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, see <http://www.gnu.org/licenses/>.
22 /* Prelude {{{1 ----------------------------------------------------------- */
25 * Modified by the GLib Team and others 1997-2000. See the AUTHORS
26 * file for a list of people on the GLib Team. See the ChangeLog
27 * files for a list of changes. These files are distributed with
28 * GLib at ftp://ftp.gtk.org/pub/gtk/.
35 /* implement gthread.h's inline functions */
36 #define G_IMPLEMENT_INLINES 1
37 #define __G_THREAD_C__
42 #include "gthreadprivate.h"
55 #endif /* G_OS_WIN32 */
58 #include "gstrfuncs.h"
59 #include "gtestutils.h"
64 * @short_description: portable support for threads, mutexes, locks,
65 * conditions and thread private data
66 * @see_also: #GThreadPool, #GAsyncQueue
68 * Threads act almost like processes, but unlike processes all threads
69 * of one process share the same memory. This is good, as it provides
70 * easy communication between the involved threads via this shared
71 * memory, and it is bad, because strange things (so called
72 * "Heisenbugs") might happen if the program is not carefully designed.
73 * In particular, due to the concurrent nature of threads, no
74 * assumptions on the order of execution of code running in different
75 * threads can be made, unless order is explicitly forced by the
76 * programmer through synchronization primitives.
78 * The aim of the thread-related functions in GLib is to provide a
79 * portable means for writing multi-threaded software. There are
80 * primitives for mutexes to protect the access to portions of memory
81 * (#GMutex, #GRecMutex and #GRWLock). There is a facility to use
82 * individual bits for locks (g_bit_lock()). There are primitives
83 * for condition variables to allow synchronization of threads (#GCond).
84 * There are primitives for thread-private data - data that every
85 * thread has a private instance of (#GPrivate). There are facilities
86 * for one-time initialization (#GOnce, g_once_init_enter()). Finally,
87 * there are primitives to create and manage threads (#GThread).
89 * The GLib threading system used to be initialized with g_thread_init().
90 * This is no longer necessary. Since version 2.32, the GLib threading
91 * system is automatically initialized at the start of your program,
92 * and all thread-creation functions and synchronization primitives
93 * are available right away.
95 * Note that it is not safe to assume that your program has no threads
96 * even if you don't call g_thread_new() yourself. GLib and GIO can
97 * and will create threads for their own purposes in some cases, such
98 * as when using g_unix_signal_source_new() or when using GDBus.
100 * Originally, UNIX did not have threads, and therefore some traditional
101 * UNIX APIs are problematic in threaded programs. Some notable examples
105 * C library functions that return data in statically allocated
106 * buffers, such as strtok() or strerror(). For many of these,
107 * there are thread-safe variants with a _r suffix, or you can
108 * look at corresponding GLib APIs (like g_strsplit() or g_strerror()).
111 * setenv() and unsetenv() manipulate the process environment in
112 * a not thread-safe way, and may interfere with getenv() calls
113 * in other threads. Note that getenv() calls may be
114 * <quote>hidden</quote> behind other APIs. For example, GNU gettext()
115 * calls getenv() under the covers. In general, it is best to treat
116 * the environment as readonly. If you absolutely have to modify the
117 * environment, do it early in main(), when no other threads are around yet.
120 * setlocale() changes the locale for the entire process, affecting
121 * all threads. Temporary changes to the locale are often made to
122 * change the behavior of string scanning or formatting functions
123 * like scanf() or printf(). GLib offers a number of string APIs
124 * (like g_ascii_formatd() or g_ascii_strtod()) that can often be
125 * used as an alternative. Or you can use the uselocale() function
126 * to change the locale only for the current thread.
129 * fork() only takes the calling thread into the child's copy of the
130 * process image. If other threads were executing in critical
131 * sections they could have left mutexes locked which could easily
132 * cause deadlocks in the new child. For this reason, you should
133 * call exit() or exec() as soon as possible in the child and only
134 * make signal-safe library calls before that.
137 * daemon() uses fork() in a way contrary to what is described
138 * above. It should not be used with GLib programs.
142 * GLib itself is internally completely thread-safe (all global data is
143 * automatically locked), but individual data structure instances are
144 * not automatically locked for performance reasons. For example,
145 * you must coordinate accesses to the same #GHashTable from multiple
146 * threads. The two notable exceptions from this rule are #GMainLoop
147 * and #GAsyncQueue, which are thread-safe and need no further
148 * application-level locking to be accessed from multiple threads.
