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 int thread_init_generation = 0;
31 static DBusList *uninitialized_rmutex_list = NULL;
32 static DBusList *uninitialized_cmutex_list = NULL;
33 static DBusList *uninitialized_condvar_list = NULL;
35 /** This is used for the no-op default mutex pointer, just to be distinct from #NULL */
36 #define _DBUS_DUMMY_MUTEX ((DBusMutex*)0xABCDEF)
37 #define _DBUS_DUMMY_RMUTEX ((DBusRMutex *) _DBUS_DUMMY_MUTEX)
38 #define _DBUS_DUMMY_CMUTEX ((DBusCMutex *) _DBUS_DUMMY_MUTEX)
40 /** This is used for the no-op default mutex pointer, just to be distinct from #NULL */
41 #define _DBUS_DUMMY_CONDVAR ((DBusCondVar*)0xABCDEF2)
44 * @defgroup DBusThreadsInternals Thread functions
45 * @ingroup DBusInternals
46 * @brief _dbus_rmutex_lock(), etc.
48 * Functions and macros related to threads and thread locks.
55 * or creates a no-op mutex if threads are not initialized.
56 * May return #NULL even if threads are initialized, indicating
59 * If possible, the mutex returned by this function is recursive, to
60 * avoid deadlocks. However, that cannot be relied on.
62 * The extra level of indirection given by allocating a pointer
63 * to point to the mutex location allows the threading
64 * module to swap out dummy mutexes for a real mutex so libraries
65 * can initialize threads even after the D-Bus API has been used.
67 * @param location_p the location of the new mutex, can return #NULL on OOM
70 _dbus_rmutex_new_at_location (DBusRMutex **location_p)
72 _dbus_assert (location_p != NULL);
74 if (thread_init_generation == _dbus_current_generation)
76 *location_p = _dbus_platform_rmutex_new ();
80 *location_p = _DBUS_DUMMY_RMUTEX;
82 if (!_dbus_list_append (&uninitialized_rmutex_list, location_p))
89 * or creates a no-op mutex if threads are not initialized.
90 * May return #NULL even if threads are initialized, indicating
93 * The returned mutex is suitable for use with condition variables.
95 * The extra level of indirection given by allocating a pointer
96 * to point to the mutex location allows the threading
97 * module to swap out dummy mutexes for a real mutex so libraries
98 * can initialize threads even after the D-Bus API has been used.
100 * @param location_p the location of the new mutex, can return #NULL on OOM
103 _dbus_cmutex_new_at_location (DBusCMutex **location_p)
105 _dbus_assert (location_p != NULL);
107 if (thread_init_generation == _dbus_current_generation)
109 *location_p = _dbus_platform_cmutex_new ();
113 *location_p = _DBUS_DUMMY_CMUTEX;
115 if (!_dbus_list_append (&uninitialized_cmutex_list, location_p))
121 * Frees a DBusRMutex or removes it from the uninitialized mutex list;
122 * does nothing if passed a #NULL pointer.
125 _dbus_rmutex_free_at_location (DBusRMutex **location_p)
127 if (location_p == NULL)
130 if (thread_init_generation == _dbus_current_generation)
132 if (*location_p != NULL)
133 _dbus_platform_rmutex_free (*location_p);
137 _dbus_assert (*location_p == NULL || *location_p == _DBUS_DUMMY_RMUTEX);
139 _dbus_list_remove (&uninitialized_rmutex_list, location_p);
144 * Frees a DBusCMutex and removes it from the
145 * uninitialized mutex list;
146 * does nothing if passed a #NULL pointer.
149 _dbus_cmutex_free_at_location (DBusCMutex **location_p)
151 if (location_p == NULL)
154 if (thread_init_generation == _dbus_current_generation)
156 if (*location_p != NULL)
157 _dbus_platform_cmutex_free (*location_p);
161 _dbus_assert (*location_p == NULL || *location_p == _DBUS_DUMMY_CMUTEX);
163 _dbus_list_remove (&uninitialized_cmutex_list, location_p);
168 * Locks a mutex. Does nothing if passed a #NULL pointer.
