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.
459 * <note><para>All of the <function>g_mutex_*</function> functions are
460 * actually macros. Apart from taking their addresses, you can however
461 * use them as if they were functions.</para></note>
466 * @Returns: a new #GMutex.
468 * Creates a new #GMutex.
470 * <note><para>This function will abort if g_thread_init() has not been
471 * called yet.</para></note>
473 (GMutex*(*)())g_thread_fail,
479 * Locks @mutex. If @mutex is already locked by another thread, the
480 * current thread will block until @mutex is unlocked by the other
483 * This function can be used even if g_thread_init() has not yet been
484 * called, and, in that case, will do nothing.
486 * <note><para>#GMutex is neither guaranteed to be recursive nor to be
487 * non-recursive, i.e. a thread could deadlock while calling
488 * g_mutex_lock(), if it already has locked @mutex. Use
489 * #GStaticRecMutex, if you need recursive mutexes.</para></note>
496 * @Returns: %TRUE, if @mutex could be locked.
498 * Tries to lock @mutex. If @mutex is already locked by another thread,
499 * it immediately returns %FALSE. Otherwise it locks @mutex and returns
502 * This function can be used even if g_thread_init() has not yet been
503 * called, and, in that case, will immediately return %TRUE.
505 * <note><para>#GMutex is neither guaranteed to be recursive nor to be
506 * non-recursive, i.e. the return value of g_mutex_trylock() could be
507 * both %FALSE or %TRUE, if the current thread already has locked
508 * @mutex. Use #GStaticRecMutex, if you need recursive
509 * mutexes.</para></note>
517 * Unlocks @mutex. If another thread is blocked in a g_mutex_lock()
518 * call for @mutex, it will be woken and can lock @mutex itself.
520 * This function can be used even if g_thread_init() has not yet been
521 * called, and, in that case, will do nothing.
531 * <note><para>Calling g_mutex_free() on a locked mutex may result in
532 * undefined behaviour.</para></note>
536 /* GCond Virtual Functions {{{2 ------------------------------------------ */
541 * The #GCond struct is an opaque data structure that represents a
542 * condition. Threads can block on a #GCond if they find a certain
543 * condition to be false. If other threads change the state of this
544 * condition they signal the #GCond, and that causes the waiting
545 * threads to be woken up.
549 * Using GCond to block a thread until a condition is satisfied
552 * GCond* data_cond = NULL; /<!-- -->* Must be initialized somewhere *<!-- -->/
553 * GMutex* data_mutex = NULL; /<!-- -->* Must be initialized somewhere *<!-- -->/
554 * gpointer current_data = NULL;
557 * push_data (gpointer data)
559 * g_mutex_lock (data_mutex);
560 * current_data = data;
561 * g_cond_signal (data_cond);
562 * g_mutex_unlock (data_mutex);
570 * g_mutex_lock (data_mutex);
571 * while (!current_data)
572 * g_cond_wait (data_cond, data_mutex);
573 * data = current_data;
574 * current_data = NULL;
575 * g_mutex_unlock (data_mutex);
582 * Whenever a thread calls <function>pop_data()</function> now, it will
583 * wait until current_data is non-%NULL, i.e. until some other thread
584 * has called <function>push_data()</function>.
586 * <note><para>It is important to use the g_cond_wait() and
587 * g_cond_timed_wait() functions only inside a loop which checks for the
588 * condition to be true. It is not guaranteed that the waiting thread
589 * will find the condition fulfilled after it wakes up, even if the
590 * signaling thread left the condition in that state: another thread may
591 * have altered the condition before the waiting thread got the chance
592 * to be woken up, even if the condition itself is protected by a
593 * #GMutex, like above.</para></note>
595 * A #GCond should only be accessed via the following functions.
597 * <note><para>All of the <function>g_cond_*</function> functions are
598 * actually macros. Apart from taking their addresses, you can however
599 * use them as if they were functions.</para></note>
604 * @Returns: a new #GCond.
606 * Creates a new #GCond. This function will abort, if g_thread_init()
607 * has not been called yet.
609 (GCond*(*)())g_thread_fail,
615 * If threads are waiting for @cond, exactly one of them is woken up.
616 * It is good practice to hold the same lock as the waiting thread
617 * while calling this function, though not required.
619 * This function can be used even if g_thread_init() has not yet been
620 * called, and, in that case, will do nothing.
628 * If threads are waiting for @cond, all of them are woken up. It is
629 * good practice to lock the same mutex as the waiting threads, while
630 * calling this function, though not required.
632 * This function can be used even if g_thread_init() has not yet been
633 * called, and, in that case, will do nothing.
640 * @mutex: a #GMutex, that is currently locked.
642 * Waits until this thread is woken up on @cond. The @mutex is unlocked
643 * before falling asleep and locked again before resuming.
645 * This function can be used even if g_thread_init() has not yet been
646 * called, and, in that case, will immediately return.
653 * @mutex: a #GMutex that is currently locked.
654 * @abs_time: a #GTimeVal, determining the final time.
655 * @Returns: %TRUE if @cond was signalled, or %FALSE on timeout.
657 * Waits until this thread is woken up on @cond, but not longer than
658 * until the time specified by @abs_time. The @mutex is unlocked before
659 * falling asleep and locked again before resuming.
661 * If @abs_time is %NULL, g_cond_timed_wait() acts like g_cond_wait().
663 * This function can be used even if g_thread_init() has not yet been
664 * called, and, in that case, will immediately return %TRUE.
666 * To easily calculate @abs_time a combination of g_get_current_time()
667 * and g_time_val_add() can be used.
675 * Destroys the #GCond.
679 /* GPrivate Virtual Functions {{{2 --------------------------------------- */
685 * #GStaticPrivate is a better choice for most uses.
688 * The #GPrivate struct is an opaque data structure to represent a
689 * thread private data key. Threads can thereby obtain and set a
690 * pointer which is private to the current thread. Take our
691 * <function>give_me_next_number(<!-- -->)</function> example from
692 * above. Suppose we don't want <literal>current_number</literal> to be
693 * shared between the threads, but instead to be private to each thread.
694 * This can be done as follows:
697 * <title>Using GPrivate for per-thread data</title>
699 * GPrivate* current_number_key = NULL; /<!-- -->* Must be initialized somewhere
700 * with g_private_new (g_free); *<!-- -->/
703 * give_me_next_number (void)
705 * int *current_number = g_private_get (current_number_key);
707 * if (!current_number)
709 * current_number = g_new (int, 1);
710 * *current_number = 0;
711 * g_private_set (current_number_key, current_number);
714 * *current_number = calc_next_number (*current_number);
716 * return *current_number;
721 * Here the pointer belonging to the key
722 * <literal>current_number_key</literal> is read. If it is %NULL, it has
723 * not been set yet. Then get memory for an integer value, assign this
724 * memory to the pointer and write the pointer back. Now we have an
725 * integer value that is private to the current thread.
727 * The #GPrivate struct should only be accessed via the following
730 * <note><para>All of the <function>g_private_*</function> functions are
731 * actually macros. Apart from taking their addresses, you can however
732 * use them as if they were functions.</para></note>
737 * @destructor: a function to destroy the data keyed to #GPrivate when
739 * @Returns: a new #GPrivate.
741 * Creates a new #GPrivate. If @destructor is non-%NULL, it is a
742 * pointer to a destructor function. Whenever a thread ends and the
743 * corresponding pointer keyed to this instance of #GPrivate is
744 * non-%NULL, the destructor is called with this pointer as the
748 * #GStaticPrivate is a better choice for most uses.
