glib/gthread.c

   1 /* GLIB - Library of useful routines for C programming
   2  * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
   3  *
   4  * gthread.c: MT safety related functions
   5  * Copyright 1998 Sebastian Wilhelmi; University of Karlsruhe
   6  *                Owen Taylor
   7  *
   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.
  12  *
  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.
  17  *
  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.
  22  */
  23
  24 /*
  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/.
  29  */
  30
  31 /*
  32  * MT safe
  33  */
  34
  35 #include "config.h"
  36
  37 #ifdef HAVE_UNISTD_H
  38 #include <unistd.h>
  39 #endif
  40
  41 #include <string.h>
  42
  43 #include "galias.h"
  44 #include "glib.h"
  45 #include "gthreadinit.h"
  46
  47 #if GLIB_SIZEOF_SYSTEM_THREAD == SIZEOF_VOID_P
  48 # define g_system_thread_equal_simple(thread1, thread2)                 \
  49    ((thread1).dummy_pointer == (thread2).dummy_pointer)
  50 # define g_system_thread_assign(dest, src)                              \
  51    ((dest).dummy_pointer = (src).dummy_pointer)
  52 #else /* GLIB_SIZEOF_SYSTEM_THREAD != SIZEOF_VOID_P */
  53 # define g_system_thread_equal_simple(thread1, thread2)                 \
  54    (memcmp (&(thread1), &(thread2), GLIB_SIZEOF_SYSTEM_THREAD) == 0)
  55 # define g_system_thread_assign(dest, src)                              \
  56    (memcpy (&(dest), &(src), GLIB_SIZEOF_SYSTEM_THREAD))
  57 #endif /* GLIB_SIZEOF_SYSTEM_THREAD == SIZEOF_VOID_P */
  58
  59 #define g_system_thread_equal(thread1, thread2)                         \
  60   (g_thread_functions_for_glib_use.thread_equal ?                       \
  61    g_thread_functions_for_glib_use.thread_equal (&(thread1), &(thread2)) :\
  62    g_system_thread_equal_simple((thread1), (thread2)))
  63
  64 GQuark
  65 g_thread_error_quark (void)
  66 {
  67   static GQuark quark;
  68   if (!quark)
  69     quark = g_quark_from_static_string ("g_thread_error");
  70   return quark;
  71 }
  72
  73 /* Keep this in sync with GRealThread in gmain.c! */
  74 typedef struct _GRealThread GRealThread;
  75 struct  _GRealThread
  76 {
  77   GThread thread;
  78   gpointer private_data;
  79   gpointer retval;
  80   GSystemThread system_thread;
  81 };
  82
  83 typedef struct _GStaticPrivateNode GStaticPrivateNode;
  84 struct _GStaticPrivateNode
  85 {
  86   gpointer       data;
  87   GDestroyNotify destroy;
  88 };
  89
  90 static void g_thread_cleanup (gpointer data);
  91 static void g_thread_fail (void);
  92
  93 /* Global variables */
  94
  95 static GSystemThread zero_thread; /* This is initialized to all zero */
  96 gboolean g_thread_use_default_impl = TRUE;
  97 gboolean g_threads_got_initialized = FALSE;
  98
  99 GThreadFunctions g_thread_functions_for_glib_use = {
 100   (GMutex*(*)())g_thread_fail,                 /* mutex_new */
 101   NULL,                                        /* mutex_lock */
 102   NULL,                                        /* mutex_trylock */
 103   NULL,                                        /* mutex_unlock */
 104   NULL,                                        /* mutex_free */
 105   (GCond*(*)())g_thread_fail,                  /* cond_new */
 106   NULL,                                        /* cond_signal */
 107   NULL,                                        /* cond_broadcast */
 108   NULL,                                        /* cond_wait */
 109   NULL,                                        /* cond_timed_wait  */
 110   NULL,                                        /* cond_free */
 111   (GPrivate*(*)(GDestroyNotify))g_thread_fail, /* private_new */
 112   NULL,                                        /* private_get */
 113   NULL,                                        /* private_set */
 114   (void(*)(GThreadFunc, gpointer, gulong,
 115            gboolean, gboolean, GThreadPriority,
 116            gpointer, GError**))g_thread_fail,  /* thread_create */
 117   NULL,                                        /* thread_yield */
 118   NULL,                                        /* thread_join */
 119   NULL,                                        /* thread_exit */
 120   NULL,                                        /* thread_set_priority */
 121   NULL                                         /* thread_self */
 122 };
 123
 124 /* Local data */
 125
 126 static GMutex   *g_once_mutex = NULL;
 127 static GCond    *g_once_cond = NULL;
 128 static GPrivate *g_thread_specific_private = NULL;
 129 static GSList   *g_thread_all_threads = NULL;
 130 static GSList   *g_thread_free_indeces = NULL;
 131
 132 G_LOCK_DEFINE_STATIC (g_thread);
 133
 134 #ifdef G_THREADS_ENABLED
 135 /* This must be called only once, before any threads are created.
