1 /* GLIB - Library of useful routines for C programming
2 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
4 * gthread.c: MT safety related functions
5 * Copyright 1998 Sebastian Wilhelmi; University of Karlsruhe
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2 of the License, or (at your option) any later version.
13 * This library 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 GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the
20 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
21 * Boston, MA 02111-1307, USA.
24 /* Prelude {{{1 ----------------------------------------------------------- */
27 * Modified by the GLib Team and others 1997-2000. See the AUTHORS
28 * file for a list of people on the GLib Team. See the ChangeLog
29 * files for a list of changes. These files are distributed with
30 * GLib at ftp://ftp.gtk.org/pub/gtk/.
37 /* implement gthread.h's inline functions */
38 #define G_IMPLEMENT_INLINES 1
39 #define __G_THREAD_C__
44 #include "gthreadprivate.h"
57 #endif /* G_OS_WIN32 */
64 #include "gtestutils.h"
70 * @short_description: thread abstraction; including threads, different
71 * mutexes, conditions and thread private data
72 * @see_also: #GThreadPool, #GAsyncQueue
74 * Threads act almost like processes, but unlike processes all threads
75 * of one process share the same memory. This is good, as it provides
76 * easy communication between the involved threads via this shared
77 * memory, and it is bad, because strange things (so called
78 * "Heisenbugs") might happen if the program is not carefully designed.
79 * In particular, due to the concurrent nature of threads, no
80 * assumptions on the order of execution of code running in different
81 * threads can be made, unless order is explicitly forced by the
82 * programmer through synchronization primitives.
84 * The aim of the thread related functions in GLib is to provide a
85 * portable means for writing multi-threaded software. There are
86 * primitives for mutexes to protect the access to portions of memory
87 * (#GMutex, #GStaticMutex, #G_LOCK_DEFINE, #GStaticRecMutex and
88 * #GStaticRWLock). There is a facility to use individual bits for
89 * locks (g_bit_lock()). There are primitives for condition variables to
90 * allow synchronization of threads (#GCond). There are primitives for
91 * thread-private data - data that every thread has a private instance
92 * of (#GPrivate, #GStaticPrivate). There are facilities for one-time
93 * initialization (#GOnce, g_once_init_enter()). Last but definitely
94 * not least there are primitives to portably create and manage
97 * The threading system is initialized with g_thread_init(), which
98 * takes an optional custom thread implementation or %NULL for the
99 * default implementation. If you want to call g_thread_init() with a
100 * non-%NULL argument this must be done before executing any other GLib
101 * functions (except g_mem_set_vtable()). This is a requirement even if
102 * no threads are in fact ever created by the process.
104 * Calling g_thread_init() with a %NULL argument is somewhat more
105 * relaxed. You may call any other glib functions in the main thread
106 * before g_thread_init() as long as g_thread_init() is not called from
107 * a glib callback, or with any locks held. However, many libraries
108 * above glib does not support late initialization of threads, so doing
109 * this should be avoided if possible.
111 * Please note that since version 2.24 the GObject initialization
112 * function g_type_init() initializes threads (with a %NULL argument),
113 * so most applications, including those using Gtk+ will run with
114 * threads enabled. If you want a special thread implementation, make
115 * sure you call g_thread_init() before g_type_init() is called.
117 * After calling g_thread_init(), GLib is completely thread safe (all
118 * global data is automatically locked), but individual data structure
119 * instances are not automatically locked for performance reasons. So,
120 * for example you must coordinate accesses to the same #GHashTable
121 * from multiple threads. The two notable exceptions from this rule
122 * are #GMainLoop and #GAsyncQueue, which <emphasis>are</emphasis>
123 * threadsafe and need no further application-level locking to be
124 * accessed from multiple threads.
126 * To help debugging problems in multithreaded applications, GLib
127 * supports error-checking mutexes that will give you helpful error
128 * messages on common problems. To use error-checking mutexes, define
129 * the symbol #G_ERRORCHECK_MUTEXES when compiling the application.
133 * G_THREADS_IMPL_POSIX:
135 * This macro is defined if POSIX style threads are used.
141 * This macro is defined, for backward compatibility, to indicate that
142 * GLib has been compiled with thread support. As of glib 2.28, it is
147 * G_THREADS_IMPL_NONE:
149 * This macro is defined if no thread implementation is used. You can,
150 * however, provide one to g_thread_init() to make GLib multi-thread
154 /* G_LOCK Documentation {{{1 ---------------------------------------------- */
156 /* IMPLEMENTATION NOTE:
158 * G_LOCK_DEFINE and friends are convenience macros defined in
159 * gthread.h. Their documentation lives here.
164 * @name: the name of the lock.
166 * The %G_LOCK_* macros provide a convenient interface to #GStaticMutex
167 * with the advantage that they will expand to nothing in programs
168 * compiled against a thread-disabled GLib, saving code and memory
169 * there. #G_LOCK_DEFINE defines a lock. It can appear anywhere
170 * variable definitions may appear in programs, i.e. in the first block
171 * of a function or outside of functions. The @name parameter will be
172 * mangled to get the name of the #GStaticMutex. This means that you
173 * can use names of existing variables as the parameter - e.g. the name
174 * of the variable you intent to protect with the lock. Look at our
175 * <function>give_me_next_number()</function> example using the
179 * <title>Using the %G_LOCK_* convenience macros</title>
181 * G_LOCK_DEFINE (current_number);
184 * give_me_next_number (void)
186 * static int current_number = 0;
189 * G_LOCK (current_number);
190 * ret_val = current_number = calc_next_number (current_number);
191 * G_UNLOCK (current_number);
200 * G_LOCK_DEFINE_STATIC:
201 * @name: the name of the lock.
203 * This works like #G_LOCK_DEFINE, but it creates a static object.
208 * @name: the name of the lock.
210 * This declares a lock, that is defined with #G_LOCK_DEFINE in another
216 * @name: the name of the lock.
218 * Works like g_mutex_lock(), but for a lock defined with
224 * @name: the name of the lock.
225 * @Returns: %TRUE, if the lock could be locked.
227 * Works like g_mutex_trylock(), but for a lock defined with
233 * @name: the name of the lock.
235 * Works like g_mutex_unlock(), but for a lock defined with
239 /* GThreadError {{{1 ------------------------------------------------------- */
242 * @G_THREAD_ERROR_AGAIN: a thread couldn't be created due to resource
243 * shortage. Try again later.
245 * Possible errors of thread related functions.
251 * The error domain of the GLib thread subsystem.
254 g_thread_error_quark (void)
256 return g_quark_from_static_string ("g_thread_error");
259 /* Miscellaneous Structures {{{1 ------------------------------------------ */
260 typedef struct _GRealThread GRealThread;
264 /* Bit 0 protects private_data. To avoid deadlocks, do not block while
265 * holding this (particularly on the g_thread lock). */
266 volatile gint private_data_lock;
267 GArray *private_data;
270 GSystemThread system_thread;
273 #define LOCK_PRIVATE_DATA(self) g_bit_lock (&(self)->private_data_lock, 0)
274 #define UNLOCK_PRIVATE_DATA(self) g_bit_unlock (&(self)->private_data_lock, 0)
276 typedef struct _GStaticPrivateNode GStaticPrivateNode;
277 struct _GStaticPrivateNode
280 GDestroyNotify destroy;
283 static void g_thread_cleanup (gpointer data);
284 static void g_thread_fail (void);
285 static guint64 gettime (void);
287 guint64 (*g_thread_gettime) (void) = gettime;
289 /* Global Variables {{{1 -------------------------------------------------- */
291 static GSystemThread zero_thread; /* This is initialized to all zero */
292 gboolean g_thread_use_default_impl = TRUE;
295 * g_thread_supported:
296 * @Returns: %TRUE, if the thread system is initialized.
298 * This function returns %TRUE if the thread system is initialized, and
299 * %FALSE if it is not.
