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 */
60 #include "gtestutils.h"
65 * @short_description: portable support for threads, mutexes, locks,
66 * conditions and thread private data
67 * @see_also: #GThreadPool, #GAsyncQueue
69 * Threads act almost like processes, but unlike processes all threads
70 * of one process share the same memory. This is good, as it provides
71 * easy communication between the involved threads via this shared
72 * memory, and it is bad, because strange things (so called
73 * "Heisenbugs") might happen if the program is not carefully designed.
74 * In particular, due to the concurrent nature of threads, no
75 * assumptions on the order of execution of code running in different
76 * threads can be made, unless order is explicitly forced by the
77 * programmer through synchronization primitives.
79 * The aim of the thread-related functions in GLib is to provide a
80 * portable means for writing multi-threaded software. There are
81 * primitives for mutexes to protect the access to portions of memory
82 * (#GMutex, #GRecMutex and #GRWLock). There is a facility to use
83 * individual bits for locks (g_bit_lock()). There are primitives
84 * for condition variables to allow synchronization of threads (#GCond).
85 * There are primitives for thread-private data - data that every
86 * thread has a private instance of (#GPrivate). There are facilities
87 * for one-time initialization (#GOnce, g_once_init_enter()). Finally,
88 * there are primitives to create and manage threads (#GThread).
90 * The GLib threading system used to be initialized with g_thread_init().
91 * This is no longer necessary. Since version 2.32, the GLib threading
92 * system is automatically initialized at the start of your program,
93 * and all thread-creation functions and synchronization primitives
94 * are available right away.
96 * Note that it is not safe to assume that your program has no threads
97 * even if you don't call g_thread_new() yourself. GLib and GIO can
98 * and will create threads for their own purposes in some cases, such
99 * as when using g_unix_signal_source_new() or when using #GDBus.
101 * Originally, UNIX did not have threads, and therefore some traditional
102 * UNIX APIs are problematic in threaded programs. Some notable examples
106 * C library functions that return data in statically allocated
107 * buffers, such as strtok() or strerror(). For many of these,
108 * there are thread-safe variants with a _r suffix, or you can
109 * look at corresponding GLib APIs (like g_strsplit() or g_strerror()).
112 * setenv() and unsetenv() manipulate the process environment in
113 * a not thread-safe way, and may interfere with getenv() calls
114 * in other threads. Note that getenv() calls may be
115 * <quote>hidden</quote> behind other APIs. For example, GNU gettext()
116 * calls getenv() under the covers. In general, it is best to treat
117 * the environment as readonly. If you absolutely have to modify the
118 * environment, do it early in main(), when no other threads are around yet.
121 * setlocale() changes the locale for the entire process, affecting
122 * all threads. Temporary changes to the locale are often made to
123 * change the behavior of string scanning or formatting functions
124 * like scanf() or printf(). GLib offers a number of string APIs
125 * (like g_ascii_formatd() or g_ascii_strtod()) that can often be
126 * used as an alternative. Or you can use the uselocale() function
127 * to change the locale only for the current thread.
131 * GLib itself is internally completely thread-safe (all global data is
132 * automatically locked), but individual data structure instances are
133 * not automatically locked for performance reasons. For example,
134 * you must coordinate accesses to the same #GHashTable from multiple
135 * threads. The two notable exceptions from this rule are #GMainLoop
136 * and #GAsyncQueue, which <emphasis>are</emphasis> thread-safe and
137 * need no further application-level locking to be accessed from
138 * multiple threads. Most refcounting functions such as g_object_ref()
139 * are also thread-safe.
142 /* G_LOCK Documentation {{{1 ---------------------------------------------- */
146 * @name: the name of the lock
148 * The %G_LOCK_* macros provide a convenient interface to #GMutex.