 136  * It will only be called from g_thread_init() in -lgthread.
 137  */
 138 void
 139 g_thread_init_glib (void)
 140 {
 141   /* We let the main thread (the one that calls g_thread_init) inherit
 142    * the static_private data set before calling g_thread_init
 143    */
 144   GRealThread* main_thread = (GRealThread*) g_thread_self ();
 145
 146   g_once_mutex = g_mutex_new ();
 147   g_once_cond = g_cond_new ();
 148
 149   _g_convert_thread_init ();
 150   _g_rand_thread_init ();
 151   _g_main_thread_init ();
 152   _g_mem_thread_init ();
 153   _g_messages_thread_init ();
 154   _g_atomic_thread_init ();
 155   _g_win32_thread_init ();
 156
 157   g_threads_got_initialized = TRUE;
 158
 159   g_thread_specific_private = g_private_new (g_thread_cleanup);
 160   g_private_set (g_thread_specific_private, main_thread);
 161   G_THREAD_UF (thread_self, (&main_thread->system_thread));
 162
 163   _g_mem_thread_private_init ();
 164   _g_messages_thread_private_init ();
 165
 166 }
 167 #endif /* G_THREADS_ENABLED */
 168
 169 gpointer
 170 g_once_impl (GOnce       *once,
 171              GThreadFunc  func,
 172              gpointer     arg)
 173 {
 174   g_mutex_lock (g_once_mutex);
 175
 176   while (once->status == G_ONCE_STATUS_PROGRESS)
 177     g_cond_wait (g_once_cond, g_once_mutex);
 178
 179   if (once->status != G_ONCE_STATUS_READY)
 180     {
 181       once->status = G_ONCE_STATUS_PROGRESS;
 182       g_mutex_unlock (g_once_mutex);
 183
 184       once->retval = func (arg);
 185
 186       g_mutex_lock (g_once_mutex);
 187       once->status = G_ONCE_STATUS_READY;
 188       g_cond_broadcast (g_once_cond);
 189     }
 190
 191   g_mutex_unlock (g_once_mutex);
 192
 193   return once->retval;
 194 }
 195
 196 void
 197 g_static_mutex_init (GStaticMutex *mutex)
 198 {
 199   static GStaticMutex init_mutex = G_STATIC_MUTEX_INIT;
 200
 201   g_return_if_fail (mutex);
 202
 203   *mutex = init_mutex;
 204 }
 205
 206 GMutex *
 207 g_static_mutex_get_mutex_impl (GMutex** mutex)
 208 {
 209   if (!g_thread_supported ())
 210     return NULL;
 211
 212   g_assert (g_once_mutex);
 213
 214   g_mutex_lock (g_once_mutex);
 215
 216   if (!(*mutex))
 217     {
 218       GMutex *new_mutex = g_mutex_new ();
 219
 220       /* The following is a memory barrier to avoid the write
 221        * to *new_mutex being reordered to after writing *mutex */
 222       g_mutex_lock (new_mutex);
 223       g_mutex_unlock (new_mutex);
 224
 225       *mutex = new_mutex;
 226     }
 227
 228   g_mutex_unlock (g_once_mutex);
 229
 230   return *mutex;
 231 }
 232
 233 void
 234 g_static_mutex_free (GStaticMutex* mutex)
 235 {
 236   GMutex **runtime_mutex;
 237
 238   g_return_if_fail (mutex);
 239
 240   /* The runtime_mutex is the first (or only) member of GStaticMutex,
 241    * see both versions (of glibconfig.h) in configure.in */
 242   runtime_mutex = ((GMutex**)mutex);
 243
 244   if (*runtime_mutex)
 245     g_mutex_free (*runtime_mutex);
 246
 247   *runtime_mutex = NULL;
 248 }
 249
 250 void
 251 g_static_rec_mutex_init (GStaticRecMutex *mutex)
 252 {
 253   static GStaticRecMutex init_mutex = G_STATIC_REC_MUTEX_INIT;
 254
 255   g_return_if_fail (mutex);
 256
 257   *mutex = init_mutex;
 258 }
 259
 260 void
 261 g_static_rec_mutex_lock (GStaticRecMutex* mutex)
 262 {
 263   GSystemThread self;
 264
 265   g_return_if_fail (mutex);
 266
 267   if (!g_thread_supported ())
 268     return;
 269
 270   G_THREAD_UF (thread_self, (&self));
 271
 272   if (g_system_thread_equal (self, mutex->owner))
 273     {
 274       mutex->depth++;
 275       return;
 276     }
 277   g_static_mutex_lock (&mutex->mutex);
 278   g_system_thread_assign (mutex->owner, self);
 279   mutex->depth = 1;
 280 }
 281
 282 gboolean
 283 g_static_rec_mutex_trylock (GStaticRecMutex* mutex)