301 * <note><para>This function is actually a macro. Apart from taking the
302 * address of it you can however use it as if it was a
303 * function.</para></note>
306 /* IMPLEMENTATION NOTE:
308 * g_thread_supported() is just returns g_threads_got_initialized
310 gboolean g_threads_got_initialized = FALSE;
313 /* Thread Implementation Virtual Function Table {{{1 ---------------------- */
314 /* Virtual Function Table Documentation {{{2 ------------------------------ */
317 * @mutex_new: virtual function pointer for g_mutex_new()
318 * @mutex_lock: virtual function pointer for g_mutex_lock()
319 * @mutex_trylock: virtual function pointer for g_mutex_trylock()
320 * @mutex_unlock: virtual function pointer for g_mutex_unlock()
321 * @mutex_free: virtual function pointer for g_mutex_free()
322 * @cond_new: virtual function pointer for g_cond_new()
323 * @cond_signal: virtual function pointer for g_cond_signal()
324 * @cond_broadcast: virtual function pointer for g_cond_broadcast()
325 * @cond_wait: virtual function pointer for g_cond_wait()
326 * @cond_timed_wait: virtual function pointer for g_cond_timed_wait()
327 * @cond_free: virtual function pointer for g_cond_free()
328 * @private_new: virtual function pointer for g_private_new()
329 * @private_get: virtual function pointer for g_private_get()
330 * @private_set: virtual function pointer for g_private_set()
331 * @thread_create: virtual function pointer for g_thread_create()
332 * @thread_yield: virtual function pointer for g_thread_yield()
333 * @thread_join: virtual function pointer for g_thread_join()
334 * @thread_exit: virtual function pointer for g_thread_exit()
335 * @thread_set_priority: virtual function pointer for
336 * g_thread_set_priority()
337 * @thread_self: virtual function pointer for g_thread_self()
338 * @thread_equal: used internally by recursive mutex locks and by some
341 * This function table is used by g_thread_init() to initialize the
342 * thread system. The functions in the table are directly used by their
343 * g_* prepended counterparts (described in this document). For
344 * example, if you call g_mutex_new() then mutex_new() from the table
345 * provided to g_thread_init() will be called.
347 * <note><para>Do not use this struct unless you know what you are
348 * doing.</para></note>
351 /* IMPLEMENTATION NOTE:
353 * g_thread_functions_for_glib_use is a global symbol that gets used by
354 * most of the "primitive" threading calls. g_mutex_lock(), for
355 * example, is just a macro that calls the appropriate virtual function
358 * For that reason, all of those macros are documented here.
360 static GThreadFunctions g_thread_functions_for_glib_use_old = {
361 /* GMutex Virtual Functions {{{2 ------------------------------------------ */
366 * The #GMutex struct is an opaque data structure to represent a mutex
367 * (mutual exclusion). It can be used to protect data against shared
368 * access. Take for example the following function:
371 * <title>A function which will not work in a threaded environment</title>
374 * give_me_next_number (void)
376 * static int current_number = 0;
378 * /<!-- -->* now do a very complicated calculation to calculate the new
379 * * number, this might for example be a random number generator
381 * current_number = calc_next_number (current_number);
383 * return current_number;
388 * It is easy to see that this won't work in a multi-threaded
389 * application. There current_number must be protected against shared
390 * access. A first naive implementation would be:
393 * <title>The wrong way to write a thread-safe function</title>
396 * give_me_next_number (void)
398 * static int current_number = 0;
400 * static GMutex * mutex = NULL;
402 * if (!mutex) mutex = g_mutex_new (<!-- -->);
404 * g_mutex_lock (mutex);
405 * ret_val = current_number = calc_next_number (current_number);
406 * g_mutex_unlock (mutex);
413 * This looks like it would work, but there is a race condition while
414 * constructing the mutex and this code cannot work reliable. Please do
415 * not use such constructs in your own programs! One working solution
419 * <title>A correct thread-safe function</title>
421 * static GMutex *give_me_next_number_mutex = NULL;
423 * /<!-- -->* this function must be called before any call to
424 * * give_me_next_number(<!-- -->)
426 * * it must be called exactly once.
429 * init_give_me_next_number (void)
431 * g_assert (give_me_next_number_mutex == NULL);
432 * give_me_next_number_mutex = g_mutex_new (<!-- -->);
436 * give_me_next_number (void)
438 * static int current_number = 0;
441 * g_mutex_lock (give_me_next_number_mutex);
442 * ret_val = current_number = calc_next_number (current_number);
443 * g_mutex_unlock (give_me_next_number_mutex);
450 * #GStaticMutex provides a simpler and safer way of doing this.
452 * If you want to use a mutex, and your code should also work without
453 * calling g_thread_init() first, then you cannot use a #GMutex, as
454 * g_mutex_new() requires that the thread system be initialized. Use a
455 * #GStaticMutex instead.
457 * A #GMutex should only be accessed via the following functions.
460 (GMutex*(*)())g_thread_fail,
466 /* GCond Virtual Functions {{{2 ------------------------------------------ */
471 * The #GCond struct is an opaque data structure that represents a
472 * condition. Threads can block on a #GCond if they find a certain
473 * condition to be false. If other threads change the state of this
474 * condition they signal the #GCond, and that causes the waiting
475 * threads to be woken up.
479 * Using GCond to block a thread until a condition is satisfied
482 * GCond* data_cond = NULL; /<!-- -->* Must be initialized somewhere *<!-- -->/
483 * GMutex* data_mutex = NULL; /<!-- -->* Must be initialized somewhere *<!-- -->/
484 * gpointer current_data = NULL;
487 * push_data (gpointer data)
489 * g_mutex_lock (data_mutex);
490 * current_data = data;
491 * g_cond_signal (data_cond);
492 * g_mutex_unlock (data_mutex);
500 * g_mutex_lock (data_mutex);
501 * while (!current_data)
502 * g_cond_wait (data_cond, data_mutex);
503 * data = current_data;
504 * current_data = NULL;
505 * g_mutex_unlock (data_mutex);
512 * Whenever a thread calls <function>pop_data()</function> now, it will
513 * wait until current_data is non-%NULL, i.e. until some other thread
514 * has called <function>push_data()</function>.
516 * <note><para>It is important to use the g_cond_wait() and
517 * g_cond_timed_wait() functions only inside a loop which checks for the
518 * condition to be true. It is not guaranteed that the waiting thread
519 * will find the condition fulfilled after it wakes up, even if the
520 * signaling thread left the condition in that state: another thread may
521 * have altered the condition before the waiting thread got the chance
522 * to be woken up, even if the condition itself is protected by a
523 * #GMutex, like above.</para></note>
525 * A #GCond should only be accessed via the following functions.
528 (GCond*(*)())g_thread_fail,
535 /* GPrivate Virtual Functions {{{2 --------------------------------------- */
541 * #GStaticPrivate is a better choice for most uses.
544 * The #GPrivate struct is an opaque data structure to represent a
545 * thread private data key. Threads can thereby obtain and set a
546 * pointer which is private to the current thread. Take our
547 * <function>give_me_next_number(<!-- -->)</function> example from
548 * above. Suppose we don't want <literal>current_number</literal> to be
549 * shared between the threads, but instead to be private to each thread.
550 * This can be done as follows:
553 * <title>Using GPrivate for per-thread data</title>
555 * GPrivate* current_number_key = NULL; /<!-- -->* Must be initialized somewhere
556 * with g_private_new (g_free); *<!-- -->/
559 * give_me_next_number (void)
561 * int *current_number = g_private_get (current_number_key);
563 * if (!current_number)
565 * current_number = g_new (int, 1);
566 * *current_number = 0;
567 * g_private_set (current_number_key, current_number);
570 * *current_number = calc_next_number (*current_number);
572 * return *current_number;
577 * Here the pointer belonging to the key
578 * <literal>current_number_key</literal> is read. If it is %NULL, it has
579 * not been set yet. Then get memory for an integer value, assign this
580 * memory to the pointer and write the pointer back. Now we have an
581 * integer value that is private to the current thread.
583 * The #GPrivate struct should only be accessed via the following
586 * <note><para>All of the <function>g_private_*</function> functions are
587 * actually macros. Apart from taking their addresses, you can however
588 * use them as if they were functions.</para></note>
591 (GPrivate*(*)(GDestroyNotify))g_thread_fail,
595 /* GThread Virtual Functions {{{2 ---------------------------------------- */
599 * The #GThread struct represents a running thread. It has three public
600 * read-only members, but the underlying struct is bigger, so you must
601 * not copy this struct.
603 * <note><para>Resources for a joinable thread are not fully released
604 * until g_thread_join() is called for that thread.</para></note>
609 * @data: data passed to the thread.
610 * @Returns: the return value of the thread, which will be returned by
613 * Specifies the type of the @func functions passed to
614 * g_thread_create() or g_thread_create_full().
619 * @G_THREAD_PRIORITY_LOW: a priority lower than normal
620 * @G_THREAD_PRIORITY_NORMAL: the default priority
621 * @G_THREAD_PRIORITY_HIGH: a priority higher than normal
622 * @G_THREAD_PRIORITY_URGENT: the highest priority
624 * Specifies the priority of a thread.