149 * Most refcounting functions such as g_object_ref() are also thread-safe.
152 /* G_LOCK Documentation {{{1 ---------------------------------------------- */
156 * @name: the name of the lock
158 * The <literal>G_LOCK_*</literal> macros provide a convenient interface to #GMutex.
159 * #G_LOCK_DEFINE defines a lock. It can appear in any place where
160 * variable definitions may appear in programs, i.e. in the first block
161 * of a function or outside of functions. The @name parameter will be
162 * mangled to get the name of the #GMutex. This means that you
163 * can use names of existing variables as the parameter - e.g. the name
164 * of the variable you intend to protect with the lock. Look at our
165 * <function>give_me_next_number()</function> example using the
166 * <literal>G_LOCK_*</literal> macros:
169 * <title>Using the <literal>G_LOCK_*</literal> convenience macros</title>
171 * G_LOCK_DEFINE (current_number);
174 * give_me_next_number (void)
176 * static int current_number = 0;
179 * G_LOCK (current_number);
180 * ret_val = current_number = calc_next_number (current_number);
181 * G_UNLOCK (current_number);
190 * G_LOCK_DEFINE_STATIC:
191 * @name: the name of the lock
193 * This works like #G_LOCK_DEFINE, but it creates a static object.
198 * @name: the name of the lock
200 * This declares a lock, that is defined with #G_LOCK_DEFINE in another
206 * @name: the name of the lock
208 * Works like g_mutex_lock(), but for a lock defined with
214 * @name: the name of the lock
216 * Works like g_mutex_trylock(), but for a lock defined with
219 * Returns: %TRUE, if the lock could be locked.
224 * @name: the name of the lock
226 * Works like g_mutex_unlock(), but for a lock defined with
230 /* GMutex Documentation {{{1 ------------------------------------------ */
235 * The #GMutex struct is an opaque data structure to represent a mutex
236 * (mutual exclusion). It can be used to protect data against shared
237 * access. Take for example the following function:
240 * <title>A function which will not work in a threaded environment</title>
243 * give_me_next_number (void)
245 * static int current_number = 0;
247 * /<!-- -->* now do a very complicated calculation to calculate the new
248 * * number, this might for example be a random number generator
250 * current_number = calc_next_number (current_number);
252 * return current_number;
257 * It is easy to see that this won't work in a multi-threaded
258 * application. There current_number must be protected against shared
259 * access. A #GMutex can be used as a solution to this problem:
262 * <title>Using GMutex to protected a shared variable</title>
265 * give_me_next_number (void)
267 * static GMutex mutex;
268 * static int current_number = 0;
271 * g_mutex_lock (&mutex);
272 * ret_val = current_number = calc_next_number (current_number);
273 * g_mutex_unlock (&mutex);
280 * Notice that the #GMutex is not initialised to any particular value.
281 * Its placement in static storage ensures that it will be initialised
282 * to all-zeros, which is appropriate.
284 * If a #GMutex is placed in other contexts (eg: embedded in a struct)
285 * then it must be explicitly initialised using g_mutex_init().
287 * A #GMutex should only be accessed via <function>g_mutex_</function>
291 /* GRecMutex Documentation {{{1 -------------------------------------- */
296 * The GRecMutex struct is an opaque data structure to represent a
297 * recursive mutex. It is similar to a #GMutex with the difference
298 * that it is possible to lock a GRecMutex multiple times in the same
299 * thread without deadlock. When doing so, care has to be taken to
300 * unlock the recursive mutex as often as it has been locked.
302 * If a #GRecMutex is allocated in static storage then it can be used
303 * without initialisation. Otherwise, you should call
304 * g_rec_mutex_init() on it and g_rec_mutex_clear() when done.
306 * A GRecMutex should only be accessed with the
307 * <function>g_rec_mutex_</function> functions.
312 /* GRWLock Documentation {{{1 ---------------------------------------- */
317 * The GRWLock struct is an opaque data structure to represent a
318 * reader-writer lock. It is similar to a #GMutex in that it allows
319 * multiple threads to coordinate access to a shared resource.
321 * The difference to a mutex is that a reader-writer lock discriminates
322 * between read-only ('reader') and full ('writer') access. While only
323 * one thread at a time is allowed write access (by holding the 'writer'
324 * lock via g_rw_lock_writer_lock()), multiple threads can gain
325 * simultaneous read-only access (by holding the 'reader' lock via
326 * g_rw_lock_reader_lock()).