149 * #G_LOCK_DEFINE defines a lock. It can appear in any place where
150 * variable definitions may appear in programs, i.e. in the first block
151 * of a function or outside of functions. The @name parameter will be
152 * mangled to get the name of the #GMutex. This means that you
153 * can use names of existing variables as the parameter - e.g. the name
154 * of the variable you intend to protect with the lock. Look at our
155 * <function>give_me_next_number()</function> example using the
159 * <title>Using the %G_LOCK_* convenience macros</title>
161 * G_LOCK_DEFINE (current_number);
164 * give_me_next_number (void)
166 * static int current_number = 0;
169 * G_LOCK (current_number);
170 * ret_val = current_number = calc_next_number (current_number);
171 * G_UNLOCK (current_number);
180 * G_LOCK_DEFINE_STATIC:
181 * @name: the name of the lock
183 * This works like #G_LOCK_DEFINE, but it creates a static object.
188 * @name: the name of the lock
190 * This declares a lock, that is defined with #G_LOCK_DEFINE in another
196 * @name: the name of the lock
198 * Works like g_mutex_lock(), but for a lock defined with
204 * @name: the name of the lock
205 * @Returns: %TRUE, if the lock could be locked.
207 * Works like g_mutex_trylock(), but for a lock defined with
213 * @name: the name of the lock
215 * Works like g_mutex_unlock(), but for a lock defined with
219 /* GMutex Documentation {{{1 ------------------------------------------ */
224 * The #GMutex struct is an opaque data structure to represent a mutex
225 * (mutual exclusion). It can be used to protect data against shared
226 * access. Take for example the following function:
229 * <title>A function which will not work in a threaded environment</title>
232 * give_me_next_number (void)
234 * static int current_number = 0;
236 * /<!-- -->* now do a very complicated calculation to calculate the new
237 * * number, this might for example be a random number generator
239 * current_number = calc_next_number (current_number);
241 * return current_number;
246 * It is easy to see that this won't work in a multi-threaded
247 * application. There current_number must be protected against shared
248 * access. A #GMutex can be used as a solution to this problem:
251 * <title>Using GMutex to protected a shared variable</title>
254 * give_me_next_number (void)
256 * static GMutex mutex;
257 * static int current_number = 0;
260 * g_mutex_lock (&mutex);
261 * ret_val = current_number = calc_next_number (current_number);
262 * g_mutex_unlock (&mutex);
269 * Notice that the #GMutex is not initialised to any particular value.
270 * Its placement in static storage ensures that it will be initialised
271 * to all-zeros, which is appropriate.
273 * If a #GMutex is placed in other contexts (eg: embedded in a struct)
274 * then it must be explicitly initialised using g_mutex_init().
276 * A #GMutex should only be accessed via <function>g_mutex_</function>
280 /* GRecMutex Documentation {{{1 -------------------------------------- */
285 * The GRecMutex struct is an opaque data structure to represent a
286 * recursive mutex. It is similar to a #GMutex with the difference
287 * that it is possible to lock a GRecMutex multiple times in the same
288 * thread without deadlock. When doing so, care has to be taken to
289 * unlock the recursive mutex as often as it has been locked.
291 * If a #GRecMutex is allocated in static storage then it can be used
292 * without initialisation. Otherwise, you should call
293 * g_rec_mutex_init() on it and g_rec_mutex_clear() when done.
295 * A GRecMutex should only be accessed with the
296 * <function>g_rec_mutex_</function> functions.
301 /* GRWLock Documentation {{{1 ---------------------------------------- */
306 * The GRWLock struct is an opaque data structure to represent a
307 * reader-writer lock. It is similar to a #GMutex in that it allows
308 * multiple threads to coordinate access to a shared resource.
310 * The difference to a mutex is that a reader-writer lock discriminates
311 * between read-only ('reader') and full ('writer') access. While only
312 * one thread at a time is allowed write access (by holding the 'writer'
313 * lock via g_rw_lock_writer_lock()), multiple threads can gain
314 * simultaneous read-only access (by holding the 'reader' lock via
315 * g_rw_lock_reader_lock()).