 284 {
 285   GSystemThread self;
 286
 287   g_return_val_if_fail (mutex, FALSE);
 288
 289   if (!g_thread_supported ())
 290     return TRUE;
 291
 292   G_THREAD_UF (thread_self, (&self));
 293
 294   if (g_system_thread_equal (self, mutex->owner))
 295     {
 296       mutex->depth++;
 297       return TRUE;
 298     }
 299
 300   if (!g_static_mutex_trylock (&mutex->mutex))
 301     return FALSE;
 302
 303   g_system_thread_assign (mutex->owner, self);
 304   mutex->depth = 1;
 305   return TRUE;
 306 }
 307
 308 void
 309 g_static_rec_mutex_unlock (GStaticRecMutex* mutex)
 310 {
 311   g_return_if_fail (mutex);
 312
 313   if (!g_thread_supported ())
 314     return;
 315
 316   if (mutex->depth > 1)
 317     {
 318       mutex->depth--;
 319       return;
 320     }
 321   g_system_thread_assign (mutex->owner, zero_thread);
 322   g_static_mutex_unlock (&mutex->mutex);
 323 }
 324
 325 void
 326 g_static_rec_mutex_lock_full   (GStaticRecMutex *mutex,
 327                                 guint            depth)
 328 {
 329   GSystemThread self;
 330   g_return_if_fail (mutex);
 331
 332   if (!g_thread_supported ())
 333     return;
 334
 335   G_THREAD_UF (thread_self, (&self));
 336
 337   if (g_system_thread_equal (self, mutex->owner))
 338     {
 339       mutex->depth += depth;
 340       return;
 341     }
 342   g_static_mutex_lock (&mutex->mutex);
 343   g_system_thread_assign (mutex->owner, self);
 344   mutex->depth = depth;
 345 }
 346
 347 guint
 348 g_static_rec_mutex_unlock_full (GStaticRecMutex *mutex)
 349 {
 350   guint depth;
 351
 352   g_return_val_if_fail (mutex, 0);
 353
 354   if (!g_thread_supported ())
 355     return 1;
 356
 357   depth = mutex->depth;
 358
 359   g_system_thread_assign (mutex->owner, zero_thread);
 360   mutex->depth = 0;
 361   g_static_mutex_unlock (&mutex->mutex);
 362
 363   return depth;
 364 }
 365
 366 void
 367 g_static_rec_mutex_free (GStaticRecMutex *mutex)
 368 {
 369   g_return_if_fail (mutex);
 370
 371   g_static_mutex_free (&mutex->mutex);
 372 }
 373
 374 void
 375 g_static_private_init (GStaticPrivate *private_key)
 376 {
 377   private_key->index = 0;
 378 }
 379
 380 gpointer
 381 g_static_private_get (GStaticPrivate *private_key)
 382 {
 383   GRealThread *self = (GRealThread*) g_thread_self ();
 384   GArray *array;
 385
 386   array = self->private_data;
 387   if (!array)
 388     return NULL;
 389
 390   if (!private_key->index)
 391     return NULL;
 392   else if (private_key->index <= array->len)
 393     return g_array_index (array, GStaticPrivateNode,
 394                           private_key->index - 1).data;
 395   else
 396     return NULL;
 397 }
 398
 399 void
 400 g_static_private_set (GStaticPrivate *private_key,
 401                       gpointer        data,
 402                       GDestroyNotify  notify)
 403 {
 404   GRealThread *self = (GRealThread*) g_thread_self ();
 405   GArray *array;
 406   static guint next_index = 0;
 407   GStaticPrivateNode *node;
 408
 409   array = self->private_data;
 410   if (!array)
 411     {
 412       array = g_array_new (FALSE, TRUE, sizeof (GStaticPrivateNode));
 413       self->private_data = array;
 414     }
 415
 416   if (!private_key->index)
 417     {
 418       G_LOCK (g_thread);
 419
 420       if (!private_key->index)
 421         {
 422           if (g_thread_free_indeces)
 423             {
 424               private_key->index =
 425                 GPOINTER_TO_UINT (g_thread_free_indeces->data);
 426               g_thread_free_indeces =
 427                 g_slist_delete_link (g_thread_free_indeces,
 428                                      g_thread_free_indeces);
 429             }
 430           else
 431             private_key->index = ++next_index;
 432         }
 433
 434       G_UNLOCK (g_thread);