329 * <title>An array with access functions</title>
335 * my_array_get (guint index)
337 * gpointer retval = NULL;
342 * g_rw_lock_reader_lock (&lock);
343 * if (index < array->len)
344 * retval = g_ptr_array_index (array, index);
345 * g_rw_lock_reader_unlock (&lock);
351 * my_array_set (guint index, gpointer data)
353 * g_rw_lock_writer_lock (&lock);
356 * array = g_ptr_array_new (<!-- -->);
358 * if (index >= array->len)
359 * g_ptr_array_set_size (array, index+1);
360 * g_ptr_array_index (array, index) = data;
362 * g_rw_lock_writer_unlock (&lock);
366 * This example shows an array which can be accessed by many readers
367 * (the <function>my_array_get()</function> function) simultaneously,
368 * whereas the writers (the <function>my_array_set()</function>
369 * function) will only be allowed once at a time and only if no readers
370 * currently access the array. This is because of the potentially
371 * dangerous resizing of the array. Using these functions is fully
372 * multi-thread safe now.
376 * If a #GRWLock is allocated in static storage then it can be used
377 * without initialisation. Otherwise, you should call
378 * g_rw_lock_init() on it and g_rw_lock_clear() when done.
380 * A GRWLock should only be accessed with the
381 * <function>g_rw_lock_</function> functions.
386 /* GCond Documentation {{{1 ------------------------------------------ */
391 * The #GCond struct is an opaque data structure that represents a
392 * condition. Threads can block on a #GCond if they find a certain
393 * condition to be false. If other threads change the state of this
394 * condition they signal the #GCond, and that causes the waiting
395 * threads to be woken up.
397 * Consider the following example of a shared variable. One or more
398 * threads can wait for data to be published to the variable and when
399 * another thread publishes the data, it can signal one of the waiting
400 * threads to wake up to collect the data.
404 * Using GCond to block a thread until a condition is satisfied
407 * gpointer current_data = NULL;
412 * push_data (gpointer data)
414 * g_mutex_lock (&data_mutex);
415 * current_data = data;
416 * g_cond_signal (&data_cond);
417 * g_mutex_unlock (&data_mutex);
425 * g_mutex_lock (&data_mutex);
426 * while (!current_data)
427 * g_cond_wait (&data_cond, &data_mutex);
428 * data = current_data;
429 * current_data = NULL;
430 * g_mutex_unlock (&data_mutex);
437 * Whenever a thread calls pop_data() now, it will wait until
438 * current_data is non-%NULL, i.e. until some other thread
439 * has called push_data().
441 * The example shows that use of a condition variable must always be
442 * paired with a mutex. Without the use of a mutex, there would be a
443 * race between the check of <varname>current_data</varname> by the
444 * while loop in <function>pop_data</function> and waiting.
445 * Specifically, another thread could set <varname>pop_data</varname>
446 * after the check, and signal the cond (with nobody waiting on it)
447 * before the first thread goes to sleep. #GCond is specifically useful
448 * for its ability to release the mutex and go to sleep atomically.
450 * It is also important to use the g_cond_wait() and g_cond_wait_until()
451 * functions only inside a loop which checks for the condition to be
452 * true. See g_cond_wait() for an explanation of why the condition may
453 * not be true even after it returns.
455 * If a #GCond is allocated in static storage then it can be used
456 * without initialisation. Otherwise, you should call g_cond_init() on
457 * it and g_cond_clear() when done.
459 * A #GCond should only be accessed via the <function>g_cond_</function>
463 /* GThread Documentation {{{1 ---------------------------------------- */
468 * The #GThread struct represents a running thread. This struct
469 * is returned by g_thread_new() or g_thread_try_new(). You can
470 * obtain the #GThread struct representing the current thead by
471 * calling g_thread_self().
473 * GThread is refcounted, see g_thread_ref() and g_thread_unref().
474 * The thread represented by it holds a reference while it is running,
475 * and g_thread_join() consumes the reference that it is given, so
476 * it is normally not necessary to manage GThread references
479 * The structure is opaque -- none of its fields may be directly
485 * @data: data passed to the thread
487 * Specifies the type of the @func functions passed to g_thread_new()
488 * or g_thread_try_new().
490 * Returns: the return value of the thread
494 * g_thread_supported:
496 * This macro returns %TRUE if the thread system is initialized,
497 * and %FALSE if it is not.
499 * For language bindings, g_thread_get_initialized() provides
500 * the same functionality as a function.