318 * <title>An array with access functions</title>
324 * my_array_get (guint index)
326 * gpointer retval = NULL;
331 * g_rw_lock_reader_lock (&lock);
332 * if (index < array->len)
333 * retval = g_ptr_array_index (array, index);
334 * g_rw_lock_reader_unlock (&lock);
340 * my_array_set (guint index, gpointer data)
342 * g_rw_lock_writer_lock (&lock);
345 * array = g_ptr_array_new (<!-- -->);
347 * if (index >= array->len)
348 * g_ptr_array_set_size (array, index+1);
349 * g_ptr_array_index (array, index) = data;
351 * g_rw_lock_writer_unlock (&lock);
355 * This example shows an array which can be accessed by many readers
356 * (the <function>my_array_get()</function> function) simultaneously,
357 * whereas the writers (the <function>my_array_set()</function>
358 * function) will only be allowed once at a time and only if no readers
359 * currently access the array. This is because of the potentially
360 * dangerous resizing of the array. Using these functions is fully
361 * multi-thread safe now.
365 * If a #GRWLock is allocated in static storage then it can be used
366 * without initialisation. Otherwise, you should call
367 * g_rw_lock_init() on it and g_rw_lock_clear() when done.
369 * A GRWLock should only be accessed with the
370 * <function>g_rw_lock_</function> functions.
375 /* GCond Documentation {{{1 ------------------------------------------ */
380 * The #GCond struct is an opaque data structure that represents a
381 * condition. Threads can block on a #GCond if they find a certain
382 * condition to be false. If other threads change the state of this
383 * condition they signal the #GCond, and that causes the waiting
384 * threads to be woken up.
386 * Consider the following example of a shared variable. One or more
387 * threads can wait for data to be published to the variable and when
388 * another thread publishes the data, it can signal one of the waiting
389 * threads to wake up to collect the data.
393 * Using GCond to block a thread until a condition is satisfied
396 * gpointer current_data = NULL;
401 * push_data (gpointer data)
403 * g_mutex_lock (&data_mutex);
404 * current_data = data;
405 * g_cond_signal (&data_cond);
406 * g_mutex_unlock (&data_mutex);
414 * g_mutex_lock (&data_mutex);
415 * while (!current_data)
416 * g_cond_wait (&data_cond, &data_mutex);
417 * data = current_data;
418 * current_data = NULL;
419 * g_mutex_unlock (&data_mutex);
426 * Whenever a thread calls pop_data() now, it will wait until
427 * current_data is non-%NULL, i.e. until some other thread
428 * has called push_data().
430 * The example shows that use of a condition variable must always be
431 * paired with a mutex. Without the use of a mutex, there would be a
432 * race between the check of <varname>current_data</varname> by the
433 * while loop in <function>pop_data</function> and waiting.
434 * Specifically, another thread could set <varname>pop_data</varname>
435 * after the check, and signal the cond (with nobody waiting on it)
436 * before the first thread goes to sleep. #GCond is specifically useful
437 * for its ability to release the mutex and go to sleep atomically.
439 * It is also important to use the g_cond_wait() and g_cond_wait_until()
440 * functions only inside a loop which checks for the condition to be
441 * true. See g_cond_wait() for an explanation of why the condition may
442 * not be true even after it returns.
444 * If a #GCond is allocated in static storage then it can be used
445 * without initialisation. Otherwise, you should call g_cond_init() on
446 * it and g_cond_clear() when done.
448 * A #GCond should only be accessed via the <function>g_cond_</function>
452 /* GThread Documentation {{{1 ---------------------------------------- */
457 * The #GThread struct represents a running thread. This struct
458 * is returned by g_thread_new() or g_thread_try_new(). You can
459 * obtain the #GThread struct representing the current thead by
460 * calling g_thread_self().
462 * GThread is refcounted, see g_thread_ref() and g_thread_unref().
463 * The thread represented by it holds a reference while it is running,
464 * and g_thread_join() consumes the reference that it is given, so
465 * it is normally not necessary to manage GThread references
468 * The structure is opaque -- none of its fields may be directly
474 * @data: data passed to the thread
476 * Specifies the type of the @func functions passed to g_thread_new()
477 * or g_thread_try_new().
479 * Returns: the return value of the thread
483 * g_thread_supported:
485 * This macro returns %TRUE if the thread system is initialized,
486 * and %FALSE if it is not.
488 * For language bindings, g_thread_get_initialized() provides
489 * the same functionality as a function.
