643 thread_init_generation = _dbus_current_generation;
650 /* Default thread implemenation */
654 * Calls dbus_threads_init() with a default set of
655 * #DBusThreadFunctions appropriate for the platform.
657 * Most applications should use this rather than dbus_threads_init().
659 * It's safe to call dbus_threads_init_default() as many times as you
660 * want, but only the first time will have an effect.
662 * dbus_shutdown() reverses the effects of this function when it
663 * resets all global state in libdbus.
665 * @returns #TRUE on success, #FALSE if not enough memory
668 dbus_threads_init_default (void)
670 return _dbus_threads_init_platform_specific ();
676 #ifdef DBUS_BUILD_TESTS
677 /** Fake mutex used for debugging */
678 typedef struct DBusFakeMutex DBusFakeMutex;
679 /** Fake mutex used for debugging */
682 dbus_bool_t locked; /**< Mutex is "locked" */
685 static DBusMutex * dbus_fake_mutex_new (void);
686 static void dbus_fake_mutex_free (DBusMutex *mutex);
687 static dbus_bool_t dbus_fake_mutex_lock (DBusMutex *mutex);
688 static dbus_bool_t dbus_fake_mutex_unlock (DBusMutex *mutex);
689 static DBusCondVar* dbus_fake_condvar_new (void);
690 static void dbus_fake_condvar_free (DBusCondVar *cond);
691 static void dbus_fake_condvar_wait (DBusCondVar *cond,
693 static dbus_bool_t dbus_fake_condvar_wait_timeout (DBusCondVar *cond,
696 static void dbus_fake_condvar_wake_one (DBusCondVar *cond);
697 static void dbus_fake_condvar_wake_all (DBusCondVar *cond);
700 static const DBusThreadFunctions fake_functions =
702 DBUS_THREAD_FUNCTIONS_MUTEX_NEW_MASK |
703 DBUS_THREAD_FUNCTIONS_MUTEX_FREE_MASK |
704 DBUS_THREAD_FUNCTIONS_MUTEX_LOCK_MASK |
705 DBUS_THREAD_FUNCTIONS_MUTEX_UNLOCK_MASK |
706 DBUS_THREAD_FUNCTIONS_CONDVAR_NEW_MASK |
707 DBUS_THREAD_FUNCTIONS_CONDVAR_FREE_MASK |
708 DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_MASK |
709 DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_TIMEOUT_MASK |
710 DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ONE_MASK|
711 DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ALL_MASK,
713 dbus_fake_mutex_free,
714 dbus_fake_mutex_lock,
715 dbus_fake_mutex_unlock,
716 dbus_fake_condvar_new,
717 dbus_fake_condvar_free,
718 dbus_fake_condvar_wait,
719 dbus_fake_condvar_wait_timeout,
720 dbus_fake_condvar_wake_one,
721 dbus_fake_condvar_wake_all
725 dbus_fake_mutex_new (void)
727 DBusFakeMutex *mutex;
729 mutex = dbus_new0 (DBusFakeMutex, 1);
731 return (DBusMutex *)mutex;
735 dbus_fake_mutex_free (DBusMutex *mutex)
737 DBusFakeMutex *fake = (DBusFakeMutex*) mutex;
739 _dbus_assert (!fake->locked);
745 dbus_fake_mutex_lock (DBusMutex *mutex)
747 DBusFakeMutex *fake = (DBusFakeMutex*) mutex;
749 _dbus_assert (!fake->locked);
757 dbus_fake_mutex_unlock (DBusMutex *mutex)
759 DBusFakeMutex *fake = (DBusFakeMutex*) mutex;
761 _dbus_assert (fake->locked);
763 fake->locked = FALSE;
769 dbus_fake_condvar_new (void)
771 return (DBusCondVar*) _dbus_strdup ("FakeCondvar");
775 dbus_fake_condvar_free (DBusCondVar *cond)
781 dbus_fake_condvar_wait (DBusCondVar *cond,
788 dbus_fake_condvar_wait_timeout (DBusCondVar *cond,
796 dbus_fake_condvar_wake_one (DBusCondVar *cond)
802 dbus_fake_condvar_wake_all (DBusCondVar *cond)
808 _dbus_threads_init_debug (void)
811 return _dbus_threads_init_platform_specific();
813 return dbus_threads_init (&fake_functions);
817 #endif /* DBUS_BUILD_TESTS */