 435     }
 436
 437   if (private_key->index > array->len)
 438     g_array_set_size (array, private_key->index);
 439
 440   node = &g_array_index (array, GStaticPrivateNode, private_key->index - 1);
 441   if (node->destroy)
 442     {
 443       gpointer ddata = node->data;
 444       GDestroyNotify ddestroy = node->destroy;
 445
 446       node->data = data;
 447       node->destroy = notify;
 448
 449       ddestroy (ddata);
 450     }
 451   else
 452     {
 453       node->data = data;
 454       node->destroy = notify;
 455     }
 456 }
 457
 458 void
 459 g_static_private_free (GStaticPrivate *private_key)
 460 {
 461   guint index = private_key->index;
 462   GSList *list;
 463
 464   if (!index)
 465     return;
 466
 467   private_key->index = 0;
 468
 469   G_LOCK (g_thread);
 470   list =  g_thread_all_threads;
 471   while (list)
 472     {
 473       GRealThread *thread = list->data;
 474       GArray *array = thread->private_data;
 475       list = list->next;
 476
 477       if (array && index <= array->len)
 478         {
 479           GStaticPrivateNode *node = &g_array_index (array,
 480                                                      GStaticPrivateNode,
 481                                                      index - 1);
 482           gpointer ddata = node->data;
 483           GDestroyNotify ddestroy = node->destroy;
 484
 485           node->data = NULL;
 486           node->destroy = NULL;
 487
 488           if (ddestroy)
 489             {
 490               G_UNLOCK (g_thread);
 491               ddestroy (ddata);
 492               G_LOCK (g_thread);
 493               }
 494         }
 495     }
 496   g_thread_free_indeces = g_slist_prepend (g_thread_free_indeces,
 497                                            GUINT_TO_POINTER (index));
 498   G_UNLOCK (g_thread);
 499 }
 500
 501 static void
 502 g_thread_cleanup (gpointer data)
 503 {
 504   if (data)
 505     {
 506       GRealThread* thread = data;
 507       if (thread->private_data)
 508         {
 509           GArray* array = thread->private_data;
 510           guint i;
 511
 512           for (i = 0; i < array->len; i++ )
 513             {
 514               GStaticPrivateNode *node =
 515                 &g_array_index (array, GStaticPrivateNode, i);
 516               if (node->destroy)
 517                 node->destroy (node->data);
 518             }
 519           g_array_free (array, TRUE);
 520         }
 521
 522       /* We only free the thread structure, if it isn't joinable. If
 523          it is, the structure is freed in g_thread_join */
 524       if (!thread->thread.joinable)
 525         {
 526           G_LOCK (g_thread);
 527           g_thread_all_threads = g_slist_remove (g_thread_all_threads, data);
 528           G_UNLOCK (g_thread);
 529
 530           /* Just to make sure, this isn't used any more */
 531           g_system_thread_assign (thread->system_thread, zero_thread);
 532           g_free (thread);
 533         }
 534     }
 535 }
 536
 537 static void
 538 g_thread_fail (void)
 539 {
 540   g_error ("The thread system is not yet initialized.");
 541 }
 542
 543 static gpointer
 544 g_thread_create_proxy (gpointer data)
 545 {
 546   GRealThread* thread = data;
 547
 548   g_assert (data);
 549
 550   /* This has to happen before G_LOCK, as that might call g_thread_self */
 551   g_private_set (g_thread_specific_private, data);
 552
 553   /* the lock makes sure, that thread->system_thread is written,
 554      before thread->thread.func is called. See g_thread_create. */
 555   G_LOCK (g_thread);
 556   G_UNLOCK (g_thread);
 557
 558   thread->retval = thread->thread.func (thread->thread.data);
 559
 560   return NULL;
 561 }
 562
 563 GThread*
 564 g_thread_create_full (GThreadFunc                func,