169 * Locks may be recursive if threading implementation initialized
173 _dbus_rmutex_lock (DBusRMutex *mutex)
175 if (mutex && thread_init_generation == _dbus_current_generation)
176 _dbus_platform_rmutex_lock (mutex);
180 * Locks a mutex. Does nothing if passed a #NULL pointer.
181 * Locks may be recursive if threading implementation initialized
185 _dbus_cmutex_lock (DBusCMutex *mutex)
187 if (mutex && thread_init_generation == _dbus_current_generation)
188 _dbus_platform_cmutex_lock (mutex);
192 * Unlocks a mutex. Does nothing if passed a #NULL pointer.
194 * @returns #TRUE on success
197 _dbus_rmutex_unlock (DBusRMutex *mutex)
199 if (mutex && thread_init_generation == _dbus_current_generation)
200 _dbus_platform_rmutex_unlock (mutex);
204 * Unlocks a mutex. Does nothing if passed a #NULL pointer.
206 * @returns #TRUE on success
209 _dbus_cmutex_unlock (DBusCMutex *mutex)
211 if (mutex && thread_init_generation == _dbus_current_generation)
212 _dbus_platform_cmutex_unlock (mutex);
216 * Creates a new condition variable using the function supplied
217 * to dbus_threads_init(), or creates a no-op condition variable
218 * if threads are not initialized. May return #NULL even if
219 * threads are initialized, indicating out-of-memory.
221 * @returns new mutex or #NULL
224 _dbus_condvar_new (void)
226 if (thread_init_generation == _dbus_current_generation)
227 return _dbus_platform_condvar_new ();
229 return _DBUS_DUMMY_CONDVAR;
234 * This does the same thing as _dbus_condvar_new. It however
235 * gives another level of indirection by allocating a pointer
236 * to point to the condvar location. This allows the threading
237 * module to swap out dummy condvars for a real condvar so libraries
238 * can initialize threads even after the D-Bus API has been used.
240 * @returns the location of a new condvar or #NULL on OOM
244 _dbus_condvar_new_at_location (DBusCondVar **location_p)
246 _dbus_assert (location_p != NULL);
248 if (thread_init_generation == _dbus_current_generation)
250 *location_p = _dbus_condvar_new();
254 *location_p = _DBUS_DUMMY_CONDVAR;
256 if (!_dbus_list_append (&uninitialized_condvar_list, location_p))
263 * Frees a conditional variable created with dbus_condvar_new(); does
264 * nothing if passed a #NULL pointer.
267 _dbus_condvar_free (DBusCondVar *cond)
269 if (cond && thread_init_generation == _dbus_current_generation)
270 _dbus_platform_condvar_free (cond);
274 * Frees a conditional variable and removes it from the
275 * uninitialized_condvar_list;
276 * does nothing if passed a #NULL pointer.
279 _dbus_condvar_free_at_location (DBusCondVar **location_p)
281 if (location_p == NULL)
284 if (thread_init_generation == _dbus_current_generation)
286 if (*location_p != NULL)
287 _dbus_platform_condvar_free (*location_p);
291 _dbus_assert (*location_p == NULL || *location_p == _DBUS_DUMMY_CONDVAR);
293 _dbus_list_remove (&uninitialized_condvar_list, location_p);
298 * Atomically unlocks the mutex and waits for the conditions
299 * variable to be signalled. Locks the mutex again before
301 * Does nothing if passed a #NULL pointer.
304 _dbus_condvar_wait (DBusCondVar *cond,
307 if (cond && mutex && thread_init_generation == _dbus_current_generation)
308 _dbus_platform_condvar_wait (cond, mutex);
312 * Atomically unlocks the mutex and waits for the conditions variable
313 * to be signalled, or for a timeout. Locks the mutex again before
314 * returning. Does nothing if passed a #NULL pointer. Return value
315 * is #FALSE if we timed out, #TRUE otherwise.