751 * <note><para>@destructor is used quite differently from @notify in
752 * g_static_private_set().</para></note>
754 * <note><para>A #GPrivate cannot be freed. Reuse it instead, if you
755 * can, to avoid shortage, or use #GStaticPrivate.</para></note>
757 * <note><para>This function will abort if g_thread_init() has not been
758 * called yet.</para></note>
760 (GPrivate*(*)(GDestroyNotify))g_thread_fail,
764 * @private_key: a #GPrivate.
765 * @Returns: the corresponding pointer.
767 * Returns the pointer keyed to @private_key for the current thread. If
768 * g_private_set() hasn't been called for the current @private_key and
769 * thread yet, this pointer will be %NULL.
771 * This function can be used even if g_thread_init() has not yet been
772 * called, and, in that case, will return the value of @private_key
773 * casted to #gpointer. Note however, that private data set
774 * <emphasis>before</emphasis> g_thread_init() will
775 * <emphasis>not</emphasis> be retained <emphasis>after</emphasis> the
776 * call. Instead, %NULL will be returned in all threads directly after
777 * g_thread_init(), regardless of any g_private_set() calls issued
778 * before threading system intialization.
784 * @private_key: a #GPrivate.
785 * @data: the new pointer.
787 * Sets the pointer keyed to @private_key for the current thread.
789 * This function can be used even if g_thread_init() has not yet been
790 * called, and, in that case, will set @private_key to @data casted to
791 * #GPrivate*. See g_private_get() for resulting caveats.
795 /* GThread Virtual Functions {{{2 ---------------------------------------- */
799 * The #GThread struct represents a running thread. It has three public
800 * read-only members, but the underlying struct is bigger, so you must
801 * not copy this struct.
803 * <note><para>Resources for a joinable thread are not fully released
804 * until g_thread_join() is called for that thread.</para></note>
809 * @data: data passed to the thread.
810 * @Returns: the return value of the thread, which will be returned by
813 * Specifies the type of the @func functions passed to
814 * g_thread_create() or g_thread_create_full().
819 * @G_THREAD_PRIORITY_LOW: a priority lower than normal
820 * @G_THREAD_PRIORITY_NORMAL: the default priority
821 * @G_THREAD_PRIORITY_HIGH: a priority higher than normal
822 * @G_THREAD_PRIORITY_URGENT: the highest priority
824 * Specifies the priority of a thread.
826 * <note><para>It is not guaranteed that threads with different priorities
827 * really behave accordingly. On some systems (e.g. Linux) there are no
828 * thread priorities. On other systems (e.g. Solaris) there doesn't
829 * seem to be different scheduling for different priorities. All in all
830 * try to avoid being dependent on priorities.</para></note>
835 * @func: a function to execute in the new thread.
836 * @data: an argument to supply to the new thread.
837 * @joinable: should this thread be joinable?
838 * @error: return location for error.
839 * @Returns: the new #GThread on success.
841 * This function creates a new thread with the default priority.
843 * If @joinable is %TRUE, you can wait for this threads termination
844 * calling g_thread_join(). Otherwise the thread will just disappear
845 * when it terminates.
847 * The new thread executes the function @func with the argument @data.
848 * If the thread was created successfully, it is returned.
850 * @error can be %NULL to ignore errors, or non-%NULL to report errors.
851 * The error is set, if and only if the function returns %NULL.
853 (void(*)(GThreadFunc, gpointer, gulong,
854 gboolean, gboolean, GThreadPriority,
855 gpointer, GError**))g_thread_fail,
860 * Gives way to other threads waiting to be scheduled.
862 * This function is often used as a method to make busy wait less evil.
863 * But in most cases you will encounter, there are better methods to do
864 * that. So in general you shouldn't use this function.
868 NULL, /* thread_join */
869 NULL, /* thread_exit */
870 NULL, /* thread_set_priority */
871 NULL, /* thread_self */
872 NULL /* thread_equal */
875 /* Local Data {{{1 -------------------------------------------------------- */
877 static GMutex g_once_mutex = G_MUTEX_INIT;
878 static GCond g_once_cond = G_COND_INIT;
879 static GPrivate g_thread_specific_private;
880 static GRealThread *g_thread_all_threads = NULL;
881 static GSList *g_thread_free_indices = NULL;
882 static GSList* g_once_init_list = NULL;
884 G_LOCK_DEFINE_STATIC (g_thread);
886 /* Initialisation {{{1 ---------------------------------------------------- */
890 * @vtable: a function table of type #GThreadFunctions, that provides
891 * the entry points to the thread system to be used.
893 * If you use GLib from more than one thread, you must initialize the
894 * thread system by calling g_thread_init(). Most of the time you will
895 * only have to call <literal>g_thread_init (NULL)</literal>.
897 * <note><para>Do not call g_thread_init() with a non-%NULL parameter unless
898 * you really know what you are doing.</para></note>
900 * <note><para>g_thread_init() must not be called directly or indirectly as a
901 * callback from GLib. Also no mutexes may be currently locked while
902 * calling g_thread_init().</para></note>
904 * <note><para>g_thread_init() changes the way in which #GTimer measures
905 * elapsed time. As a consequence, timers that are running while
906 * g_thread_init() is called may report unreliable times.</para></note>
908 * Calling g_thread_init() multiple times is allowed (since version
909 * 2.24), but nothing happens except for the first call. If the
910 * argument is non-%NULL on such a call a warning will be printed, but
911 * otherwise the argument is ignored.
913 * If no thread system is available and @vtable is %NULL or if not all
914 * elements of @vtable are non-%NULL, then g_thread_init() will abort.
916 * <note><para>To use g_thread_init() in your program, you have to link with
917 * the libraries that the command <command>pkg-config --libs
918 * gthread-2.0</command> outputs. This is not the case for all the
919 * other thread related functions of GLib. Those can be used without
920 * having to link with the thread libraries.</para></note>
923 /* This must be called only once, before any threads are created.
924 * It will only be called from g_thread_init() in -lgthread.
927 g_thread_init_glib (void)
929 static gboolean already_done;
936 _g_thread_impl_init ();
938 /* We let the main thread (the one that calls g_thread_init) inherit
939 * the static_private data set before calling g_thread_init
941 GRealThread* main_thread = (GRealThread*) g_thread_self ();
943 /* setup the basic threading system */
944 g_threads_got_initialized = TRUE;
945 g_private_init (&g_thread_specific_private, g_thread_cleanup);
946 g_private_set (&g_thread_specific_private, main_thread);
947 G_THREAD_UF (thread_self, (&main_thread->system_thread));
949 /* accomplish log system initialization to enable messaging */
950 _g_messages_thread_init_nomessage ();
953 /* The following sections implement: GOnce, GStaticMutex, GStaticRecMutex,
957 /* GOnce {{{1 ------------------------------------------------------------- */
961 * @status: the status of the #GOnce
962 * @retval: the value returned by the call to the function, if @status
963 * is %G_ONCE_STATUS_READY
965 * A #GOnce struct controls a one-time initialization function. Any
966 * one-time initialization function must have its own unique #GOnce
975 * A #GOnce must be initialized with this macro before it can be used.
979 * GOnce my_once = G_ONCE_INIT;
988 * @G_ONCE_STATUS_NOTCALLED: the function has not been called yet.
989 * @G_ONCE_STATUS_PROGRESS: the function call is currently in progress.
990 * @G_ONCE_STATUS_READY: the function has been called.
992 * The possible statuses of a one-time initialization function
993 * controlled by a #GOnce struct.