491 * Returns: %TRUE, if the thread system is initialized
494 /* GThreadError {{{1 ------------------------------------------------------- */
497 * @G_THREAD_ERROR_AGAIN: a thread couldn't be created due to resource
498 * shortage. Try again later.
500 * Possible errors of thread related functions.
506 * The error domain of the GLib thread subsystem.
509 g_thread_error_quark (void)
511 return g_quark_from_static_string ("g_thread_error");
514 /* Local Data {{{1 -------------------------------------------------------- */
516 static GMutex g_once_mutex;
517 static GCond g_once_cond;
518 static GSList *g_once_init_list = NULL;
520 static void g_thread_cleanup (gpointer data);
521 static GPrivate g_thread_specific_private = G_PRIVATE_INIT (g_thread_cleanup);
523 G_LOCK_DEFINE_STATIC (g_thread_new);
525 /* GOnce {{{1 ------------------------------------------------------------- */
529 * @status: the status of the #GOnce
530 * @retval: the value returned by the call to the function, if @status
531 * is %G_ONCE_STATUS_READY
533 * A #GOnce struct controls a one-time initialization function. Any
534 * one-time initialization function must have its own unique #GOnce
543 * A #GOnce must be initialized with this macro before it can be used.
546 * GOnce my_once = G_ONCE_INIT;
554 * @G_ONCE_STATUS_NOTCALLED: the function has not been called yet.
555 * @G_ONCE_STATUS_PROGRESS: the function call is currently in progress.
556 * @G_ONCE_STATUS_READY: the function has been called.
558 * The possible statuses of a one-time initialization function
559 * controlled by a #GOnce struct.
566 * @once: a #GOnce structure
567 * @func: the #GThreadFunc function associated to @once. This function
568 * is called only once, regardless of the number of times it and
569 * its associated #GOnce struct are passed to g_once().
570 * @arg: data to be passed to @func
572 * The first call to this routine by a process with a given #GOnce
573 * struct calls @func with the given argument. Thereafter, subsequent
574 * calls to g_once() with the same #GOnce struct do not call @func
575 * again, but return the stored result of the first call. On return
576 * from g_once(), the status of @once will be %G_ONCE_STATUS_READY.
578 * For example, a mutex or a thread-specific data key must be created
579 * exactly once. In a threaded environment, calling g_once() ensures
580 * that the initialization is serialized across multiple threads.
582 * Calling g_once() recursively on the same #GOnce struct in
583 * @func will lead to a deadlock.
587 * get_debug_flags (void)
589 * static GOnce my_once = G_ONCE_INIT;
591 * g_once (&my_once, parse_debug_flags, NULL);
593 * return my_once.retval;
600 g_once_impl (GOnce *once,
604 g_mutex_lock (&g_once_mutex);
606 while (once->status == G_ONCE_STATUS_PROGRESS)
607 g_cond_wait (&g_once_cond, &g_once_mutex);
609 if (once->status != G_ONCE_STATUS_READY)
611 once->status = G_ONCE_STATUS_PROGRESS;
612 g_mutex_unlock (&g_once_mutex);
614 once->retval = func (arg);
616 g_mutex_lock (&g_once_mutex);
617 once->status = G_ONCE_STATUS_READY;
618 g_cond_broadcast (&g_once_cond);
621 g_mutex_unlock (&g_once_mutex);
628 * @value_location: location of a static initializable variable
631 * Function to be called when starting a critical initialization
632 * section. The argument @value_location must point to a static
633 * 0-initialized variable that will be set to a value other than 0 at
634 * the end of the initialization section. In combination with
635 * g_once_init_leave() and the unique address @value_location, it can
636 * be ensured that an initialization section will be executed only once
637 * during a program's life time, and that concurrent threads are
638 * blocked until initialization completed. To be used in constructs
642 * static gsize initialization_value = 0;
644 * if (g_once_init_enter (&initialization_value))
646 * gsize setup_value = 42; /** initialization code here **/
648 * g_once_init_leave (&initialization_value, setup_value);
651 * /** use initialization_value here **/
654 * Returns: %TRUE if the initialization section should be entered,
655 * %FALSE and blocks otherwise
660 (g_once_init_enter) (volatile void *pointer)
662 volatile gsize *value_location = pointer;
663 gboolean need_init = FALSE;
664 g_mutex_lock (&g_once_mutex);
665 if (g_atomic_pointer_get (value_location) == NULL)
667 if (!g_slist_find (g_once_init_list, (void*) value_location))
670 g_once_init_list = g_slist_prepend (g_once_init_list, (void*) value_location);
674 g_cond_wait (&g_once_cond, &g_once_mutex);
675 while (g_slist_find (g_once_init_list, (void*) value_location));
677 g_mutex_unlock (&g_once_mutex);
683 * @value_location: location of a static initializable variable
685 * @result: new non-0 value for *@value_location
687 * Counterpart to g_once_init_enter(). Expects a location of a static
688 * 0-initialized initialization variable, and an initialization value
689 * other than 0. Sets the variable to the initialization value, and
690 * releases concurrent threads blocking in g_once_init_enter() on this
691 * initialization variable.