626 * <note><para>It is not guaranteed that threads with different priorities
627 * really behave accordingly. On some systems (e.g. Linux) there are no
628 * thread priorities. On other systems (e.g. Solaris) there doesn't
629 * seem to be different scheduling for different priorities. All in all
630 * try to avoid being dependent on priorities.</para></note>
633 (void(*)(GThreadFunc, gpointer, gulong,
634 gboolean, gboolean, GThreadPriority,
635 gpointer, GError**))g_thread_fail,
637 NULL, /* thread_yield */
638 NULL, /* thread_join */
639 NULL, /* thread_exit */
640 NULL, /* thread_set_priority */
641 NULL, /* thread_self */
642 NULL /* thread_equal */
645 /* Local Data {{{1 -------------------------------------------------------- */
647 static GMutex g_once_mutex = G_MUTEX_INIT;
648 static GCond g_once_cond = G_COND_INIT;
649 static GPrivate g_thread_specific_private;
650 static GRealThread *g_thread_all_threads = NULL;
651 static GSList *g_thread_free_indices = NULL;
652 static GSList* g_once_init_list = NULL;
654 G_LOCK_DEFINE_STATIC (g_thread);
656 /* Initialisation {{{1 ---------------------------------------------------- */
660 * @vtable: a function table of type #GThreadFunctions, that provides
661 * the entry points to the thread system to be used.
663 * If you use GLib from more than one thread, you must initialize the
664 * thread system by calling g_thread_init(). Most of the time you will
665 * only have to call <literal>g_thread_init (NULL)</literal>.
667 * <note><para>Do not call g_thread_init() with a non-%NULL parameter unless
668 * you really know what you are doing.</para></note>
670 * <note><para>g_thread_init() must not be called directly or indirectly as a
671 * callback from GLib. Also no mutexes may be currently locked while
672 * calling g_thread_init().</para></note>
674 * <note><para>g_thread_init() changes the way in which #GTimer measures
675 * elapsed time. As a consequence, timers that are running while
676 * g_thread_init() is called may report unreliable times.</para></note>
678 * Calling g_thread_init() multiple times is allowed (since version
679 * 2.24), but nothing happens except for the first call. If the
680 * argument is non-%NULL on such a call a warning will be printed, but
681 * otherwise the argument is ignored.
683 * If no thread system is available and @vtable is %NULL or if not all
684 * elements of @vtable are non-%NULL, then g_thread_init() will abort.
686 * <note><para>To use g_thread_init() in your program, you have to link with
687 * the libraries that the command <command>pkg-config --libs
688 * gthread-2.0</command> outputs. This is not the case for all the
689 * other thread related functions of GLib. Those can be used without
690 * having to link with the thread libraries.</para></note>
693 /* This must be called only once, before any threads are created.
694 * It will only be called from g_thread_init() in -lgthread.
697 g_thread_init_glib (void)
699 static gboolean already_done;
706 _g_thread_impl_init ();
708 /* We let the main thread (the one that calls g_thread_init) inherit
709 * the static_private data set before calling g_thread_init
711 GRealThread* main_thread = (GRealThread*) g_thread_self ();
713 /* setup the basic threading system */
714 g_threads_got_initialized = TRUE;
715 g_private_init (&g_thread_specific_private, g_thread_cleanup);
716 g_private_set (&g_thread_specific_private, main_thread);
717 G_THREAD_UF (thread_self, (&main_thread->system_thread));
719 /* accomplish log system initialization to enable messaging */
720 _g_messages_thread_init_nomessage ();
723 /* The following sections implement: GOnce, GStaticMutex, GStaticRecMutex,
727 /* GOnce {{{1 ------------------------------------------------------------- */
731 * @status: the status of the #GOnce
732 * @retval: the value returned by the call to the function, if @status
733 * is %G_ONCE_STATUS_READY
735 * A #GOnce struct controls a one-time initialization function. Any
736 * one-time initialization function must have its own unique #GOnce
745 * A #GOnce must be initialized with this macro before it can be used.
749 * GOnce my_once = G_ONCE_INIT;
758 * @G_ONCE_STATUS_NOTCALLED: the function has not been called yet.
759 * @G_ONCE_STATUS_PROGRESS: the function call is currently in progress.
760 * @G_ONCE_STATUS_READY: the function has been called.
762 * The possible statuses of a one-time initialization function
763 * controlled by a #GOnce struct.
770 * @once: a #GOnce structure
771 * @func: the #GThreadFunc function associated to @once. This function
772 * is called only once, regardless of the number of times it and
773 * its associated #GOnce struct are passed to g_once().
774 * @arg: data to be passed to @func
776 * The first call to this routine by a process with a given #GOnce
777 * struct calls @func with the given argument. Thereafter, subsequent
778 * calls to g_once() with the same #GOnce struct do not call @func
779 * again, but return the stored result of the first call. On return
780 * from g_once(), the status of @once will be %G_ONCE_STATUS_READY.
782 * For example, a mutex or a thread-specific data key must be created
783 * exactly once. In a threaded environment, calling g_once() ensures
784 * that the initialization is serialized across multiple threads.
786 * <note><para>Calling g_once() recursively on the same #GOnce struct in
787 * @func will lead to a deadlock.</para></note>
792 * get_debug_flags (void)
794 * static GOnce my_once = G_ONCE_INIT;
796 * g_once (&my_once, parse_debug_flags, NULL);
798 * return my_once.retval;
806 g_once_impl (GOnce *once,
810 g_mutex_lock (&g_once_mutex);
812 while (once->status == G_ONCE_STATUS_PROGRESS)
813 g_cond_wait (&g_once_cond, &g_once_mutex);
815 if (once->status != G_ONCE_STATUS_READY)
817 once->status = G_ONCE_STATUS_PROGRESS;
818 g_mutex_unlock (&g_once_mutex);
820 once->retval = func (arg);
822 g_mutex_lock (&g_once_mutex);
823 once->status = G_ONCE_STATUS_READY;
824 g_cond_broadcast (&g_once_cond);
827 g_mutex_unlock (&g_once_mutex);
834 * @value_location: location of a static initializable variable
836 * @Returns: %TRUE if the initialization section should be entered,
837 * %FALSE and blocks otherwise
839 * Function to be called when starting a critical initialization
840 * section. The argument @value_location must point to a static
841 * 0-initialized variable that will be set to a value other than 0 at
842 * the end of the initialization section. In combination with
843 * g_once_init_leave() and the unique address @value_location, it can
844 * be ensured that an initialization section will be executed only once
845 * during a program's life time, and that concurrent threads are
846 * blocked until initialization completed. To be used in constructs
851 * static gsize initialization_value = 0;
853 * if (g_once_init_enter (&initialization_value))
855 * gsize setup_value = 42; /<!-- -->* initialization code here *<!-- -->/
857 * g_once_init_leave (&initialization_value, setup_value);
860 * /<!-- -->* use initialization_value here *<!-- -->/
867 g_once_init_enter_impl (volatile gsize *value_location)
869 gboolean need_init = FALSE;
870 g_mutex_lock (&g_once_mutex);
871 if (g_atomic_pointer_get (value_location) == NULL)
873 if (!g_slist_find (g_once_init_list, (void*) value_location))
876 g_once_init_list = g_slist_prepend (g_once_init_list, (void*) value_location);
880 g_cond_wait (&g_once_cond, &g_once_mutex);
881 while (g_slist_find (g_once_init_list, (void*) value_location));
883 g_mutex_unlock (&g_once_mutex);
889 * @value_location: location of a static initializable variable
891 * @initialization_value: new non-0 value for *@value_location.
893 * Counterpart to g_once_init_enter(). Expects a location of a static
894 * 0-initialized initialization variable, and an initialization value
895 * other than 0. Sets the variable to the initialization value, and
896 * releases concurrent threads blocking in g_once_init_enter() on this
897 * initialization variable.