1000 * @once: a #GOnce structure
1001 * @func: the #GThreadFunc function associated to @once. This function
1002 * is called only once, regardless of the number of times it and
1003 * its associated #GOnce struct are passed to g_once().
1004 * @arg: data to be passed to @func
1006 * The first call to this routine by a process with a given #GOnce
1007 * struct calls @func with the given argument. Thereafter, subsequent
1008 * calls to g_once() with the same #GOnce struct do not call @func
1009 * again, but return the stored result of the first call. On return
1010 * from g_once(), the status of @once will be %G_ONCE_STATUS_READY.
1012 * For example, a mutex or a thread-specific data key must be created
1013 * exactly once. In a threaded environment, calling g_once() ensures
1014 * that the initialization is serialized across multiple threads.
1016 * <note><para>Calling g_once() recursively on the same #GOnce struct in
1017 * @func will lead to a deadlock.</para></note>
1022 * get_debug_flags (void)
1024 * static GOnce my_once = G_ONCE_INIT;
1026 * g_once (&my_once, parse_debug_flags, NULL);
1028 * return my_once.retval;
1031 * </informalexample>
1036 g_once_impl (GOnce *once,
1040 g_mutex_lock (&g_once_mutex);
1042 while (once->status == G_ONCE_STATUS_PROGRESS)
1043 g_cond_wait (&g_once_cond, &g_once_mutex);
1045 if (once->status != G_ONCE_STATUS_READY)
1047 once->status = G_ONCE_STATUS_PROGRESS;
1048 g_mutex_unlock (&g_once_mutex);
1050 once->retval = func (arg);
1052 g_mutex_lock (&g_once_mutex);
1053 once->status = G_ONCE_STATUS_READY;
1054 g_cond_broadcast (&g_once_cond);
1057 g_mutex_unlock (&g_once_mutex);
1059 return once->retval;
1063 * g_once_init_enter:
1064 * @value_location: location of a static initializable variable
1066 * @Returns: %TRUE if the initialization section should be entered,
1067 * %FALSE and blocks otherwise
1069 * Function to be called when starting a critical initialization
1070 * section. The argument @value_location must point to a static
1071 * 0-initialized variable that will be set to a value other than 0 at
1072 * the end of the initialization section. In combination with
1073 * g_once_init_leave() and the unique address @value_location, it can
1074 * be ensured that an initialization section will be executed only once
1075 * during a program's life time, and that concurrent threads are
1076 * blocked until initialization completed. To be used in constructs
1081 * static gsize initialization_value = 0;
1083 * if (g_once_init_enter (&initialization_value))
1085 * gsize setup_value = 42; /<!-- -->* initialization code here *<!-- -->/
1087 * g_once_init_leave (&initialization_value, setup_value);
1090 * /<!-- -->* use initialization_value here *<!-- -->/
1092 * </informalexample>
1097 g_once_init_enter_impl (volatile gsize *value_location)
1099 gboolean need_init = FALSE;
1100 g_mutex_lock (&g_once_mutex);
1101 if (g_atomic_pointer_get (value_location) == NULL)
1103 if (!g_slist_find (g_once_init_list, (void*) value_location))
1106 g_once_init_list = g_slist_prepend (g_once_init_list, (void*) value_location);
1110 g_cond_wait (&g_once_cond, &g_once_mutex);
1111 while (g_slist_find (g_once_init_list, (void*) value_location));
1113 g_mutex_unlock (&g_once_mutex);
1118 * g_once_init_leave:
1119 * @value_location: location of a static initializable variable
1121 * @initialization_value: new non-0 value for *@value_location.
1123 * Counterpart to g_once_init_enter(). Expects a location of a static
1124 * 0-initialized initialization variable, and an initialization value
1125 * other than 0. Sets the variable to the initialization value, and
1126 * releases concurrent threads blocking in g_once_init_enter() on this
1127 * initialization variable.
1132 g_once_init_leave (volatile gsize *value_location,
1133 gsize initialization_value)
1135 g_return_if_fail (g_atomic_pointer_get (value_location) == NULL);
1136 g_return_if_fail (initialization_value != 0);
1137 g_return_if_fail (g_once_init_list != NULL);
1139 g_atomic_pointer_set (value_location, initialization_value);
1140 g_mutex_lock (&g_once_mutex);
1141 g_once_init_list = g_slist_remove (g_once_init_list, (void*) value_location);
1142 g_cond_broadcast (&g_once_cond);
1143 g_mutex_unlock (&g_once_mutex);
1146 /* GStaticMutex {{{1 ------------------------------------------------------ */
1151 * A #GStaticMutex works like a #GMutex, but it has one significant
1152 * advantage. It doesn't need to be created at run-time like a #GMutex,
1153 * but can be defined at compile-time. Here is a shorter, easier and
1154 * safer version of our <function>give_me_next_number()</function>
1159 * Using <structname>GStaticMutex</structname>
1160 * to simplify thread-safe programming
1164 * give_me_next_number (void)
1166 * static int current_number = 0;
1168 * static GStaticMutex mutex = G_STATIC_MUTEX_INIT;
1170 * g_static_mutex_lock (&mutex);
1171 * ret_val = current_number = calc_next_number (current_number);
1172 * g_static_mutex_unlock (&mutex);
1179 * Sometimes you would like to dynamically create a mutex. If you don't
1180 * want to require prior calling to g_thread_init(), because your code
1181 * should also be usable in non-threaded programs, you are not able to
1182 * use g_mutex_new() and thus #GMutex, as that requires a prior call to
1183 * g_thread_init(). In theses cases you can also use a #GStaticMutex.
1184 * It must be initialized with g_static_mutex_init() before using it
1185 * and freed with with g_static_mutex_free() when not needed anymore to
1186 * free up any allocated resources.
1188 * Even though #GStaticMutex is not opaque, it should only be used with
1189 * the following functions, as it is defined differently on different
1192 * All of the <function>g_static_mutex_*</function> functions apart
1193 * from <function>g_static_mutex_get_mutex</function> can also be used
1194 * even if g_thread_init() has not yet been called. Then they do
1195 * nothing, apart from <function>g_static_mutex_trylock</function>,
1196 * which does nothing but returning %TRUE.
1198 * <note><para>All of the <function>g_static_mutex_*</function>
1199 * functions are actually macros. Apart from taking their addresses, you
1200 * can however use them as if they were functions.</para></note>
1204 * G_STATIC_MUTEX_INIT:
1206 * A #GStaticMutex must be initialized with this macro, before it can
1207 * be used. This macro can used be to initialize a variable, but it
1208 * cannot be assigned to a variable. In that case you have to use
1209 * g_static_mutex_init().
1213 * GStaticMutex my_mutex = G_STATIC_MUTEX_INIT;
1215 * </informalexample>
1219 * g_static_mutex_init:
1220 * @mutex: a #GStaticMutex to be initialized.
1222 * Initializes @mutex. Alternatively you can initialize it with
1223 * #G_STATIC_MUTEX_INIT.
1226 g_static_mutex_init (GStaticMutex *mutex)
1228 static const GStaticMutex init_mutex = G_STATIC_MUTEX_INIT;
1230 g_return_if_fail (mutex);
1232 *mutex = init_mutex;
1235 /* IMPLEMENTATION NOTE:
1237 * On some platforms a GStaticMutex is actually a normal GMutex stored
1238 * inside of a structure instead of being allocated dynamically. We can
1239 * only do this for platforms on which we know, in advance, how to
1240 * allocate (size) and initialise (value) that memory.
1242 * On other platforms, a GStaticMutex is nothing more than a pointer to
1243 * a GMutex. In that case, the first access we make to the static mutex
1244 * must first allocate the normal GMutex and store it into the pointer.