317 * @param cond the condition variable
318 * @param mutex the mutex
319 * @param timeout_milliseconds the maximum time to wait
320 * @returns #FALSE if the timeout occurred, #TRUE if not
323 _dbus_condvar_wait_timeout (DBusCondVar *cond,
325 int timeout_milliseconds)
327 if (cond && mutex && thread_init_generation == _dbus_current_generation)
328 return _dbus_platform_condvar_wait_timeout (cond, mutex,
329 timeout_milliseconds);
335 * If there are threads waiting on the condition variable, wake
337 * Does nothing if passed a #NULL pointer.
340 _dbus_condvar_wake_one (DBusCondVar *cond)
342 if (cond && thread_init_generation == _dbus_current_generation)
343 _dbus_platform_condvar_wake_one (cond);
346 static DBusRMutex *global_locks[_DBUS_N_GLOBAL_LOCKS] = { NULL };
349 shutdown_global_locks (void *nil)
353 for (i = 0; i < _DBUS_N_GLOBAL_LOCKS; i++)
355 _dbus_assert (global_locks[i] != NULL);
356 _dbus_platform_rmutex_free (global_locks[i]);
357 global_locks[i] = NULL;
362 shutdown_uninitialized_locks (void *data)
364 _dbus_list_clear (&uninitialized_rmutex_list);
365 _dbus_list_clear (&uninitialized_cmutex_list);
366 _dbus_list_clear (&uninitialized_condvar_list);
369 /* init_global_locks() must be called first. */
371 init_uninitialized_locks (void)
376 _dbus_assert (thread_init_generation != _dbus_current_generation);
378 link = uninitialized_rmutex_list;
384 _dbus_assert (*mp == _DBUS_DUMMY_RMUTEX);
386 *mp = _dbus_platform_rmutex_new ();
390 link = _dbus_list_get_next_link (&uninitialized_rmutex_list, link);
393 link = uninitialized_cmutex_list;
399 _dbus_assert (*mp == _DBUS_DUMMY_CMUTEX);
401 *mp = _dbus_platform_cmutex_new ();
405 link = _dbus_list_get_next_link (&uninitialized_cmutex_list, link);
408 link = uninitialized_condvar_list;
413 cp = (DBusCondVar **)link->data;
414 _dbus_assert (*cp == _DBUS_DUMMY_CONDVAR);
416 *cp = _dbus_platform_condvar_new ();
420 link = _dbus_list_get_next_link (&uninitialized_condvar_list, link);
423 _dbus_list_clear (&uninitialized_rmutex_list);
424 _dbus_list_clear (&uninitialized_cmutex_list);
425 _dbus_list_clear (&uninitialized_condvar_list);
427 /* This assumes that init_global_locks() has already been called. */
428 _dbus_platform_rmutex_lock (global_locks[_DBUS_LOCK_shutdown_funcs]);
429 ok = _dbus_register_shutdown_func_unlocked (shutdown_uninitialized_locks, NULL);
430 _dbus_platform_rmutex_unlock (global_locks[_DBUS_LOCK_shutdown_funcs]);
438 link = uninitialized_condvar_list;
445 if (*cp != _DBUS_DUMMY_CONDVAR && *cp != NULL)
446 _dbus_platform_condvar_free (*cp);
448 *cp = _DBUS_DUMMY_CONDVAR;
450 link = _dbus_list_get_next_link (&uninitialized_condvar_list, link);
454 link = uninitialized_rmutex_list;
461 if (*mp != _DBUS_DUMMY_RMUTEX && *mp != NULL)
462 _dbus_platform_rmutex_free (*mp);
464 *mp = _DBUS_DUMMY_RMUTEX;
466 link = _dbus_list_get_next_link (&uninitialized_rmutex_list, link);
469 link = uninitialized_cmutex_list;
476 if (*mp != _DBUS_DUMMY_CMUTEX && *mp != NULL)
477 _dbus_platform_cmutex_free (*mp);
479 *mp = _DBUS_DUMMY_CMUTEX;
481 link = _dbus_list_get_next_link (&uninitialized_cmutex_list, link);
488 init_global_locks (void)
493 for (i = 0; i < _DBUS_N_GLOBAL_LOCKS; i++)
495 _dbus_assert (global_locks[i] == NULL);
497 global_locks[i] = _dbus_platform_rmutex_new ();
499 if (global_locks[i] == NULL)
503 _dbus_platform_rmutex_lock (global_locks[_DBUS_LOCK_shutdown_funcs]);