902 g_once_init_leave (volatile gsize *value_location,
903 gsize initialization_value)
905 g_return_if_fail (g_atomic_pointer_get (value_location) == NULL);
906 g_return_if_fail (initialization_value != 0);
907 g_return_if_fail (g_once_init_list != NULL);
909 g_atomic_pointer_set (value_location, initialization_value);
910 g_mutex_lock (&g_once_mutex);
911 g_once_init_list = g_slist_remove (g_once_init_list, (void*) value_location);
912 g_cond_broadcast (&g_once_cond);
913 g_mutex_unlock (&g_once_mutex);
916 /* GStaticMutex {{{1 ------------------------------------------------------ */
921 * A #GStaticMutex works like a #GMutex, but it has one significant
922 * advantage. It doesn't need to be created at run-time like a #GMutex,
923 * but can be defined at compile-time. Here is a shorter, easier and
924 * safer version of our <function>give_me_next_number()</function>
929 * Using <structname>GStaticMutex</structname>
930 * to simplify thread-safe programming
934 * give_me_next_number (void)
936 * static int current_number = 0;
938 * static GStaticMutex mutex = G_STATIC_MUTEX_INIT;
940 * g_static_mutex_lock (&mutex);
941 * ret_val = current_number = calc_next_number (current_number);
942 * g_static_mutex_unlock (&mutex);
949 * Sometimes you would like to dynamically create a mutex. If you don't
950 * want to require prior calling to g_thread_init(), because your code
951 * should also be usable in non-threaded programs, you are not able to
952 * use g_mutex_new() and thus #GMutex, as that requires a prior call to
953 * g_thread_init(). In theses cases you can also use a #GStaticMutex.
954 * It must be initialized with g_static_mutex_init() before using it
955 * and freed with with g_static_mutex_free() when not needed anymore to
956 * free up any allocated resources.
958 * Even though #GStaticMutex is not opaque, it should only be used with
959 * the following functions, as it is defined differently on different
962 * All of the <function>g_static_mutex_*</function> functions apart
963 * from <function>g_static_mutex_get_mutex</function> can also be used
964 * even if g_thread_init() has not yet been called. Then they do
965 * nothing, apart from <function>g_static_mutex_trylock</function>,
966 * which does nothing but returning %TRUE.
968 * <note><para>All of the <function>g_static_mutex_*</function>
969 * functions are actually macros. Apart from taking their addresses, you
970 * can however use them as if they were functions.</para></note>
974 * G_STATIC_MUTEX_INIT:
976 * A #GStaticMutex must be initialized with this macro, before it can
977 * be used. This macro can used be to initialize a variable, but it
978 * cannot be assigned to a variable. In that case you have to use
979 * g_static_mutex_init().
983 * GStaticMutex my_mutex = G_STATIC_MUTEX_INIT;
989 * g_static_mutex_init:
990 * @mutex: a #GStaticMutex to be initialized.
992 * Initializes @mutex. Alternatively you can initialize it with
993 * #G_STATIC_MUTEX_INIT.
996 g_static_mutex_init (GStaticMutex *mutex)
998 static const GStaticMutex init_mutex = G_STATIC_MUTEX_INIT;
1000 g_return_if_fail (mutex);
1002 *mutex = init_mutex;
1005 /* IMPLEMENTATION NOTE:
1007 * On some platforms a GStaticMutex is actually a normal GMutex stored
1008 * inside of a structure instead of being allocated dynamically. We can
1009 * only do this for platforms on which we know, in advance, how to
1010 * allocate (size) and initialise (value) that memory.
1012 * On other platforms, a GStaticMutex is nothing more than a pointer to
1013 * a GMutex. In that case, the first access we make to the static mutex
1014 * must first allocate the normal GMutex and store it into the pointer.
1016 * configure.ac writes macros into glibconfig.h to determine if
1017 * g_static_mutex_get_mutex() accesses the structure in memory directly
1018 * (on platforms where we are able to do that) or if it ends up here,
1019 * where we may have to allocate the GMutex before returning it.
1023 * g_static_mutex_get_mutex:
1024 * @mutex: a #GStaticMutex.
1025 * @Returns: the #GMutex corresponding to @mutex.
1027 * For some operations (like g_cond_wait()) you must have a #GMutex
1028 * instead of a #GStaticMutex. This function will return the
1029 * corresponding #GMutex for @mutex.
1032 g_static_mutex_get_mutex_impl (GMutex** mutex)
1036 if (!g_thread_supported ())
1039 result = g_atomic_pointer_get (mutex);
1043 g_mutex_lock (&g_once_mutex);
1048 result = g_mutex_new ();
1049 g_atomic_pointer_set (mutex, result);
1052 g_mutex_unlock (&g_once_mutex);
1058 /* IMPLEMENTATION NOTE:
1060 * g_static_mutex_lock(), g_static_mutex_trylock() and
1061 * g_static_mutex_unlock() are all preprocessor macros that wrap the
1062 * corresponding g_mutex_*() function around a call to
1063 * g_static_mutex_get_mutex().
1067 * g_static_mutex_lock:
1068 * @mutex: a #GStaticMutex.
1070 * Works like g_mutex_lock(), but for a #GStaticMutex.
1074 * g_static_mutex_trylock:
1075 * @mutex: a #GStaticMutex.
1076 * @Returns: %TRUE, if the #GStaticMutex could be locked.
1078 * Works like g_mutex_trylock(), but for a #GStaticMutex.
1082 * g_static_mutex_unlock:
1083 * @mutex: a #GStaticMutex.
1085 * Works like g_mutex_unlock(), but for a #GStaticMutex.
1089 * g_static_mutex_free:
1090 * @mutex: a #GStaticMutex to be freed.
1092 * Releases all resources allocated to @mutex.
1094 * You don't have to call this functions for a #GStaticMutex with an
1095 * unbounded lifetime, i.e. objects declared 'static', but if you have
1096 * a #GStaticMutex as a member of a structure and the structure is
1097 * freed, you should also free the #GStaticMutex.
1099 * <note><para>Calling g_static_mutex_free() on a locked mutex may
1100 * result in undefined behaviour.</para></note>
1103 g_static_mutex_free (GStaticMutex* mutex)
1105 GMutex **runtime_mutex;
1107 g_return_if_fail (mutex);
1109 /* The runtime_mutex is the first (or only) member of GStaticMutex,
1110 * see both versions (of glibconfig.h) in configure.ac. Note, that
1111 * this variable is NULL, if g_thread_init() hasn't been called or
1112 * if we're using the default thread implementation and it provides
1113 * static mutexes. */
1114 runtime_mutex = ((GMutex**)mutex);
1117 g_mutex_free (*runtime_mutex);
1119 *runtime_mutex = NULL;
1122 /* ------------------------------------------------------------------------ */
1127 * A #GStaticRecMutex works like a #GStaticMutex, but it can be locked
1128 * multiple times by one thread. If you enter it n times, you have to
1129 * unlock it n times again to let other threads lock it. An exception
1130 * is the function g_static_rec_mutex_unlock_full(): that allows you to
1131 * unlock a #GStaticRecMutex completely returning the depth, (i.e. the
1132 * number of times this mutex was locked). The depth can later be used
1133 * to restore the state of the #GStaticRecMutex by calling
1134 * g_static_rec_mutex_lock_full().
1136 * Even though #GStaticRecMutex is not opaque, it should only be used
1137 * with the following functions.
1139 * All of the <function>g_static_rec_mutex_*</function> functions can
1140 * be used even if g_thread_init() has not been called. Then they do
1141 * nothing, apart from <function>g_static_rec_mutex_trylock</function>,
1142 * which does nothing but returning %TRUE.
1146 * G_STATIC_REC_MUTEX_INIT:
1148 * A #GStaticRecMutex must be initialized with this macro before it can
1149 * be used. This macro can used be to initialize a variable, but it
1150 * cannot be assigned to a variable. In that case you have to use
1151 * g_static_rec_mutex_init().
1155 * GStaticRecMutex my_mutex = G_STATIC_REC_MUTEX_INIT;
1161 * g_static_rec_mutex_init:
1162 * @mutex: a #GStaticRecMutex to be initialized.
1164 * A #GStaticRecMutex must be initialized with this function before it
1165 * can be used. Alternatively you can initialize it with
1166 * #G_STATIC_REC_MUTEX_INIT.
1169 g_static_rec_mutex_init (GStaticRecMutex *mutex)
1171 static const GStaticRecMutex init_mutex = G_STATIC_REC_MUTEX_INIT;
1173 g_return_if_fail (mutex);
1175 *mutex = init_mutex;
1179 * g_static_rec_mutex_lock:
1180 * @mutex: a #GStaticRecMutex to lock.
1182 * Locks @mutex. If @mutex is already locked by another thread, the
1183 * current thread will block until @mutex is unlocked by the other
1184 * thread. If @mutex is already locked by the calling thread, this
1185 * functions increases the depth of @mutex and returns immediately.
1188 g_static_rec_mutex_lock (GStaticRecMutex* mutex)
1192 g_return_if_fail (mutex);
1194 if (!g_thread_supported ())
1197 G_THREAD_UF (thread_self, (&self));
1199 if (g_system_thread_equal (&self, &mutex->owner))
1204 g_static_mutex_lock (&mutex->mutex);
1205 g_system_thread_assign (mutex->owner, self);
1210 * g_static_rec_mutex_trylock:
1211 * @mutex: a #GStaticRecMutex to lock.