1246 * configure.ac writes macros into glibconfig.h to determine if
1247 * g_static_mutex_get_mutex() accesses the structure in memory directly
1248 * (on platforms where we are able to do that) or if it ends up here,
1249 * where we may have to allocate the GMutex before returning it.
1253 * g_static_mutex_get_mutex:
1254 * @mutex: a #GStaticMutex.
1255 * @Returns: the #GMutex corresponding to @mutex.
1257 * For some operations (like g_cond_wait()) you must have a #GMutex
1258 * instead of a #GStaticMutex. This function will return the
1259 * corresponding #GMutex for @mutex.
1262 g_static_mutex_get_mutex_impl (GMutex** mutex)
1266 if (!g_thread_supported ())
1269 result = g_atomic_pointer_get (mutex);
1273 g_mutex_lock (&g_once_mutex);
1278 result = g_mutex_new ();
1279 g_atomic_pointer_set (mutex, result);
1282 g_mutex_unlock (&g_once_mutex);
1288 /* IMPLEMENTATION NOTE:
1290 * g_static_mutex_lock(), g_static_mutex_trylock() and
1291 * g_static_mutex_unlock() are all preprocessor macros that wrap the
1292 * corresponding g_mutex_*() function around a call to
1293 * g_static_mutex_get_mutex().
1297 * g_static_mutex_lock:
1298 * @mutex: a #GStaticMutex.
1300 * Works like g_mutex_lock(), but for a #GStaticMutex.
1304 * g_static_mutex_trylock:
1305 * @mutex: a #GStaticMutex.
1306 * @Returns: %TRUE, if the #GStaticMutex could be locked.
1308 * Works like g_mutex_trylock(), but for a #GStaticMutex.
1312 * g_static_mutex_unlock:
1313 * @mutex: a #GStaticMutex.
1315 * Works like g_mutex_unlock(), but for a #GStaticMutex.
1319 * g_static_mutex_free:
1320 * @mutex: a #GStaticMutex to be freed.
1322 * Releases all resources allocated to @mutex.
1324 * You don't have to call this functions for a #GStaticMutex with an
1325 * unbounded lifetime, i.e. objects declared 'static', but if you have
1326 * a #GStaticMutex as a member of a structure and the structure is
1327 * freed, you should also free the #GStaticMutex.
1329 * <note><para>Calling g_static_mutex_free() on a locked mutex may
1330 * result in undefined behaviour.</para></note>
1333 g_static_mutex_free (GStaticMutex* mutex)
1335 GMutex **runtime_mutex;
1337 g_return_if_fail (mutex);
1339 /* The runtime_mutex is the first (or only) member of GStaticMutex,
1340 * see both versions (of glibconfig.h) in configure.ac. Note, that
1341 * this variable is NULL, if g_thread_init() hasn't been called or
1342 * if we're using the default thread implementation and it provides
1343 * static mutexes. */
1344 runtime_mutex = ((GMutex**)mutex);
1347 g_mutex_free (*runtime_mutex);
1349 *runtime_mutex = NULL;
1352 /* ------------------------------------------------------------------------ */
1357 * A #GStaticRecMutex works like a #GStaticMutex, but it can be locked
1358 * multiple times by one thread. If you enter it n times, you have to
1359 * unlock it n times again to let other threads lock it. An exception
1360 * is the function g_static_rec_mutex_unlock_full(): that allows you to
1361 * unlock a #GStaticRecMutex completely returning the depth, (i.e. the
1362 * number of times this mutex was locked). The depth can later be used
1363 * to restore the state of the #GStaticRecMutex by calling
1364 * g_static_rec_mutex_lock_full().
1366 * Even though #GStaticRecMutex is not opaque, it should only be used
1367 * with the following functions.
1369 * All of the <function>g_static_rec_mutex_*</function> functions can
1370 * be used even if g_thread_init() has not been called. Then they do
1371 * nothing, apart from <function>g_static_rec_mutex_trylock</function>,
1372 * which does nothing but returning %TRUE.
1376 * G_STATIC_REC_MUTEX_INIT:
1378 * A #GStaticRecMutex must be initialized with this macro before it can
1379 * be used. This macro can used be to initialize a variable, but it
1380 * cannot be assigned to a variable. In that case you have to use
1381 * g_static_rec_mutex_init().
1385 * GStaticRecMutex my_mutex = G_STATIC_REC_MUTEX_INIT;
1391 * g_static_rec_mutex_init:
1392 * @mutex: a #GStaticRecMutex to be initialized.
1394 * A #GStaticRecMutex must be initialized with this function before it
1395 * can be used. Alternatively you can initialize it with
1396 * #G_STATIC_REC_MUTEX_INIT.
1399 g_static_rec_mutex_init (GStaticRecMutex *mutex)
1401 static const GStaticRecMutex init_mutex = G_STATIC_REC_MUTEX_INIT;
1403 g_return_if_fail (mutex);
1405 *mutex = init_mutex;
1409 * g_static_rec_mutex_lock:
1410 * @mutex: a #GStaticRecMutex to lock.
1412 * Locks @mutex. If @mutex is already locked by another thread, the
1413 * current thread will block until @mutex is unlocked by the other
1414 * thread. If @mutex is already locked by the calling thread, this
1415 * functions increases the depth of @mutex and returns immediately.
1418 g_static_rec_mutex_lock (GStaticRecMutex* mutex)
1422 g_return_if_fail (mutex);
1424 if (!g_thread_supported ())
1427 G_THREAD_UF (thread_self, (&self));
1429 if (g_system_thread_equal (self, mutex->owner))
1434 g_static_mutex_lock (&mutex->mutex);
1435 g_system_thread_assign (mutex->owner, self);
1440 * g_static_rec_mutex_trylock:
1441 * @mutex: a #GStaticRecMutex to lock.
1442 * @Returns: %TRUE, if @mutex could be locked.
1444 * Tries to lock @mutex. If @mutex is already locked by another thread,
1445 * it immediately returns %FALSE. Otherwise it locks @mutex and returns
1446 * %TRUE. If @mutex is already locked by the calling thread, this
1447 * functions increases the depth of @mutex and immediately returns
1451 g_static_rec_mutex_trylock (GStaticRecMutex* mutex)
1455 g_return_val_if_fail (mutex, FALSE);
1457 if (!g_thread_supported ())
1460 G_THREAD_UF (thread_self, (&self));
1462 if (g_system_thread_equal (self, mutex->owner))
1468 if (!g_static_mutex_trylock (&mutex->mutex))
1471 g_system_thread_assign (mutex->owner, self);
1477 * g_static_rec_mutex_unlock:
1478 * @mutex: a #GStaticRecMutex to unlock.
1480 * Unlocks @mutex. Another thread will be allowed to lock @mutex only
1481 * when it has been unlocked as many times as it had been locked
1482 * before. If @mutex is completely unlocked and another thread is
1483 * blocked in a g_static_rec_mutex_lock() call for @mutex, it will be
1484 * woken and can lock @mutex itself.
1487 g_static_rec_mutex_unlock (GStaticRecMutex* mutex)
1489 g_return_if_fail (mutex);
1491 if (!g_thread_supported ())
1494 if (mutex->depth > 1)
1499 g_system_thread_assign (mutex->owner, zero_thread);
1500 g_static_mutex_unlock (&mutex->mutex);
1504 * g_static_rec_mutex_lock_full:
1505 * @mutex: a #GStaticRecMutex to lock.
1506 * @depth: number of times this mutex has to be unlocked to be
1507 * completely unlocked.
1509 * Works like calling g_static_rec_mutex_lock() for @mutex @depth times.