696 (g_once_init_leave) (volatile void *pointer,
699 volatile gsize *value_location = pointer;
701 g_return_if_fail (g_atomic_pointer_get (value_location) == NULL);
702 g_return_if_fail (result != 0);
703 g_return_if_fail (g_once_init_list != NULL);
705 g_atomic_pointer_set (value_location, result);
706 g_mutex_lock (&g_once_mutex);
707 g_once_init_list = g_slist_remove (g_once_init_list, (void*) value_location);
708 g_cond_broadcast (&g_once_cond);
709 g_mutex_unlock (&g_once_mutex);
712 /* GThread {{{1 -------------------------------------------------------- */
716 * @thread: a #GThread
718 * Increase the reference count on @thread.
720 * Returns: a new reference to @thread
725 g_thread_ref (GThread *thread)
727 GRealThread *real = (GRealThread *) thread;
729 g_atomic_int_inc (&real->ref_count);
736 * @thread: a #GThread
738 * Decrease the reference count on @thread, possibly freeing all
739 * resources associated with it.
741 * Note that each thread holds a reference to its #GThread while
742 * it is running, so it is safe to drop your own reference to it
743 * if you don't need it anymore.
748 g_thread_unref (GThread *thread)
750 GRealThread *real = (GRealThread *) thread;
752 if (g_atomic_int_dec_and_test (&real->ref_count))
755 g_system_thread_free (real);
757 g_slice_free (GRealThread, real);
762 g_thread_cleanup (gpointer data)
764 g_thread_unref (data);
768 g_thread_proxy (gpointer data)
770 GRealThread* thread = data;
775 g_system_thread_set_name (thread->name);
777 /* This has to happen before G_LOCK, as that might call g_thread_self */
778 g_private_set (&g_thread_specific_private, data);
780 /* The lock makes sure that g_thread_new_internal() has a chance to
781 * setup 'func' and 'data' before we make the call.
783 G_LOCK (g_thread_new);
784 G_UNLOCK (g_thread_new);
786 thread->retval = thread->thread.func (thread->thread.data);
793 * @name: a name for the new thread
794 * @func: a function to execute in the new thread
795 * @data: an argument to supply to the new thread
797 * This function creates a new thread. The new thread starts by invoking
798 * @func with the argument data. The thread will run until @func returns
799 * or until g_thread_exit() is called from the new thread. The return value
800 * of @func becomes the return value of the thread, which can be obtained
801 * with g_thread_join().
803 * The @name can be useful for discriminating threads in a debugger.
804 * Some systems restrict the length of @name to 16 bytes.
806 * If the thread can not be created the program aborts. See
807 * g_thread_try_new() if you want to attempt to deal with failures.
809 * To free the struct returned by this function, use g_thread_unref().
810 * Note that g_thread_join() implicitly unrefs the #GThread as well.