502 * Returns: %TRUE, if the thread system is initialized
505 /* GThreadError {{{1 ------------------------------------------------------- */
508 * @G_THREAD_ERROR_AGAIN: a thread couldn't be created due to resource
509 * shortage. Try again later.
511 * Possible errors of thread related functions.
517 * The error domain of the GLib thread subsystem.
519 G_DEFINE_QUARK (g_thread_error, g_thread_error)
521 /* Local Data {{{1 -------------------------------------------------------- */
523 static GMutex g_once_mutex;
524 static GCond g_once_cond;
525 static GSList *g_once_init_list = NULL;
527 static void g_thread_cleanup (gpointer data);
528 static GPrivate g_thread_specific_private = G_PRIVATE_INIT (g_thread_cleanup);
530 G_LOCK_DEFINE_STATIC (g_thread_new);
532 /* GOnce {{{1 ------------------------------------------------------------- */
536 * @status: the status of the #GOnce
537 * @retval: the value returned by the call to the function, if @status
538 * is %G_ONCE_STATUS_READY
540 * A #GOnce struct controls a one-time initialization function. Any
541 * one-time initialization function must have its own unique #GOnce
550 * A #GOnce must be initialized with this macro before it can be used.
553 * GOnce my_once = G_ONCE_INIT;
561 * @G_ONCE_STATUS_NOTCALLED: the function has not been called yet.
562 * @G_ONCE_STATUS_PROGRESS: the function call is currently in progress.
563 * @G_ONCE_STATUS_READY: the function has been called.
565 * The possible statuses of a one-time initialization function
566 * controlled by a #GOnce struct.
573 * @once: a #GOnce structure
574 * @func: the #GThreadFunc function associated to @once. This function
575 * is called only once, regardless of the number of times it and
576 * its associated #GOnce struct are passed to g_once().
577 * @arg: data to be passed to @func
579 * The first call to this routine by a process with a given #GOnce
580 * struct calls @func with the given argument. Thereafter, subsequent
581 * calls to g_once() with the same #GOnce struct do not call @func
582 * again, but return the stored result of the first call. On return
583 * from g_once(), the status of @once will be %G_ONCE_STATUS_READY.
585 * For example, a mutex or a thread-specific data key must be created
586 * exactly once. In a threaded environment, calling g_once() ensures
587 * that the initialization is serialized across multiple threads.
589 * Calling g_once() recursively on the same #GOnce struct in
590 * @func will lead to a deadlock.
594 * get_debug_flags (void)
596 * static GOnce my_once = G_ONCE_INIT;
598 * g_once (&my_once, parse_debug_flags, NULL);
600 * return my_once.retval;
607 g_once_impl (GOnce *once,
611 g_mutex_lock (&g_once_mutex);
613 while (once->status == G_ONCE_STATUS_PROGRESS)
614 g_cond_wait (&g_once_cond, &g_once_mutex);
616 if (once->status != G_ONCE_STATUS_READY)
618 once->status = G_ONCE_STATUS_PROGRESS;
619 g_mutex_unlock (&g_once_mutex);
621 once->retval = func (arg);
623 g_mutex_lock (&g_once_mutex);
624 once->status = G_ONCE_STATUS_READY;
625 g_cond_broadcast (&g_once_cond);
628 g_mutex_unlock (&g_once_mutex);
635 * @location: location of a static initializable variable containing 0
637 * Function to be called when starting a critical initialization
638 * section. The argument @location must point to a static
639 * 0-initialized variable that will be set to a value other than 0 at
640 * the end of the initialization section. In combination with
641 * g_once_init_leave() and the unique address @value_location, it can
642 * be ensured that an initialization section will be executed only once
643 * during a program's life time, and that concurrent threads are
644 * blocked until initialization completed. To be used in constructs
648 * static gsize initialization_value = 0;
650 * if (g_once_init_enter (&initialization_value))
652 * gsize setup_value = 42; /** initialization code here **/
654 * g_once_init_leave (&initialization_value, setup_value);
657 * /** use initialization_value here **/
660 * Returns: %TRUE if the initialization section should be entered,
661 * %FALSE and blocks otherwise
666 (g_once_init_enter) (volatile void *location)
668 volatile gsize *value_location = location;
669 gboolean need_init = FALSE;
670 g_mutex_lock (&g_once_mutex);
671 if (g_atomic_pointer_get (value_location) == NULL)
673 if (!g_slist_find (g_once_init_list, (void*) value_location))
676 g_once_init_list = g_slist_prepend (g_once_init_list, (void*) value_location);
680 g_cond_wait (&g_once_cond, &g_once_mutex);
681 while (g_slist_find (g_once_init_list, (void*) value_location));
683 g_mutex_unlock (&g_once_mutex);
689 * @location: location of a static initializable variable containing 0
690 * @result: new non-0 value for *@value_location
692 * Counterpart to g_once_init_enter(). Expects a location of a static
693 * 0-initialized initialization variable, and an initialization value
694 * other than 0. Sets the variable to the initialization value, and
695 * releases concurrent threads blocking in g_once_init_enter() on this
696 * initialization variable.