1512 g_static_rec_mutex_lock_full (GStaticRecMutex *mutex,
1516 g_return_if_fail (mutex);
1518 if (!g_thread_supported ())
1524 G_THREAD_UF (thread_self, (&self));
1526 if (g_system_thread_equal (self, mutex->owner))
1528 mutex->depth += depth;
1531 g_static_mutex_lock (&mutex->mutex);
1532 g_system_thread_assign (mutex->owner, self);
1533 mutex->depth = depth;
1537 * g_static_rec_mutex_unlock_full:
1538 * @mutex: a #GStaticRecMutex to completely unlock.
1539 * @Returns: number of times @mutex has been locked by the current
1542 * Completely unlocks @mutex. If another thread is blocked in a
1543 * g_static_rec_mutex_lock() call for @mutex, it will be woken and can
1544 * lock @mutex itself. This function returns the number of times that
1545 * @mutex has been locked by the current thread. To restore the state
1546 * before the call to g_static_rec_mutex_unlock_full() you can call
1547 * g_static_rec_mutex_lock_full() with the depth returned by this
1551 g_static_rec_mutex_unlock_full (GStaticRecMutex *mutex)
1555 g_return_val_if_fail (mutex, 0);
1557 if (!g_thread_supported ())
1560 depth = mutex->depth;
1562 g_system_thread_assign (mutex->owner, zero_thread);
1564 g_static_mutex_unlock (&mutex->mutex);
1570 * g_static_rec_mutex_free:
1571 * @mutex: a #GStaticRecMutex to be freed.
1573 * Releases all resources allocated to a #GStaticRecMutex.
1575 * You don't have to call this functions for a #GStaticRecMutex with an
1576 * unbounded lifetime, i.e. objects declared 'static', but if you have
1577 * a #GStaticRecMutex as a member of a structure and the structure is
1578 * freed, you should also free the #GStaticRecMutex.
1581 g_static_rec_mutex_free (GStaticRecMutex *mutex)
1583 g_return_if_fail (mutex);
1585 g_static_mutex_free (&mutex->mutex);
1588 /* GStaticPrivate {{{1 ---------------------------------------------------- */
1593 * A #GStaticPrivate works almost like a #GPrivate, but it has one
1594 * significant advantage. It doesn't need to be created at run-time
1595 * like a #GPrivate, but can be defined at compile-time. This is
1596 * similar to the difference between #GMutex and #GStaticMutex. Now
1597 * look at our <function>give_me_next_number()</function> example with
1601 * <title>Using GStaticPrivate for per-thread data</title>
1604 * give_me_next_number (<!-- -->)
1606 * static GStaticPrivate current_number_key = G_STATIC_PRIVATE_INIT;
1607 * int *current_number = g_static_private_get (&current_number_key);
1609 * if (!current_number)
1611 * current_number = g_new (int,1);
1612 * *current_number = 0;
1613 * g_static_private_set (&current_number_key, current_number, g_free);
1616 * *current_number = calc_next_number (*current_number);
1618 * return *current_number;
1625 * G_STATIC_PRIVATE_INIT:
1627 * Every #GStaticPrivate must be initialized with this macro, before it
1632 * GStaticPrivate my_private = G_STATIC_PRIVATE_INIT;
1634 * </informalexample>
1638 * g_static_private_init:
1639 * @private_key: a #GStaticPrivate to be initialized.
1641 * Initializes @private_key. Alternatively you can initialize it with
1642 * #G_STATIC_PRIVATE_INIT.
1645 g_static_private_init (GStaticPrivate *private_key)
1647 private_key->index = 0;
1651 * g_static_private_get:
1652 * @private_key: a #GStaticPrivate.
1653 * @Returns: the corresponding pointer.
1655 * Works like g_private_get() only for a #GStaticPrivate.
1657 * This function works even if g_thread_init() has not yet been called.
1660 g_static_private_get (GStaticPrivate *private_key)
1662 GRealThread *self = (GRealThread*) g_thread_self ();
1664 gpointer ret = NULL;
1666 LOCK_PRIVATE_DATA (self);
1668 array = self->private_data;
1670 if (array && private_key->index != 0 && private_key->index <= array->len)
1671 ret = g_array_index (array, GStaticPrivateNode,
1672 private_key->index - 1).data;
1674 UNLOCK_PRIVATE_DATA (self);
1679 * g_static_private_set:
1680 * @private_key: a #GStaticPrivate.
1681 * @data: the new pointer.
1682 * @notify: a function to be called with the pointer whenever the
1683 * current thread ends or sets this pointer again.
1685 * Sets the pointer keyed to @private_key for the current thread and
1686 * the function @notify to be called with that pointer (%NULL or
1687 * non-%NULL), whenever the pointer is set again or whenever the
1688 * current thread ends.
1690 * This function works even if g_thread_init() has not yet been called.
1691 * If g_thread_init() is called later, the @data keyed to @private_key
1692 * will be inherited only by the main thread, i.e. the one that called
1695 * <note><para>@notify is used quite differently from @destructor in
1696 * g_private_new().</para></note>
1699 g_static_private_set (GStaticPrivate *private_key,
1701 GDestroyNotify notify)
1703 GRealThread *self = (GRealThread*) g_thread_self ();
1705 static guint next_index = 0;
1706 GStaticPrivateNode *node;
1707 gpointer ddata = NULL;
1708 GDestroyNotify ddestroy = NULL;
1710 if (!private_key->index)
1714 if (!private_key->index)
1716 if (g_thread_free_indices)
1718 private_key->index =
1719 GPOINTER_TO_UINT (g_thread_free_indices->data);
1720 g_thread_free_indices =
1721 g_slist_delete_link (g_thread_free_indices,
1722 g_thread_free_indices);
1725 private_key->index = ++next_index;
1728 G_UNLOCK (g_thread);
1731 LOCK_PRIVATE_DATA (self);
1733 array = self->private_data;
1736 array = g_array_new (FALSE, TRUE, sizeof (GStaticPrivateNode));
1737 self->private_data = array;
1740 if (private_key->index > array->len)
1741 g_array_set_size (array, private_key->index);
1743 node = &g_array_index (array, GStaticPrivateNode, private_key->index - 1);
1746 ddestroy = node->destroy;
1749 node->destroy = notify;
1751 UNLOCK_PRIVATE_DATA (self);
1758 * g_static_private_free:
1759 * @private_key: a #GStaticPrivate to be freed.
1761 * Releases all resources allocated to @private_key.
1763 * You don't have to call this functions for a #GStaticPrivate with an
1764 * unbounded lifetime, i.e. objects declared 'static', but if you have
1765 * a #GStaticPrivate as a member of a structure and the structure is
1766 * freed, you should also free the #GStaticPrivate.