 565                       gpointer           data,
 566                       gulong             stack_size,
 567                       gboolean           joinable,
 568                       gboolean           bound,
 569                       GThreadPriority    priority,
 570                       GError                **error)
 571 {
 572   GRealThread* result;
 573   GError *local_error = NULL;
 574   g_return_val_if_fail (func, NULL);
 575   g_return_val_if_fail (priority >= G_THREAD_PRIORITY_LOW, NULL);
 576   g_return_val_if_fail (priority <= G_THREAD_PRIORITY_URGENT, NULL);
 577
 578   result = g_new (GRealThread, 1);
 579
 580   result->thread.joinable = joinable;
 581   result->thread.priority = priority;
 582   result->thread.func = func;
 583   result->thread.data = data;
 584   result->private_data = NULL;
 585   G_LOCK (g_thread);
 586   G_THREAD_UF (thread_create, (g_thread_create_proxy, result,
 587                                stack_size, joinable, bound, priority,
 588                                &result->system_thread, &local_error));
 589   g_thread_all_threads = g_slist_prepend (g_thread_all_threads, result);
 590   G_UNLOCK (g_thread);
 591
 592   if (local_error)
 593     {
 594       g_propagate_error (error, local_error);
 595       g_free (result);
 596       return NULL;
 597     }
 598
 599   return (GThread*) result;
 600 }
 601
 602 void
 603 g_thread_exit (gpointer retval)
 604 {
 605   GRealThread* real = (GRealThread*) g_thread_self ();
 606   real->retval = retval;
 607   G_THREAD_CF (thread_exit, (void)0, ());
 608 }
 609
 610 gpointer
 611 g_thread_join (GThread* thread)
 612 {
 613   GRealThread* real = (GRealThread*) thread;
 614   gpointer retval;
 615
 616   g_return_val_if_fail (thread, NULL);
 617   g_return_val_if_fail (thread->joinable, NULL);
 618   g_return_val_if_fail (!g_system_thread_equal (real->system_thread,
 619                                                 zero_thread), NULL);
 620
 621   G_THREAD_UF (thread_join, (&real->system_thread));
 622
 623   retval = real->retval;
 624
 625   G_LOCK (g_thread);
 626   g_thread_all_threads = g_slist_remove (g_thread_all_threads, thread);
 627   G_UNLOCK (g_thread);
 628
 629   /* Just to make sure, this isn't used any more */
 630   thread->joinable = 0;
 631   g_system_thread_assign (real->system_thread, zero_thread);
 632
 633   /* the thread structure for non-joinable threads is freed upon
 634      thread end. We free the memory here. This will leave a loose end,
 635      if a joinable thread is not joined. */
 636
 637   g_free (thread);
 638
 639   return retval;
 640 }
 641
 642 void
 643 g_thread_set_priority (GThread* thread,
 644                        GThreadPriority priority)
 645 {
 646   GRealThread* real = (GRealThread*) thread;
 647
 648   g_return_if_fail (thread);
 649   g_return_if_fail (!g_system_thread_equal (real->system_thread, zero_thread));
 650   g_return_if_fail (priority >= G_THREAD_PRIORITY_LOW);
 651   g_return_if_fail (priority <= G_THREAD_PRIORITY_URGENT);
 652
 653   thread->priority = priority;
 654
 655   G_THREAD_CF (thread_set_priority, (void)0,
 656                (&real->system_thread, priority));
 657 }
 658
 659 GThread*
 660 g_thread_self (void)
 661 {
 662   GRealThread* thread = g_private_get (g_thread_specific_private);
 663
 664   if (!thread)
 665     {
 666       /* If no thread data is available, provide and set one.  This
 667          can happen for the main thread and for threads, that are not
 668          created by GLib. */
 669       thread = g_new (GRealThread, 1);
 670       thread->thread.joinable = FALSE; /* This is a save guess */
 671       thread->thread.priority = G_THREAD_PRIORITY_NORMAL; /* This is
 672                                                              just a guess */