701 (g_once_init_leave) (volatile void *location,
704 volatile gsize *value_location = location;
706 g_return_if_fail (g_atomic_pointer_get (value_location) == NULL);
707 g_return_if_fail (result != 0);
708 g_return_if_fail (g_once_init_list != NULL);
710 g_atomic_pointer_set (value_location, result);
711 g_mutex_lock (&g_once_mutex);
712 g_once_init_list = g_slist_remove (g_once_init_list, (void*) value_location);
713 g_cond_broadcast (&g_once_cond);
714 g_mutex_unlock (&g_once_mutex);
717 /* GThread {{{1 -------------------------------------------------------- */
721 * @thread: a #GThread
723 * Increase the reference count on @thread.
725 * Returns: a new reference to @thread
730 g_thread_ref (GThread *thread)
732 GRealThread *real = (GRealThread *) thread;
734 g_atomic_int_inc (&real->ref_count);
741 * @thread: a #GThread
743 * Decrease the reference count on @thread, possibly freeing all
744 * resources associated with it.
746 * Note that each thread holds a reference to its #GThread while
747 * it is running, so it is safe to drop your own reference to it
748 * if you don't need it anymore.
753 g_thread_unref (GThread *thread)
755 GRealThread *real = (GRealThread *) thread;
757 if (g_atomic_int_dec_and_test (&real->ref_count))
760 g_system_thread_free (real);
762 g_slice_free (GRealThread, real);
767 g_thread_cleanup (gpointer data)
769 g_thread_unref (data);
773 g_thread_proxy (gpointer data)
775 GRealThread* thread = data;
779 /* This has to happen before G_LOCK, as that might call g_thread_self */
780 g_private_set (&g_thread_specific_private, data);
782 /* The lock makes sure that g_thread_new_internal() has a chance to
783 * setup 'func' and 'data' before we make the call.
785 G_LOCK (g_thread_new);
786 G_UNLOCK (g_thread_new);
790 g_system_thread_set_name (thread->name);
791 g_free (thread->name);
795 thread->retval = thread->thread.func (thread->thread.data);
802 * @name: (allow-none): an (optional) name for the new thread
803 * @func: a function to execute in the new thread
804 * @data: an argument to supply to the new thread
806 * This function creates a new thread. The new thread starts by invoking
807 * @func with the argument data. The thread will run until @func returns
808 * or until g_thread_exit() is called from the new thread. The return value
809 * of @func becomes the return value of the thread, which can be obtained
810 * with g_thread_join().
812 * The @name can be useful for discriminating threads in a debugger.
813 * It is not used for other purposes and does not have to be unique.
814 * Some systems restrict the length of @name to 16 bytes.
816 * If the thread can not be created the program aborts. See
817 * g_thread_try_new() if you want to attempt to deal with failures.
819 * To free the struct returned by this function, use g_thread_unref().
820 * Note that g_thread_join() implicitly unrefs the #GThread as well.
822 * Returns: the new #GThread
827 g_thread_new (const gchar *name,
831 GError *error = NULL;
834 thread = g_thread_new_internal (name, g_thread_proxy, func, data, 0, &error);
836 if G_UNLIKELY (thread == NULL)
837 g_error ("creating thread '%s': %s", name ? name : "", error->message);
844 * @name: (allow-none): an (optional) name for the new thread
845 * @func: a function to execute in the new thread
846 * @data: an argument to supply to the new thread
847 * @error: return location for error, or %NULL
849 * This function is the same as g_thread_new() except that
850 * it allows for the possibility of failure.
852 * If a thread can not be created (due to resource limits),
853 * @error is set and %NULL is returned.