1212 * @Returns: %TRUE, if @mutex could be locked.
1214 * Tries to lock @mutex. If @mutex is already locked by another thread,
1215 * it immediately returns %FALSE. Otherwise it locks @mutex and returns
1216 * %TRUE. If @mutex is already locked by the calling thread, this
1217 * functions increases the depth of @mutex and immediately returns
1221 g_static_rec_mutex_trylock (GStaticRecMutex* mutex)
1225 g_return_val_if_fail (mutex, FALSE);
1227 if (!g_thread_supported ())
1230 G_THREAD_UF (thread_self, (&self));
1232 if (g_system_thread_equal (&self, &mutex->owner))
1238 if (!g_static_mutex_trylock (&mutex->mutex))
1241 g_system_thread_assign (mutex->owner, self);
1247 * g_static_rec_mutex_unlock:
1248 * @mutex: a #GStaticRecMutex to unlock.
1250 * Unlocks @mutex. Another thread will be allowed to lock @mutex only
1251 * when it has been unlocked as many times as it had been locked
1252 * before. If @mutex is completely unlocked and another thread is
1253 * blocked in a g_static_rec_mutex_lock() call for @mutex, it will be
1254 * woken and can lock @mutex itself.
1257 g_static_rec_mutex_unlock (GStaticRecMutex* mutex)
1259 g_return_if_fail (mutex);
1261 if (!g_thread_supported ())
1264 if (mutex->depth > 1)
1269 g_system_thread_assign (mutex->owner, zero_thread);
1270 g_static_mutex_unlock (&mutex->mutex);
1274 * g_static_rec_mutex_lock_full:
1275 * @mutex: a #GStaticRecMutex to lock.
1276 * @depth: number of times this mutex has to be unlocked to be
1277 * completely unlocked.
1279 * Works like calling g_static_rec_mutex_lock() for @mutex @depth times.
1282 g_static_rec_mutex_lock_full (GStaticRecMutex *mutex,
1286 g_return_if_fail (mutex);
1288 if (!g_thread_supported ())
1294 G_THREAD_UF (thread_self, (&self));
1296 if (g_system_thread_equal (&self, &mutex->owner))
1298 mutex->depth += depth;
1301 g_static_mutex_lock (&mutex->mutex);
1302 g_system_thread_assign (mutex->owner, self);
1303 mutex->depth = depth;
1307 * g_static_rec_mutex_unlock_full:
1308 * @mutex: a #GStaticRecMutex to completely unlock.
1309 * @Returns: number of times @mutex has been locked by the current
1312 * Completely unlocks @mutex. If another thread is blocked in a
1313 * g_static_rec_mutex_lock() call for @mutex, it will be woken and can
1314 * lock @mutex itself. This function returns the number of times that
1315 * @mutex has been locked by the current thread. To restore the state
1316 * before the call to g_static_rec_mutex_unlock_full() you can call
1317 * g_static_rec_mutex_lock_full() with the depth returned by this
1321 g_static_rec_mutex_unlock_full (GStaticRecMutex *mutex)
1325 g_return_val_if_fail (mutex, 0);
1327 if (!g_thread_supported ())
1330 depth = mutex->depth;
1332 g_system_thread_assign (mutex->owner, zero_thread);
1334 g_static_mutex_unlock (&mutex->mutex);
1340 * g_static_rec_mutex_free:
1341 * @mutex: a #GStaticRecMutex to be freed.
1343 * Releases all resources allocated to a #GStaticRecMutex.
1345 * You don't have to call this functions for a #GStaticRecMutex with an
1346 * unbounded lifetime, i.e. objects declared 'static', but if you have
1347 * a #GStaticRecMutex as a member of a structure and the structure is
1348 * freed, you should also free the #GStaticRecMutex.
1351 g_static_rec_mutex_free (GStaticRecMutex *mutex)
1353 g_return_if_fail (mutex);
1355 g_static_mutex_free (&mutex->mutex);
1358 /* GStaticPrivate {{{1 ---------------------------------------------------- */
1363 * A #GStaticPrivate works almost like a #GPrivate, but it has one
1364 * significant advantage. It doesn't need to be created at run-time
1365 * like a #GPrivate, but can be defined at compile-time. This is
1366 * similar to the difference between #GMutex and #GStaticMutex. Now
1367 * look at our <function>give_me_next_number()</function> example with
1371 * <title>Using GStaticPrivate for per-thread data</title>
1374 * give_me_next_number (<!-- -->)
1376 * static GStaticPrivate current_number_key = G_STATIC_PRIVATE_INIT;
1377 * int *current_number = g_static_private_get (&current_number_key);
1379 * if (!current_number)
1381 * current_number = g_new (int,1);
1382 * *current_number = 0;
1383 * g_static_private_set (&current_number_key, current_number, g_free);
1386 * *current_number = calc_next_number (*current_number);
1388 * return *current_number;
1395 * G_STATIC_PRIVATE_INIT:
1397 * Every #GStaticPrivate must be initialized with this macro, before it
1402 * GStaticPrivate my_private = G_STATIC_PRIVATE_INIT;
1404 * </informalexample>
1408 * g_static_private_init:
1409 * @private_key: a #GStaticPrivate to be initialized.
1411 * Initializes @private_key. Alternatively you can initialize it with
1412 * #G_STATIC_PRIVATE_INIT.
1415 g_static_private_init (GStaticPrivate *private_key)
1417 private_key->index = 0;
1421 * g_static_private_get:
1422 * @private_key: a #GStaticPrivate.
1423 * @Returns: the corresponding pointer.
1425 * Works like g_private_get() only for a #GStaticPrivate.
1427 * This function works even if g_thread_init() has not yet been called.
1430 g_static_private_get (GStaticPrivate *private_key)
1432 GRealThread *self = (GRealThread*) g_thread_self ();
1434 gpointer ret = NULL;
1436 LOCK_PRIVATE_DATA (self);
1438 array = self->private_data;
1440 if (array && private_key->index != 0 && private_key->index <= array->len)
1441 ret = g_array_index (array, GStaticPrivateNode,
1442 private_key->index - 1).data;
1444 UNLOCK_PRIVATE_DATA (self);
1449 * g_static_private_set:
1450 * @private_key: a #GStaticPrivate.
1451 * @data: the new pointer.
1452 * @notify: a function to be called with the pointer whenever the
1453 * current thread ends or sets this pointer again.
1455 * Sets the pointer keyed to @private_key for the current thread and
1456 * the function @notify to be called with that pointer (%NULL or
1457 * non-%NULL), whenever the pointer is set again or whenever the
1458 * current thread ends.
1460 * This function works even if g_thread_init() has not yet been called.
1461 * If g_thread_init() is called later, the @data keyed to @private_key
1462 * will be inherited only by the main thread, i.e. the one that called
1465 * <note><para>@notify is used quite differently from @destructor in
1466 * g_private_new().</para></note>
1469 g_static_private_set (GStaticPrivate *private_key,
1471 GDestroyNotify notify)
1473 GRealThread *self = (GRealThread*) g_thread_self ();
1475 static guint next_index = 0;
1476 GStaticPrivateNode *node;
1477 gpointer ddata = NULL;
1478 GDestroyNotify ddestroy = NULL;
1480 if (!private_key->index)
1484 if (!private_key->index)
1486 if (g_thread_free_indices)
1488 private_key->index =
1489 GPOINTER_TO_UINT (g_thread_free_indices->data);
1490 g_thread_free_indices =
1491 g_slist_delete_link (g_thread_free_indices,
1492 g_thread_free_indices);
1495 private_key->index = ++next_index;
1498 G_UNLOCK (g_thread);
1501 LOCK_PRIVATE_DATA (self);
1503 array = self->private_data;
1506 array = g_array_new (FALSE, TRUE, sizeof (GStaticPrivateNode));
1507 self->private_data = array;
1510 if (private_key->index > array->len)
1511 g_array_set_size (array, private_key->index);
1513 node = &g_array_index (array, GStaticPrivateNode, private_key->index - 1);
1516 ddestroy = node->destroy;
1519 node->destroy = notify;
1521 UNLOCK_PRIVATE_DATA (self);
1528 * g_static_private_free:
1529 * @private_key: a #GStaticPrivate to be freed.
1531 * Releases all resources allocated to @private_key.
1533 * You don't have to call this functions for a #GStaticPrivate with an
1534 * unbounded lifetime, i.e. objects declared 'static', but if you have
1535 * a #GStaticPrivate as a member of a structure and the structure is
1536 * freed, you should also free the #GStaticPrivate.