504 ok = _dbus_register_shutdown_func_unlocked (shutdown_global_locks, NULL);
505 _dbus_platform_rmutex_unlock (global_locks[_DBUS_LOCK_shutdown_funcs]);
513 for (i = i - 1; i >= 0; i--)
515 _dbus_platform_rmutex_free (global_locks[i]);
516 global_locks[i] = NULL;
523 _dbus_lock (DBusGlobalLock lock)
525 _dbus_assert (lock >= 0);
526 _dbus_assert (lock < _DBUS_N_GLOBAL_LOCKS);
528 if (thread_init_generation != _dbus_current_generation &&
529 !dbus_threads_init_default ())
532 _dbus_platform_rmutex_lock (global_locks[lock]);
537 _dbus_unlock (DBusGlobalLock lock)
539 _dbus_assert (lock >= 0);
540 _dbus_assert (lock < _DBUS_N_GLOBAL_LOCKS);
542 _dbus_platform_rmutex_unlock (global_locks[lock]);
545 /** @} */ /* end of internals */
548 * @defgroup DBusThreads Thread functions
550 * @brief dbus_threads_init() and dbus_threads_init_default()
552 * Functions and macros related to threads and thread locks.
554 * If threads are initialized, the D-Bus library has locks on all
555 * global data structures. In addition, each #DBusConnection has a
556 * lock, so only one thread at a time can touch the connection. (See
557 * @ref DBusConnection for more on connection locking.)
559 * Most other objects, however, do not have locks - they can only be
560 * used from a single thread at a time, unless you lock them yourself.
561 * For example, a #DBusMessage can't be modified from two threads
568 * Initializes threads, like dbus_threads_init_default().
569 * This version previously allowed user-specified threading
570 * primitives, but since D-Bus 1.6 it ignores them and behaves
571 * exactly like dbus_threads_init_default().
573 * @param functions ignored, formerly functions for using threads
574 * @returns #TRUE on success, #FALSE if no memory
577 dbus_threads_init (const DBusThreadFunctions *functions)
579 _dbus_threads_lock_platform_specific ();
581 if (thread_init_generation == _dbus_current_generation)
583 _dbus_threads_unlock_platform_specific ();
587 if (!_dbus_threads_init_platform_specific() ||
588 /* init_global_locks() must be called before init_uninitialized_locks. */
589 !init_global_locks () ||
590 !init_uninitialized_locks ())
592 _dbus_threads_unlock_platform_specific ();
596 thread_init_generation = _dbus_current_generation;
598 _dbus_threads_unlock_platform_specific ();
604 /* Default thread implemenation */
607 * Initializes threads. If this function is not called, the D-Bus
608 * library will not lock any data structures. If it is called, D-Bus
609 * will do locking, at some cost in efficiency.
611 * Since D-Bus 1.7 it is safe to call this function from any thread,
612 * any number of times (but it must be called before any other
613 * libdbus API is used).
615 * In D-Bus 1.6 or older, this function must be called in the main thread
616 * before any other thread starts. As a result, it is not sufficient to
617 * call this function in a library or plugin, unless the library or plugin
618 * imposes a similar requirement on its callers.
620 * dbus_shutdown() reverses the effects of this function when it
621 * resets all global state in libdbus.
623 * @returns #TRUE on success, #FALSE if not enough memory
626 dbus_threads_init_default (void)
628 return dbus_threads_init (NULL);
634 #ifdef DBUS_BUILD_TESTS
637 _dbus_threads_init_debug (void)
639 return dbus_threads_init (NULL);
642 #endif /* DBUS_BUILD_TESTS */