812 * Returns: the new #GThread
817 g_thread_new (const gchar *name,
821 GError *error = NULL;
824 thread = g_thread_new_internal (name, g_thread_proxy, func, data, 0, &error);
826 if G_UNLIKELY (thread == NULL)
827 g_error ("creating thread '%s': %s", name ? name : "", error->message);
834 * @name: a name for the new thread
835 * @func: a function to execute in the new thread
836 * @data: an argument to supply to the new thread
837 * @error: return location for error, or %NULL
839 * This function is the same as g_thread_new() except that
840 * it allows for the possibility of failure.
842 * If a thread can not be created (due to resource limits),
843 * @error is set and %NULL is returned.
845 * Returns: the new #GThread, or %NULL if an error occurred
850 g_thread_try_new (const gchar *name,
855 return g_thread_new_internal (name, g_thread_proxy, func, data, 0, error);
859 g_thread_new_internal (const gchar *name,
868 g_return_val_if_fail (func != NULL, NULL);
870 G_LOCK (g_thread_new);
871 thread = g_system_thread_new (proxy, stack_size, error);
874 thread->ref_count = 2;
876 thread->thread.joinable = TRUE;
877 thread->thread.func = func;
878 thread->thread.data = data;
881 G_UNLOCK (g_thread_new);
883 return (GThread*) thread;
888 * @retval: the return value of this thread
890 * Terminates the current thread.
892 * If another thread is waiting for us using g_thread_join() then the
893 * waiting thread will be woken up and get @retval as the return value
894 * of g_thread_join().
896 * Calling <literal>g_thread_exit (retval)</literal> is equivalent to
897 * returning @retval from the function @func, as given to g_thread_new().
900 * You must only call g_thread_exit() from a thread that you created
901 * yourself with g_thread_new() or related APIs. You must not call
902 * this function from a thread created with another threading library
903 * or or from within a #GThreadPool.
907 g_thread_exit (gpointer retval)
909 GRealThread* real = (GRealThread*) g_thread_self ();
911 if G_UNLIKELY (!real->ours)
912 g_error ("attempt to g_thread_exit() a thread not created by GLib");
914 real->retval = retval;
916 g_system_thread_exit ();
921 * @thread: a #GThread
923 * Waits until @thread finishes, i.e. the function @func, as
924 * given to g_thread_new(), returns or g_thread_exit() is called.
925 * If @thread has already terminated, then g_thread_join()
926 * returns immediately.
928 * Any thread can wait for any other thread by calling g_thread_join(),
929 * not just its 'creator'. Calling g_thread_join() from multiple threads
930 * for the same @thread leads to undefined behaviour.
932 * The value returned by @func or given to g_thread_exit() is
933 * returned by this function.
935 * g_thread_join() consumes the reference to the passed-in @thread.
936 * This will usually cause the #GThread struct and associated resources
937 * to be freed. Use g_thread_ref() to obtain an extra reference if you
938 * want to keep the GThread alive beyond the g_thread_join() call.
940 * Returns: the return value of the thread
943 g_thread_join (GThread *thread)
945 GRealThread *real = (GRealThread*) thread;
948 g_return_val_if_fail (thread, NULL);
949 g_return_val_if_fail (real->ours, NULL);
951 g_system_thread_wait (real);
953 retval = real->retval;
955 /* Just to make sure, this isn't used any more */
956 thread->joinable = 0;
958 g_thread_unref (thread);
966 * This functions returns the #GThread corresponding to the
967 * current thread. Note that this function does not increase
968 * the reference count of the returned struct.
970 * This function will return a #GThread even for threads that
971 * were not created by GLib (i.e. those created by other threading
972 * APIs). This may be useful for thread identification purposes
973 * (i.e. comparisons) but you must not use GLib functions (such
974 * as g_thread_join()) on these threads.
976 * Returns: the #GThread representing the current thread
981 GRealThread* thread = g_private_get (&g_thread_specific_private);
985 /* If no thread data is available, provide and set one.
986 * This can happen for the main thread and for threads
987 * that are not created by GLib.
989 thread = g_slice_new0 (GRealThread);
990 thread->ref_count = 1;
992 g_private_set (&g_thread_specific_private, thread);
995 return (GThread*) thread;
999 /* vim: set foldmethod=marker: */