1539 g_static_private_free (GStaticPrivate *private_key)
1541 guint idx = private_key->index;
1542 GRealThread *thread, *next;
1543 GArray *garbage = NULL;
1548 private_key->index = 0;
1552 thread = g_thread_all_threads;
1554 for (thread = g_thread_all_threads; thread; thread = next)
1558 next = thread->next;
1560 LOCK_PRIVATE_DATA (thread);
1562 array = thread->private_data;
1564 if (array && idx <= array->len)
1566 GStaticPrivateNode *node = &g_array_index (array,
1569 gpointer ddata = node->data;
1570 GDestroyNotify ddestroy = node->destroy;
1573 node->destroy = NULL;
1577 /* defer non-trivial destruction til after we've finished
1578 * iterating, since we must continue to hold the lock */
1579 if (garbage == NULL)
1580 garbage = g_array_new (FALSE, TRUE,
1581 sizeof (GStaticPrivateNode));
1583 g_array_set_size (garbage, garbage->len + 1);
1585 node = &g_array_index (garbage, GStaticPrivateNode,
1588 node->destroy = ddestroy;
1592 UNLOCK_PRIVATE_DATA (thread);
1594 g_thread_free_indices = g_slist_prepend (g_thread_free_indices,
1595 GUINT_TO_POINTER (idx));
1596 G_UNLOCK (g_thread);
1602 for (i = 0; i < garbage->len; i++)
1604 GStaticPrivateNode *node;
1606 node = &g_array_index (garbage, GStaticPrivateNode, i);
1607 node->destroy (node->data);
1610 g_array_free (garbage, TRUE);
1614 /* GThread Extra Functions {{{1 ------------------------------------------- */
1616 g_thread_cleanup (gpointer data)
1620 GRealThread* thread = data;
1623 LOCK_PRIVATE_DATA (thread);
1624 array = thread->private_data;
1625 thread->private_data = NULL;
1626 UNLOCK_PRIVATE_DATA (thread);
1632 for (i = 0; i < array->len; i++ )
1634 GStaticPrivateNode *node =
1635 &g_array_index (array, GStaticPrivateNode, i);
1637 node->destroy (node->data);
1639 g_array_free (array, TRUE);
1642 /* We only free the thread structure, if it isn't joinable. If
1643 it is, the structure is freed in g_thread_join */
1644 if (!thread->thread.joinable)
1649 for (t = g_thread_all_threads, p = NULL; t; p = t, t = t->next)
1656 g_thread_all_threads = t->next;
1660 G_UNLOCK (g_thread);
1662 /* Just to make sure, this isn't used any more */
1663 g_system_thread_assign (thread->system_thread, zero_thread);
1670 g_thread_fail (void)
1672 g_error ("The thread system is not yet initialized.");
1675 #define G_NSEC_PER_SEC 1000000000
1680 return g_get_monotonic_time () * 1000;
1684 g_thread_create_proxy (gpointer data)
1686 GRealThread* thread = data;
1690 /* This has to happen before G_LOCK, as that might call g_thread_self */
1691 g_private_set (&g_thread_specific_private, data);
1693 /* the lock makes sure, that thread->system_thread is written,
1694 before thread->thread.func is called. See g_thread_create. */
1696 G_UNLOCK (g_thread);
1698 thread->retval = thread->thread.func (thread->thread.data);
1705 * @func: a function to execute in the new thread
1706 * @data: an argument to supply to the new thread
1707 * @joinable: should this thread be joinable?
1708 * @error: return location for error, or %NULL
1710 * This function creates a new thread with the default priority.
1712 * If @joinable is %TRUE, you can wait for this threads termination
1713 * calling g_thread_join(). Otherwise the thread will just disappear
1714 * when it terminates.
1716 * The new thread executes the function @func with the argument @data.
1717 * If the thread was created successfully, it is returned.
1719 * @error can be %NULL to ignore errors, or non-%NULL to report errors.
1720 * The error is set, if and only if the function returns %NULL.
1722 * Returns: the new #GThread on success
1726 * g_thread_create_full:
1727 * @func: a function to execute in the new thread.
1728 * @data: an argument to supply to the new thread.
1729 * @stack_size: a stack size for the new thread.
1730 * @joinable: should this thread be joinable?
1731 * @bound: should this thread be bound to a system thread?
1732 * @priority: a priority for the thread.
1733 * @error: return location for error.
1734 * @Returns: the new #GThread on success.
1736 * This function creates a new thread with the priority @priority. If
1737 * the underlying thread implementation supports it, the thread gets a
1738 * stack size of @stack_size or the default value for the current
1739 * platform, if @stack_size is 0.
1741 * If @joinable is %TRUE, you can wait for this threads termination
1742 * calling g_thread_join(). Otherwise the thread will just disappear
1743 * when it terminates. If @bound is %TRUE, this thread will be
1744 * scheduled in the system scope, otherwise the implementation is free
1745 * to do scheduling in the process scope. The first variant is more
1746 * expensive resource-wise, but generally faster. On some systems (e.g.
1747 * Linux) all threads are bound.
1749 * The new thread executes the function @func with the argument @data.
1750 * If the thread was created successfully, it is returned.
1752 * @error can be %NULL to ignore errors, or non-%NULL to report errors.
1753 * The error is set, if and only if the function returns %NULL.
1755 * <note><para>It is not guaranteed that threads with different priorities
1756 * really behave accordingly. On some systems (e.g. Linux) there are no
1757 * thread priorities. On other systems (e.g. Solaris) there doesn't
1758 * seem to be different scheduling for different priorities. All in all
1759 * try to avoid being dependent on priorities. Use
1760 * %G_THREAD_PRIORITY_NORMAL here as a default.</para></note>
1762 * <note><para>Only use g_thread_create_full() if you really can't use
1763 * g_thread_create() instead. g_thread_create() does not take
1764 * @stack_size, @bound, and @priority as arguments, as they should only
1765 * be used in cases in which it is unavoidable.</para></note>
1768 g_thread_create_full (GThreadFunc func,
1773 GThreadPriority priority,
1776 GRealThread* result;
1777 GError *local_error = NULL;
1778 g_return_val_if_fail (func, NULL);
1779 g_return_val_if_fail (priority >= G_THREAD_PRIORITY_LOW, NULL);
1780 g_return_val_if_fail (priority <= G_THREAD_PRIORITY_URGENT, NULL);
1782 result = g_new0 (GRealThread, 1);
1784 result->thread.joinable = joinable;
1785 result->thread.priority = priority;
1786 result->thread.func = func;
1787 result->thread.data = data;
1788 result->private_data = NULL;
1790 G_THREAD_UF (thread_create, (g_thread_create_proxy, result,
1791 stack_size, joinable, bound, priority,
1792 &result->system_thread, &local_error));
1795 result->next = g_thread_all_threads;
1796 g_thread_all_threads = result;
1798 G_UNLOCK (g_thread);
1802 g_propagate_error (error, local_error);
1807 return (GThread*) result;
1812 * @retval: the return value of this thread.
1814 * Exits the current thread. If another thread is waiting for that
1815 * thread using g_thread_join() and the current thread is joinable, the
1816 * waiting thread will be woken up and get @retval as the return value
1817 * of g_thread_join(). If the current thread is not joinable, @retval
1818 * is ignored. Calling
1821 * g_thread_exit (retval);
1824 * is equivalent to returning @retval from the function @func, as given
1825 * to g_thread_create().
1827 * <note><para>Never call g_thread_exit() from within a thread of a
1828 * #GThreadPool, as that will mess up the bookkeeping and lead to funny
1829 * and unwanted results.</para></note>
1832 g_thread_exit (gpointer retval)
1834 GRealThread* real = (GRealThread*) g_thread_self ();
1835 real->retval = retval;
1837 g_system_thread_exit ();
1842 * @thread: a #GThread to be waited for.
1843 * @Returns: the return value of the thread.
1845 * Waits until @thread finishes, i.e. the function @func, as given to
1846 * g_thread_create(), returns or g_thread_exit() is called by @thread.
1847 * All resources of @thread including the #GThread struct are released.
1848 * @thread must have been created with @joinable=%TRUE in
1849 * g_thread_create(). The value returned by @func or given to
1850 * g_thread_exit() by @thread is returned by this function.