1769 g_static_private_free (GStaticPrivate *private_key)
1771 guint idx = private_key->index;
1772 GRealThread *thread, *next;
1773 GArray *garbage = NULL;
1778 private_key->index = 0;
1782 thread = g_thread_all_threads;
1784 for (thread = g_thread_all_threads; thread; thread = next)
1788 next = thread->next;
1790 LOCK_PRIVATE_DATA (thread);
1792 array = thread->private_data;
1794 if (array && idx <= array->len)
1796 GStaticPrivateNode *node = &g_array_index (array,
1799 gpointer ddata = node->data;
1800 GDestroyNotify ddestroy = node->destroy;
1803 node->destroy = NULL;
1807 /* defer non-trivial destruction til after we've finished
1808 * iterating, since we must continue to hold the lock */
1809 if (garbage == NULL)
1810 garbage = g_array_new (FALSE, TRUE,
1811 sizeof (GStaticPrivateNode));
1813 g_array_set_size (garbage, garbage->len + 1);
1815 node = &g_array_index (garbage, GStaticPrivateNode,
1818 node->destroy = ddestroy;
1822 UNLOCK_PRIVATE_DATA (thread);
1824 g_thread_free_indices = g_slist_prepend (g_thread_free_indices,
1825 GUINT_TO_POINTER (idx));
1826 G_UNLOCK (g_thread);
1832 for (i = 0; i < garbage->len; i++)
1834 GStaticPrivateNode *node;
1836 node = &g_array_index (garbage, GStaticPrivateNode, i);
1837 node->destroy (node->data);
1840 g_array_free (garbage, TRUE);
1844 /* GThread Extra Functions {{{1 ------------------------------------------- */
1846 g_thread_cleanup (gpointer data)
1850 GRealThread* thread = data;
1853 LOCK_PRIVATE_DATA (thread);
1854 array = thread->private_data;
1855 thread->private_data = NULL;
1856 UNLOCK_PRIVATE_DATA (thread);
1862 for (i = 0; i < array->len; i++ )
1864 GStaticPrivateNode *node =
1865 &g_array_index (array, GStaticPrivateNode, i);
1867 node->destroy (node->data);
1869 g_array_free (array, TRUE);
1872 /* We only free the thread structure, if it isn't joinable. If
1873 it is, the structure is freed in g_thread_join */
1874 if (!thread->thread.joinable)
1879 for (t = g_thread_all_threads, p = NULL; t; p = t, t = t->next)
1886 g_thread_all_threads = t->next;
1890 G_UNLOCK (g_thread);
1892 /* Just to make sure, this isn't used any more */
1893 g_system_thread_assign (thread->system_thread, zero_thread);
1900 g_thread_fail (void)
1902 g_error ("The thread system is not yet initialized.");
1905 #define G_NSEC_PER_SEC 1000000000
1910 return g_get_monotonic_time () * 1000;
1914 g_thread_create_proxy (gpointer data)
1916 GRealThread* thread = data;
1920 /* This has to happen before G_LOCK, as that might call g_thread_self */
1921 g_private_set (&g_thread_specific_private, data);
1923 /* the lock makes sure, that thread->system_thread is written,
1924 before thread->thread.func is called. See g_thread_create. */
1926 G_UNLOCK (g_thread);
1928 thread->retval = thread->thread.func (thread->thread.data);
1934 * g_thread_create_full:
1935 * @func: a function to execute in the new thread.
1936 * @data: an argument to supply to the new thread.
1937 * @stack_size: a stack size for the new thread.
1938 * @joinable: should this thread be joinable?
1939 * @bound: should this thread be bound to a system thread?
1940 * @priority: a priority for the thread.
1941 * @error: return location for error.
1942 * @Returns: the new #GThread on success.
1944 * This function creates a new thread with the priority @priority. If
1945 * the underlying thread implementation supports it, the thread gets a
1946 * stack size of @stack_size or the default value for the current
1947 * platform, if @stack_size is 0.
1949 * If @joinable is %TRUE, you can wait for this threads termination
1950 * calling g_thread_join(). Otherwise the thread will just disappear
1951 * when it terminates. If @bound is %TRUE, this thread will be
1952 * scheduled in the system scope, otherwise the implementation is free
1953 * to do scheduling in the process scope. The first variant is more
1954 * expensive resource-wise, but generally faster. On some systems (e.g.
1955 * Linux) all threads are bound.
1957 * The new thread executes the function @func with the argument @data.
1958 * If the thread was created successfully, it is returned.
1960 * @error can be %NULL to ignore errors, or non-%NULL to report errors.
1961 * The error is set, if and only if the function returns %NULL.
1963 * <note><para>It is not guaranteed that threads with different priorities
1964 * really behave accordingly. On some systems (e.g. Linux) there are no
1965 * thread priorities. On other systems (e.g. Solaris) there doesn't
1966 * seem to be different scheduling for different priorities. All in all
1967 * try to avoid being dependent on priorities. Use
1968 * %G_THREAD_PRIORITY_NORMAL here as a default.</para></note>
1970 * <note><para>Only use g_thread_create_full() if you really can't use
1971 * g_thread_create() instead. g_thread_create() does not take
1972 * @stack_size, @bound, and @priority as arguments, as they should only
1973 * be used in cases in which it is unavoidable.</para></note>
1976 g_thread_create_full (GThreadFunc func,
1981 GThreadPriority priority,
1984 GRealThread* result;
1985 GError *local_error = NULL;
1986 g_return_val_if_fail (func, NULL);
1987 g_return_val_if_fail (priority >= G_THREAD_PRIORITY_LOW, NULL);
1988 g_return_val_if_fail (priority <= G_THREAD_PRIORITY_URGENT, NULL);
1990 result = g_new0 (GRealThread, 1);
1992 result->thread.joinable = joinable;
1993 result->thread.priority = priority;
1994 result->thread.func = func;
1995 result->thread.data = data;
1996 result->private_data = NULL;
1998 G_THREAD_UF (thread_create, (g_thread_create_proxy, result,
1999 stack_size, joinable, bound, priority,
2000 &result->system_thread, &local_error));
2003 result->next = g_thread_all_threads;
2004 g_thread_all_threads = result;
2006 G_UNLOCK (g_thread);
2010 g_propagate_error (error, local_error);
2015 return (GThread*) result;
2020 * @retval: the return value of this thread.
2022 * Exits the current thread. If another thread is waiting for that
2023 * thread using g_thread_join() and the current thread is joinable, the
2024 * waiting thread will be woken up and get @retval as the return value
2025 * of g_thread_join(). If the current thread is not joinable, @retval
2026 * is ignored. Calling
2030 * g_thread_exit (retval);
2032 * </informalexample>
2034 * is equivalent to returning @retval from the function @func, as given
2035 * to g_thread_create().
2037 * <note><para>Never call g_thread_exit() from within a thread of a
2038 * #GThreadPool, as that will mess up the bookkeeping and lead to funny
2039 * and unwanted results.</para></note>
2042 g_thread_exit (gpointer retval)
2044 GRealThread* real = (GRealThread*) g_thread_self ();
2045 real->retval = retval;
2046 G_THREAD_CF (thread_exit, (void)0, ());
2051 * @thread: a #GThread to be waited for.
2052 * @Returns: the return value of the thread.
2054 * Waits until @thread finishes, i.e. the function @func, as given to
2055 * g_thread_create(), returns or g_thread_exit() is called by @thread.
2056 * All resources of @thread including the #GThread struct are released.
2057 * @thread must have been created with @joinable=%TRUE in
2058 * g_thread_create(). The value returned by @func or given to
2059 * g_thread_exit() by @thread is returned by this function.
2062 g_thread_join (GThread* thread)
2064 GRealThread* real = (GRealThread*) thread;
2068 g_return_val_if_fail (thread, NULL);
2069 g_return_val_if_fail (thread->joinable, NULL);
2070 g_return_val_if_fail (!g_system_thread_equal (real->system_thread,
2071 zero_thread), NULL);
2073 G_THREAD_UF (thread_join, (&real->system_thread));
2075 retval = real->retval;
2078 for (t = g_thread_all_threads, p = NULL; t; p = t, t = t->next)
2080 if (t == (GRealThread*) thread)
2085 g_thread_all_threads = t->next;
2089 G_UNLOCK (g_thread);
2091 /* Just to make sure, this isn't used any more */
2092 thread->joinable = 0;
2093 g_system_thread_assign (real->system_thread, zero_thread);
2095 /* the thread structure for non-joinable threads is freed upon
2096 thread end. We free the memory here. This will leave a loose end,
2097 if a joinable thread is not joined. */
2105 * g_thread_set_priority:
2106 * @thread: a #GThread.