855 * Returns: the new #GThread, or %NULL if an error occurred
860 g_thread_try_new (const gchar *name,
865 return g_thread_new_internal (name, g_thread_proxy, func, data, 0, error);
869 g_thread_new_internal (const gchar *name,
878 g_return_val_if_fail (func != NULL, NULL);
880 G_LOCK (g_thread_new);
881 thread = g_system_thread_new (proxy, stack_size, error);
884 thread->ref_count = 2;
886 thread->thread.joinable = TRUE;
887 thread->thread.func = func;
888 thread->thread.data = data;
889 thread->name = g_strdup (name);
891 G_UNLOCK (g_thread_new);
893 return (GThread*) thread;
898 * @retval: the return value of this thread
900 * Terminates the current thread.
902 * If another thread is waiting for us using g_thread_join() then the
903 * waiting thread will be woken up and get @retval as the return value
904 * of g_thread_join().
906 * Calling <literal>g_thread_exit (retval)</literal> is equivalent to
907 * returning @retval from the function @func, as given to g_thread_new().
909 * You must only call g_thread_exit() from a thread that you created
910 * yourself with g_thread_new() or related APIs. You must not call
911 * this function from a thread created with another threading library
912 * or or from within a #GThreadPool.
915 g_thread_exit (gpointer retval)
917 GRealThread* real = (GRealThread*) g_thread_self ();
919 if G_UNLIKELY (!real->ours)
920 g_error ("attempt to g_thread_exit() a thread not created by GLib");
922 real->retval = retval;
924 g_system_thread_exit ();
929 * @thread: a #GThread
931 * Waits until @thread finishes, i.e. the function @func, as
932 * given to g_thread_new(), returns or g_thread_exit() is called.
933 * If @thread has already terminated, then g_thread_join()
934 * returns immediately.
936 * Any thread can wait for any other thread by calling g_thread_join(),
937 * not just its 'creator'. Calling g_thread_join() from multiple threads
938 * for the same @thread leads to undefined behaviour.
940 * The value returned by @func or given to g_thread_exit() is
941 * returned by this function.
943 * g_thread_join() consumes the reference to the passed-in @thread.
944 * This will usually cause the #GThread struct and associated resources
945 * to be freed. Use g_thread_ref() to obtain an extra reference if you
946 * want to keep the GThread alive beyond the g_thread_join() call.
948 * Returns: the return value of the thread
951 g_thread_join (GThread *thread)
953 GRealThread *real = (GRealThread*) thread;
956 g_return_val_if_fail (thread, NULL);
957 g_return_val_if_fail (real->ours, NULL);
959 g_system_thread_wait (real);
961 retval = real->retval;
963 /* Just to make sure, this isn't used any more */
964 thread->joinable = 0;
966 g_thread_unref (thread);
974 * This functions returns the #GThread corresponding to the
975 * current thread. Note that this function does not increase
976 * the reference count of the returned struct.
978 * This function will return a #GThread even for threads that
979 * were not created by GLib (i.e. those created by other threading
980 * APIs). This may be useful for thread identification purposes
981 * (i.e. comparisons) but you must not use GLib functions (such
982 * as g_thread_join()) on these threads.
984 * Returns: the #GThread representing the current thread
989 GRealThread* thread = g_private_get (&g_thread_specific_private);
993 /* If no thread data is available, provide and set one.
994 * This can happen for the main thread and for threads
995 * that are not created by GLib.
997 thread = g_slice_new0 (GRealThread);
998 thread->ref_count = 1;
1000 g_private_set (&g_thread_specific_private, thread);
1003 return (GThread*) thread;
1007 * g_get_num_processors:
1009 * Determine the approximate number of threads that the system will
1010 * schedule simultaneously for this process. This is intended to be
1011 * used as a parameter to g_thread_pool_new() for CPU bound tasks and
1014 * Returns: Number of schedulable threads, always greater than 0
1019 g_get_num_processors (void)
1022 DWORD_PTR process_cpus;
1023 DWORD_PTR system_cpus;
1025 if (GetProcessAffinityMask (GetCurrentProcess (),
1026 &process_cpus, &system_cpus))
1030 for (count = 0; process_cpus != 0; process_cpus >>= 1)
1031 if (process_cpus & 1)
1037 #elif defined(_SC_NPROCESSORS_ONLN)
1041 count = sysconf (_SC_NPROCESSORS_ONLN);
1045 #elif defined HW_NCPU
1047 int mib[2], count = 0;
1052 len = sizeof(count);
1054 if (sysctl (mib, 2, &count, &len, NULL, 0) == 0 && count > 0)
1059 return 1; /* Fallback */
1063 /* vim: set foldmethod=marker: */