1853 g_thread_join (GThread* thread)
1855 GRealThread* real = (GRealThread*) thread;
1859 g_return_val_if_fail (thread, NULL);
1860 g_return_val_if_fail (thread->joinable, NULL);
1861 g_return_val_if_fail (!g_system_thread_equal (&real->system_thread, &zero_thread), NULL);
1863 G_THREAD_UF (thread_join, (&real->system_thread));
1865 retval = real->retval;
1868 for (t = g_thread_all_threads, p = NULL; t; p = t, t = t->next)
1870 if (t == (GRealThread*) thread)
1875 g_thread_all_threads = t->next;
1879 G_UNLOCK (g_thread);
1881 /* Just to make sure, this isn't used any more */
1882 thread->joinable = 0;
1883 g_system_thread_assign (real->system_thread, zero_thread);
1885 /* the thread structure for non-joinable threads is freed upon
1886 thread end. We free the memory here. This will leave a loose end,
1887 if a joinable thread is not joined. */
1895 * g_thread_set_priority:
1896 * @thread: a #GThread.
1897 * @priority: a new priority for @thread.
1899 * Changes the priority of @thread to @priority.
1901 * <note><para>It is not guaranteed that threads with different
1902 * priorities really behave accordingly. On some systems (e.g. Linux)
1903 * there are no thread priorities. On other systems (e.g. Solaris) there
1904 * doesn't seem to be different scheduling for different priorities. All
1905 * in all try to avoid being dependent on priorities.</para></note>
1908 g_thread_set_priority (GThread* thread,
1909 GThreadPriority priority)
1911 GRealThread* real = (GRealThread*) thread;
1913 g_return_if_fail (thread);
1914 g_return_if_fail (!g_system_thread_equal (&real->system_thread, &zero_thread));
1915 g_return_if_fail (priority >= G_THREAD_PRIORITY_LOW);
1916 g_return_if_fail (priority <= G_THREAD_PRIORITY_URGENT);
1918 thread->priority = priority;
1920 G_THREAD_CF (thread_set_priority, (void)0,
1921 (&real->system_thread, priority));
1926 * @Returns: the current thread.
1928 * This functions returns the #GThread corresponding to the calling
1932 g_thread_self (void)
1934 GRealThread* thread = g_private_get (&g_thread_specific_private);
1938 /* If no thread data is available, provide and set one. This
1939 can happen for the main thread and for threads, that are not
1941 thread = g_new0 (GRealThread, 1);
1942 thread->thread.joinable = FALSE; /* This is a save guess */
1943 thread->thread.priority = G_THREAD_PRIORITY_NORMAL; /* This is
1945 thread->thread.func = NULL;
1946 thread->thread.data = NULL;
1947 thread->private_data = NULL;
1949 G_THREAD_UF (thread_self, (&thread->system_thread));
1951 g_private_set (&g_thread_specific_private, thread);
1954 thread->next = g_thread_all_threads;
1955 g_thread_all_threads = thread;
1956 G_UNLOCK (g_thread);
1959 return (GThread*)thread;
1962 /* GStaticRWLock {{{1 ----------------------------------------------------- */
1967 * The #GStaticRWLock struct represents a read-write lock. A read-write
1968 * lock can be used for protecting data that some portions of code only
1969 * read from, while others also write. In such situations it is
1970 * desirable that several readers can read at once, whereas of course
1971 * only one writer may write at a time. Take a look at the following
1975 * <title>An array with access functions</title>
1977 * GStaticRWLock rwlock = G_STATIC_RW_LOCK_INIT;
1981 * my_array_get (guint index)
1983 * gpointer retval = NULL;
1988 * g_static_rw_lock_reader_lock (&rwlock);
1989 * if (index < array->len)
1990 * retval = g_ptr_array_index (array, index);
1991 * g_static_rw_lock_reader_unlock (&rwlock);
1997 * my_array_set (guint index, gpointer data)
1999 * g_static_rw_lock_writer_lock (&rwlock);
2002 * array = g_ptr_array_new (<!-- -->);
2004 * if (index >= array->len)
2005 * g_ptr_array_set_size (array, index+1);
2006 * g_ptr_array_index (array, index) = data;
2008 * g_static_rw_lock_writer_unlock (&rwlock);
2013 * This example shows an array which can be accessed by many readers
2014 * (the <function>my_array_get()</function> function) simultaneously,
2015 * whereas the writers (the <function>my_array_set()</function>
2016 * function) will only be allowed once at a time and only if no readers
2017 * currently access the array. This is because of the potentially
2018 * dangerous resizing of the array. Using these functions is fully
2019 * multi-thread safe now.
2021 * Most of the time, writers should have precedence over readers. That
2022 * means, for this implementation, that as soon as a writer wants to
2023 * lock the data, no other reader is allowed to lock the data, whereas,
2024 * of course, the readers that already have locked the data are allowed
2025 * to finish their operation. As soon as the last reader unlocks the
2026 * data, the writer will lock it.
2028 * Even though #GStaticRWLock is not opaque, it should only be used
2029 * with the following functions.
2031 * All of the <function>g_static_rw_lock_*</function> functions can be
2032 * used even if g_thread_init() has not been called. Then they do
2033 * nothing, apart from <function>g_static_rw_lock_*_trylock</function>,
2034 * which does nothing but returning %TRUE.
2036 * <note><para>A read-write lock has a higher overhead than a mutex. For
2037 * example, both g_static_rw_lock_reader_lock() and
2038 * g_static_rw_lock_reader_unlock() have to lock and unlock a
2039 * #GStaticMutex, so it takes at least twice the time to lock and unlock
2040 * a #GStaticRWLock that it does to lock and unlock a #GStaticMutex. So
2041 * only data structures that are accessed by multiple readers, and which
2042 * keep the lock for a considerable time justify a #GStaticRWLock. The
2043 * above example most probably would fare better with a
2044 * #GStaticMutex.</para></note>
2048 * G_STATIC_RW_LOCK_INIT:
2050 * A #GStaticRWLock must be initialized with this macro before it can
2051 * be used. This macro can used be to initialize a variable, but it
2052 * cannot be assigned to a variable. In that case you have to use
2053 * g_static_rw_lock_init().
2057 * GStaticRWLock my_lock = G_STATIC_RW_LOCK_INIT;
2059 * </informalexample>
2063 * g_static_rw_lock_init:
2064 * @lock: a #GStaticRWLock to be initialized.
2066 * A #GStaticRWLock must be initialized with this function before it
2067 * can be used. Alternatively you can initialize it with
2068 * #G_STATIC_RW_LOCK_INIT.
2071 g_static_rw_lock_init (GStaticRWLock* lock)
2073 static const GStaticRWLock init_lock = G_STATIC_RW_LOCK_INIT;
2075 g_return_if_fail (lock);
2081 g_static_rw_lock_wait (GCond** cond, GStaticMutex* mutex)
2084 *cond = g_cond_new ();
2085 g_cond_wait (*cond, g_static_mutex_get_mutex (mutex));
2089 g_static_rw_lock_signal (GStaticRWLock* lock)
2091 if (lock->want_to_write && lock->write_cond)
2092 g_cond_signal (lock->write_cond);
2093 else if (lock->want_to_read && lock->read_cond)
2094 g_cond_broadcast (lock->read_cond);
2098 * g_static_rw_lock_reader_lock:
2099 * @lock: a #GStaticRWLock to lock for reading.
2101 * Locks @lock for reading. There may be unlimited concurrent locks for
2102 * reading of a #GStaticRWLock at the same time. If @lock is already
2103 * locked for writing by another thread or if another thread is already
2104 * waiting to lock @lock for writing, this function will block until
2105 * @lock is unlocked by the other writing thread and no other writing
2106 * threads want to lock @lock. This lock has to be unlocked by
2107 * g_static_rw_lock_reader_unlock().
2109 * #GStaticRWLock is not recursive. It might seem to be possible to
2110 * recursively lock for reading, but that can result in a deadlock, due
2111 * to writer preference.
2114 g_static_rw_lock_reader_lock (GStaticRWLock* lock)
2116 g_return_if_fail (lock);
2118 if (!g_threads_got_initialized)
2121 g_static_mutex_lock (&lock->mutex);
2122 lock->want_to_read++;
2123 while (lock->have_writer || lock->want_to_write)
2124 g_static_rw_lock_wait (&lock->read_cond, &lock->mutex);
2125 lock->want_to_read--;
2126 lock->read_counter++;
2127 g_static_mutex_unlock (&lock->mutex);
2131 * g_static_rw_lock_reader_trylock:
2132 * @lock: a #GStaticRWLock to lock for reading.
2133 * @Returns: %TRUE, if @lock could be locked for reading.