2107 * @priority: a new priority for @thread.
2109 * Changes the priority of @thread to @priority.
2111 * <note><para>It is not guaranteed that threads with different
2112 * priorities really behave accordingly. On some systems (e.g. Linux)
2113 * there are no thread priorities. On other systems (e.g. Solaris) there
2114 * doesn't seem to be different scheduling for different priorities. All
2115 * in all try to avoid being dependent on priorities.</para></note>
2118 g_thread_set_priority (GThread* thread,
2119 GThreadPriority priority)
2121 GRealThread* real = (GRealThread*) thread;
2123 g_return_if_fail (thread);
2124 g_return_if_fail (!g_system_thread_equal (real->system_thread, zero_thread));
2125 g_return_if_fail (priority >= G_THREAD_PRIORITY_LOW);
2126 g_return_if_fail (priority <= G_THREAD_PRIORITY_URGENT);
2128 thread->priority = priority;
2130 G_THREAD_CF (thread_set_priority, (void)0,
2131 (&real->system_thread, priority));
2136 * @Returns: the current thread.
2138 * This functions returns the #GThread corresponding to the calling
2142 g_thread_self (void)
2144 GRealThread* thread = g_private_get (&g_thread_specific_private);
2148 /* If no thread data is available, provide and set one. This
2149 can happen for the main thread and for threads, that are not
2151 thread = g_new0 (GRealThread, 1);
2152 thread->thread.joinable = FALSE; /* This is a save guess */
2153 thread->thread.priority = G_THREAD_PRIORITY_NORMAL; /* This is
2155 thread->thread.func = NULL;
2156 thread->thread.data = NULL;
2157 thread->private_data = NULL;
2159 G_THREAD_UF (thread_self, (&thread->system_thread));
2161 g_private_set (&g_thread_specific_private, thread);
2164 thread->next = g_thread_all_threads;
2165 g_thread_all_threads = thread;
2166 G_UNLOCK (g_thread);
2169 return (GThread*)thread;
2172 /* GStaticRWLock {{{1 ----------------------------------------------------- */
2177 * The #GStaticRWLock struct represents a read-write lock. A read-write
2178 * lock can be used for protecting data that some portions of code only
2179 * read from, while others also write. In such situations it is
2180 * desirable that several readers can read at once, whereas of course
2181 * only one writer may write at a time. Take a look at the following
2185 * <title>An array with access functions</title>
2187 * GStaticRWLock rwlock = G_STATIC_RW_LOCK_INIT;
2191 * my_array_get (guint index)
2193 * gpointer retval = NULL;
2198 * g_static_rw_lock_reader_lock (&rwlock);
2199 * if (index < array->len)
2200 * retval = g_ptr_array_index (array, index);
2201 * g_static_rw_lock_reader_unlock (&rwlock);
2207 * my_array_set (guint index, gpointer data)
2209 * g_static_rw_lock_writer_lock (&rwlock);
2212 * array = g_ptr_array_new (<!-- -->);
2214 * if (index >= array->len)
2215 * g_ptr_array_set_size (array, index+1);
2216 * g_ptr_array_index (array, index) = data;
2218 * g_static_rw_lock_writer_unlock (&rwlock);
2223 * This example shows an array which can be accessed by many readers
2224 * (the <function>my_array_get()</function> function) simultaneously,
2225 * whereas the writers (the <function>my_array_set()</function>
2226 * function) will only be allowed once at a time and only if no readers
2227 * currently access the array. This is because of the potentially
2228 * dangerous resizing of the array. Using these functions is fully
2229 * multi-thread safe now.
2231 * Most of the time, writers should have precedence over readers. That
2232 * means, for this implementation, that as soon as a writer wants to
2233 * lock the data, no other reader is allowed to lock the data, whereas,
2234 * of course, the readers that already have locked the data are allowed
2235 * to finish their operation. As soon as the last reader unlocks the
2236 * data, the writer will lock it.
2238 * Even though #GStaticRWLock is not opaque, it should only be used
2239 * with the following functions.
2241 * All of the <function>g_static_rw_lock_*</function> functions can be
2242 * used even if g_thread_init() has not been called. Then they do
2243 * nothing, apart from <function>g_static_rw_lock_*_trylock</function>,
2244 * which does nothing but returning %TRUE.
2246 * <note><para>A read-write lock has a higher overhead than a mutex. For
2247 * example, both g_static_rw_lock_reader_lock() and
2248 * g_static_rw_lock_reader_unlock() have to lock and unlock a
2249 * #GStaticMutex, so it takes at least twice the time to lock and unlock
2250 * a #GStaticRWLock that it does to lock and unlock a #GStaticMutex. So
2251 * only data structures that are accessed by multiple readers, and which
2252 * keep the lock for a considerable time justify a #GStaticRWLock. The
2253 * above example most probably would fare better with a
2254 * #GStaticMutex.</para></note>
2258 * G_STATIC_RW_LOCK_INIT:
2260 * A #GStaticRWLock must be initialized with this macro before it can
2261 * be used. This macro can used be to initialize a variable, but it
2262 * cannot be assigned to a variable. In that case you have to use
2263 * g_static_rw_lock_init().
2267 * GStaticRWLock my_lock = G_STATIC_RW_LOCK_INIT;
2269 * </informalexample>
2273 * g_static_rw_lock_init:
2274 * @lock: a #GStaticRWLock to be initialized.
2276 * A #GStaticRWLock must be initialized with this function before it
2277 * can be used. Alternatively you can initialize it with
2278 * #G_STATIC_RW_LOCK_INIT.
2281 g_static_rw_lock_init (GStaticRWLock* lock)
2283 static const GStaticRWLock init_lock = G_STATIC_RW_LOCK_INIT;
2285 g_return_if_fail (lock);
2291 g_static_rw_lock_wait (GCond** cond, GStaticMutex* mutex)
2294 *cond = g_cond_new ();
2295 g_cond_wait (*cond, g_static_mutex_get_mutex (mutex));
2299 g_static_rw_lock_signal (GStaticRWLock* lock)
2301 if (lock->want_to_write && lock->write_cond)
2302 g_cond_signal (lock->write_cond);
2303 else if (lock->want_to_read && lock->read_cond)
2304 g_cond_broadcast (lock->read_cond);
2308 * g_static_rw_lock_reader_lock:
2309 * @lock: a #GStaticRWLock to lock for reading.
2311 * Locks @lock for reading. There may be unlimited concurrent locks for
2312 * reading of a #GStaticRWLock at the same time. If @lock is already
2313 * locked for writing by another thread or if another thread is already
2314 * waiting to lock @lock for writing, this function will block until
2315 * @lock is unlocked by the other writing thread and no other writing
2316 * threads want to lock @lock. This lock has to be unlocked by
2317 * g_static_rw_lock_reader_unlock().
2319 * #GStaticRWLock is not recursive. It might seem to be possible to
2320 * recursively lock for reading, but that can result in a deadlock, due
2321 * to writer preference.
2324 g_static_rw_lock_reader_lock (GStaticRWLock* lock)
2326 g_return_if_fail (lock);
2328 if (!g_threads_got_initialized)
2331 g_static_mutex_lock (&lock->mutex);
2332 lock->want_to_read++;
2333 while (lock->have_writer || lock->want_to_write)
2334 g_static_rw_lock_wait (&lock->read_cond, &lock->mutex);
2335 lock->want_to_read--;
2336 lock->read_counter++;
2337 g_static_mutex_unlock (&lock->mutex);
2341 * g_static_rw_lock_reader_trylock:
2342 * @lock: a #GStaticRWLock to lock for reading.