2135 * Tries to lock @lock for reading. If @lock is already locked for
2136 * writing by another thread or if another thread is already waiting to
2137 * lock @lock for writing, immediately returns %FALSE. Otherwise locks
2138 * @lock for reading and returns %TRUE. This lock has to be unlocked by
2139 * g_static_rw_lock_reader_unlock().
2142 g_static_rw_lock_reader_trylock (GStaticRWLock* lock)
2144 gboolean ret_val = FALSE;
2146 g_return_val_if_fail (lock, FALSE);
2148 if (!g_threads_got_initialized)
2151 g_static_mutex_lock (&lock->mutex);
2152 if (!lock->have_writer && !lock->want_to_write)
2154 lock->read_counter++;
2157 g_static_mutex_unlock (&lock->mutex);
2162 * g_static_rw_lock_reader_unlock:
2163 * @lock: a #GStaticRWLock to unlock after reading.
2165 * Unlocks @lock. If a thread waits to lock @lock for writing and all
2166 * locks for reading have been unlocked, the waiting thread is woken up
2167 * and can lock @lock for writing.
2170 g_static_rw_lock_reader_unlock (GStaticRWLock* lock)
2172 g_return_if_fail (lock);
2174 if (!g_threads_got_initialized)
2177 g_static_mutex_lock (&lock->mutex);
2178 lock->read_counter--;
2179 if (lock->read_counter == 0)
2180 g_static_rw_lock_signal (lock);
2181 g_static_mutex_unlock (&lock->mutex);
2185 * g_static_rw_lock_writer_lock:
2186 * @lock: a #GStaticRWLock to lock for writing.
2188 * Locks @lock for writing. If @lock is already locked for writing or
2189 * reading by other threads, this function will block until @lock is
2190 * completely unlocked and then lock @lock for writing. While this
2191 * functions waits to lock @lock, no other thread can lock @lock for
2192 * reading. When @lock is locked for writing, no other thread can lock
2193 * @lock (neither for reading nor writing). This lock has to be
2194 * unlocked by g_static_rw_lock_writer_unlock().
2197 g_static_rw_lock_writer_lock (GStaticRWLock* lock)
2199 g_return_if_fail (lock);
2201 if (!g_threads_got_initialized)
2204 g_static_mutex_lock (&lock->mutex);
2205 lock->want_to_write++;
2206 while (lock->have_writer || lock->read_counter)
2207 g_static_rw_lock_wait (&lock->write_cond, &lock->mutex);
2208 lock->want_to_write--;
2209 lock->have_writer = TRUE;
2210 g_static_mutex_unlock (&lock->mutex);
2214 * g_static_rw_lock_writer_trylock:
2215 * @lock: a #GStaticRWLock to lock for writing.
2216 * @Returns: %TRUE, if @lock could be locked for writing.
2218 * Tries to lock @lock for writing. If @lock is already locked (for
2219 * either reading or writing) by another thread, it immediately returns
2220 * %FALSE. Otherwise it locks @lock for writing and returns %TRUE. This
2221 * lock has to be unlocked by g_static_rw_lock_writer_unlock().
2224 g_static_rw_lock_writer_trylock (GStaticRWLock* lock)
2226 gboolean ret_val = FALSE;
2228 g_return_val_if_fail (lock, FALSE);
2230 if (!g_threads_got_initialized)
2233 g_static_mutex_lock (&lock->mutex);
2234 if (!lock->have_writer && !lock->read_counter)
2236 lock->have_writer = TRUE;
2239 g_static_mutex_unlock (&lock->mutex);
2244 * g_static_rw_lock_writer_unlock:
2245 * @lock: a #GStaticRWLock to unlock after writing.
2247 * Unlocks @lock. If a thread is waiting to lock @lock for writing and
2248 * all locks for reading have been unlocked, the waiting thread is
2249 * woken up and can lock @lock for writing. If no thread is waiting to
2250 * lock @lock for writing, and some thread or threads are waiting to
2251 * lock @lock for reading, the waiting threads are woken up and can
2252 * lock @lock for reading.
2255 g_static_rw_lock_writer_unlock (GStaticRWLock* lock)
2257 g_return_if_fail (lock);
2259 if (!g_threads_got_initialized)
2262 g_static_mutex_lock (&lock->mutex);
2263 lock->have_writer = FALSE;
2264 g_static_rw_lock_signal (lock);
2265 g_static_mutex_unlock (&lock->mutex);
2269 * g_static_rw_lock_free:
2270 * @lock: a #GStaticRWLock to be freed.
2272 * Releases all resources allocated to @lock.
2274 * You don't have to call this functions for a #GStaticRWLock with an
2275 * unbounded lifetime, i.e. objects declared 'static', but if you have
2276 * a #GStaticRWLock as a member of a structure, and the structure is
2277 * freed, you should also free the #GStaticRWLock.
2280 g_static_rw_lock_free (GStaticRWLock* lock)
2282 g_return_if_fail (lock);
2284 if (lock->read_cond)
2286 g_cond_free (lock->read_cond);
2287 lock->read_cond = NULL;
2289 if (lock->write_cond)
2291 g_cond_free (lock->write_cond);
2292 lock->write_cond = NULL;
2294 g_static_mutex_free (&lock->mutex);
2297 /* Unsorted {{{1 ---------------------------------------------------------- */
2301 * @thread_func: function to call for all GThread structures
2302 * @user_data: second argument to @thread_func
2304 * Call @thread_func on all existing #GThread structures. Note that
2305 * threads may decide to exit while @thread_func is running, so
2306 * without intimate knowledge about the lifetime of foreign threads,
2307 * @thread_func shouldn't access the GThread* pointer passed in as
2308 * first argument. However, @thread_func will not be called for threads
2309 * which are known to have exited already.
2311 * Due to thread lifetime checks, this function has an execution complexity
2312 * which is quadratic in the number of existing threads.
2317 g_thread_foreach (GFunc thread_func,
2320 GSList *slist = NULL;
2321 GRealThread *thread;
2322 g_return_if_fail (thread_func != NULL);
2323 /* snapshot the list of threads for iteration */
2325 for (thread = g_thread_all_threads; thread; thread = thread->next)
2326 slist = g_slist_prepend (slist, thread);
2327 G_UNLOCK (g_thread);
2328 /* walk the list, skipping non-existent threads */
2331 GSList *node = slist;
2333 /* check whether the current thread still exists */
2335 for (thread = g_thread_all_threads; thread; thread = thread->next)
2336 if (thread == node->data)
2338 G_UNLOCK (g_thread);
2340 thread_func (thread, user_data);
2341 g_slist_free_1 (node);
2346 * g_thread_get_initialized:
2348 * Indicates if g_thread_init() has been called.
2350 * Returns: %TRUE if threads have been initialized.
2355 g_thread_get_initialized ()
2357 return g_thread_supported ();
2363 * Creates a new #GMutex.
2365 * Returns: a newly allocated #GMutex. Use g_mutex_free() to free
2372 mutex = g_slice_new (GMutex);
2373 g_mutex_init (mutex);
2382 * Destroys a @mutex that has been created with g_mutex_new().
2384 * <note>Calling g_mutex_free() on a locked mutex may result
2385 * in undefined behaviour.</note>
2388 g_mutex_free (GMutex *mutex)
2390 g_mutex_clear (mutex);
2391 g_slice_free (GMutex, mutex);
2397 * Creates a new #GCond.
2399 * Returns: a newly allocated #GCond. Free with g_cond_free()
2406 cond = g_slice_new (GCond);
2416 * Destroys a #GCond that has been created with g_cond_new().
2419 g_cond_free (GCond *cond)
2421 g_cond_clear (cond);
2422 g_slice_free (GCond, cond);
2427 * @destructor: a function to destroy the data keyed to
2428 * the #GPrivate when a thread ends
2430 * Creates a new #GPrivate. If @destructor is non-%NULL, it is a
2431 * pointer to a destructor function. Whenever a thread ends and the
2432 * corresponding pointer keyed to this instance of #GPrivate is
2433 * non-%NULL, the destructor is called with this pointer as the
2437 * #GStaticPrivate is a better choice for most uses.
2440 * <note><para>@destructor is used quite differently from @notify in
2441 * g_static_private_set().</para></note>
2443 * <note><para>A #GPrivate cannot be freed. Reuse it instead, if you
2444 * can, to avoid shortage, or use #GStaticPrivate.</para></note>
2446 * <note><para>This function will abort if g_thread_init() has not been
2447 * called yet.</para></note>
2449 * Returns: a newly allocated #GPrivate
2452 g_private_new (GDestroyNotify notify)
2456 key = g_slice_new (GPrivate);
2457 g_private_init (key, notify);