2343 * @Returns: %TRUE, if @lock could be locked for reading.
2345 * Tries to lock @lock for reading. If @lock is already locked for
2346 * writing by another thread or if another thread is already waiting to
2347 * lock @lock for writing, immediately returns %FALSE. Otherwise locks
2348 * @lock for reading and returns %TRUE. This lock has to be unlocked by
2349 * g_static_rw_lock_reader_unlock().
2352 g_static_rw_lock_reader_trylock (GStaticRWLock* lock)
2354 gboolean ret_val = FALSE;
2356 g_return_val_if_fail (lock, FALSE);
2358 if (!g_threads_got_initialized)
2361 g_static_mutex_lock (&lock->mutex);
2362 if (!lock->have_writer && !lock->want_to_write)
2364 lock->read_counter++;
2367 g_static_mutex_unlock (&lock->mutex);
2372 * g_static_rw_lock_reader_unlock:
2373 * @lock: a #GStaticRWLock to unlock after reading.
2375 * Unlocks @lock. If a thread waits to lock @lock for writing and all
2376 * locks for reading have been unlocked, the waiting thread is woken up
2377 * and can lock @lock for writing.
2380 g_static_rw_lock_reader_unlock (GStaticRWLock* lock)
2382 g_return_if_fail (lock);
2384 if (!g_threads_got_initialized)
2387 g_static_mutex_lock (&lock->mutex);
2388 lock->read_counter--;
2389 if (lock->read_counter == 0)
2390 g_static_rw_lock_signal (lock);
2391 g_static_mutex_unlock (&lock->mutex);
2395 * g_static_rw_lock_writer_lock:
2396 * @lock: a #GStaticRWLock to lock for writing.
2398 * Locks @lock for writing. If @lock is already locked for writing or
2399 * reading by other threads, this function will block until @lock is
2400 * completely unlocked and then lock @lock for writing. While this
2401 * functions waits to lock @lock, no other thread can lock @lock for
2402 * reading. When @lock is locked for writing, no other thread can lock
2403 * @lock (neither for reading nor writing). This lock has to be
2404 * unlocked by g_static_rw_lock_writer_unlock().
2407 g_static_rw_lock_writer_lock (GStaticRWLock* lock)
2409 g_return_if_fail (lock);
2411 if (!g_threads_got_initialized)
2414 g_static_mutex_lock (&lock->mutex);
2415 lock->want_to_write++;
2416 while (lock->have_writer || lock->read_counter)
2417 g_static_rw_lock_wait (&lock->write_cond, &lock->mutex);
2418 lock->want_to_write--;
2419 lock->have_writer = TRUE;
2420 g_static_mutex_unlock (&lock->mutex);
2424 * g_static_rw_lock_writer_trylock:
2425 * @lock: a #GStaticRWLock to lock for writing.
2426 * @Returns: %TRUE, if @lock could be locked for writing.
2428 * Tries to lock @lock for writing. If @lock is already locked (for
2429 * either reading or writing) by another thread, it immediately returns
2430 * %FALSE. Otherwise it locks @lock for writing and returns %TRUE. This
2431 * lock has to be unlocked by g_static_rw_lock_writer_unlock().
2434 g_static_rw_lock_writer_trylock (GStaticRWLock* lock)
2436 gboolean ret_val = FALSE;
2438 g_return_val_if_fail (lock, FALSE);
2440 if (!g_threads_got_initialized)
2443 g_static_mutex_lock (&lock->mutex);
2444 if (!lock->have_writer && !lock->read_counter)
2446 lock->have_writer = TRUE;
2449 g_static_mutex_unlock (&lock->mutex);
2454 * g_static_rw_lock_writer_unlock:
2455 * @lock: a #GStaticRWLock to unlock after writing.
2457 * Unlocks @lock. If a thread is waiting to lock @lock for writing and
2458 * all locks for reading have been unlocked, the waiting thread is
2459 * woken up and can lock @lock for writing. If no thread is waiting to
2460 * lock @lock for writing, and some thread or threads are waiting to
2461 * lock @lock for reading, the waiting threads are woken up and can
2462 * lock @lock for reading.
2465 g_static_rw_lock_writer_unlock (GStaticRWLock* lock)
2467 g_return_if_fail (lock);
2469 if (!g_threads_got_initialized)
2472 g_static_mutex_lock (&lock->mutex);
2473 lock->have_writer = FALSE;
2474 g_static_rw_lock_signal (lock);
2475 g_static_mutex_unlock (&lock->mutex);
2479 * g_static_rw_lock_free:
2480 * @lock: a #GStaticRWLock to be freed.
2482 * Releases all resources allocated to @lock.
2484 * You don't have to call this functions for a #GStaticRWLock with an
2485 * unbounded lifetime, i.e. objects declared 'static', but if you have
2486 * a #GStaticRWLock as a member of a structure, and the structure is
2487 * freed, you should also free the #GStaticRWLock.
2490 g_static_rw_lock_free (GStaticRWLock* lock)
2492 g_return_if_fail (lock);
2494 if (lock->read_cond)
2496 g_cond_free (lock->read_cond);
2497 lock->read_cond = NULL;
2499 if (lock->write_cond)
2501 g_cond_free (lock->write_cond);
2502 lock->write_cond = NULL;
2504 g_static_mutex_free (&lock->mutex);
2507 /* Unsorted {{{1 ---------------------------------------------------------- */
2511 * @thread_func: function to call for all GThread structures
2512 * @user_data: second argument to @thread_func
2514 * Call @thread_func on all existing #GThread structures. Note that
2515 * threads may decide to exit while @thread_func is running, so
2516 * without intimate knowledge about the lifetime of foreign threads,
2517 * @thread_func shouldn't access the GThread* pointer passed in as
2518 * first argument. However, @thread_func will not be called for threads
2519 * which are known to have exited already.
2521 * Due to thread lifetime checks, this function has an execution complexity
2522 * which is quadratic in the number of existing threads.
2527 g_thread_foreach (GFunc thread_func,
2530 GSList *slist = NULL;
2531 GRealThread *thread;
2532 g_return_if_fail (thread_func != NULL);
2533 /* snapshot the list of threads for iteration */
2535 for (thread = g_thread_all_threads; thread; thread = thread->next)
2536 slist = g_slist_prepend (slist, thread);
2537 G_UNLOCK (g_thread);
2538 /* walk the list, skipping non-existent threads */
2541 GSList *node = slist;
2543 /* check whether the current thread still exists */
2545 for (thread = g_thread_all_threads; thread; thread = thread->next)
2546 if (thread == node->data)
2548 G_UNLOCK (g_thread);
2550 thread_func (thread, user_data);
2551 g_slist_free_1 (node);
2556 * g_thread_get_initialized
2558 * Indicates if g_thread_init() has been called.
2560 * Returns: %TRUE if threads have been initialized.
2565 g_thread_get_initialized ()
2567 return g_thread_supported ();
2575 mutex = g_slice_new (GMutex);
2576 g_mutex_init (mutex);
2582 g_mutex_free (GMutex *mutex)
2584 g_mutex_clear (mutex);
2585 g_slice_free (GMutex, mutex);
2593 cond = g_slice_new (GCond);
2600 g_cond_free (GCond *cond)
2602 g_cond_clear (cond);
2603 g_slice_free (GCond, cond);