 673       thread->thread.func = NULL;
 674       thread->thread.data = NULL;
 675       thread->private_data = NULL;
 676
 677       if (g_thread_supported ())
 678         G_THREAD_UF (thread_self, (&thread->system_thread));
 679
 680       g_private_set (g_thread_specific_private, thread);
 681
 682       G_LOCK (g_thread);
 683       g_thread_all_threads = g_slist_prepend (g_thread_all_threads, thread);
 684       G_UNLOCK (g_thread);
 685     }
 686
 687   return (GThread*)thread;
 688 }
 689
 690 void
 691 g_static_rw_lock_init (GStaticRWLock* lock)
 692 {
 693   static GStaticRWLock init_lock = G_STATIC_RW_LOCK_INIT;
 694
 695   g_return_if_fail (lock);
 696
 697   *lock = init_lock;
 698 }
 699
 700 static void inline
 701 g_static_rw_lock_wait (GCond** cond, GStaticMutex* mutex)
 702 {
 703   if (!*cond)
 704       *cond = g_cond_new ();
 705   g_cond_wait (*cond, g_static_mutex_get_mutex (mutex));
 706 }
 707
 708 static void inline
 709 g_static_rw_lock_signal (GStaticRWLock* lock)
 710 {
 711   if (lock->want_to_write && lock->write_cond)
 712     g_cond_signal (lock->write_cond);
 713   else if (lock->want_to_read && lock->read_cond)
 714     g_cond_broadcast (lock->read_cond);
 715 }
 716
 717 void
 718 g_static_rw_lock_reader_lock (GStaticRWLock* lock)
 719 {
 720   g_return_if_fail (lock);
 721
 722   if (!g_threads_got_initialized)
 723     return;
 724
 725   g_static_mutex_lock (&lock->mutex);
 726   lock->want_to_read++;
 727   while (lock->have_writer || lock->want_to_write)
 728     g_static_rw_lock_wait (&lock->read_cond, &lock->mutex);
 729   lock->want_to_read--;
 730   lock->read_counter++;
 731   g_static_mutex_unlock (&lock->mutex);
 732 }
 733
 734 gboolean
 735 g_static_rw_lock_reader_trylock (GStaticRWLock* lock)
 736 {
 737   gboolean ret_val = FALSE;
 738
 739   g_return_val_if_fail (lock, FALSE);
 740
 741   if (!g_threads_got_initialized)
 742     return TRUE;
 743
 744   g_static_mutex_lock (&lock->mutex);
 745   if (!lock->have_writer && !lock->want_to_write)
 746     {
 747       lock->read_counter++;
 748       ret_val = TRUE;
 749     }
 750   g_static_mutex_unlock (&lock->mutex);
 751   return ret_val;
 752 }
 753
 754 void
 755 g_static_rw_lock_reader_unlock  (GStaticRWLock* lock)
 756 {
 757   g_return_if_fail (lock);
 758
 759   if (!g_threads_got_initialized)
 760     return;
 761
 762   g_static_mutex_lock (&lock->mutex);
 763   lock->read_counter--;
 764   if (lock->read_counter == 0)
 765     g_static_rw_lock_signal (lock);
 766   g_static_mutex_unlock (&lock->mutex);
 767 }
 768
 769 void
 770 g_static_rw_lock_writer_lock (GStaticRWLock* lock)
 771 {
 772   g_return_if_fail (lock);
 773
 774   if (!g_threads_got_initialized)
 775     return;
 776
 777   g_static_mutex_lock (&lock->mutex);
 778   lock->want_to_write++;
 779   while (lock->have_writer || lock->read_counter)
 780     g_static_rw_lock_wait (&lock->write_cond, &lock->mutex);
 781   lock->want_to_write--;
 782   lock->have_writer = TRUE;
 783   g_static_mutex_unlock (&lock->mutex);
 784 }
 785
 786 gboolean
 787 g_static_rw_lock_writer_trylock (GStaticRWLock* lock)
 788 {
 789   gboolean ret_val = FALSE;
 790
 791   g_return_val_if_fail (lock, FALSE);
 792
 793   if (!g_threads_got_initialized)
 794     return TRUE;
 795
 796   g_static_mutex_lock (&lock->mutex);
 797   if (!lock->have_writer && !lock->read_counter)
 798     {
 799       lock->have_writer = TRUE;
 800       ret_val = TRUE;
 801     }
 802   g_static_mutex_unlock (&lock->mutex);
 803   return ret_val;
 804 }
 805
 806 void
 807 g_static_rw_lock_writer_unlock (GStaticRWLock* lock)
 808 {
 809   g_return_if_fail (lock);
 810
 811   if (!g_threads_got_initialized)
 812     return;
 813
 814   g_static_mutex_lock (&lock->mutex);
 815   lock->have_writer = FALSE;
 816   g_static_rw_lock_signal (lock);
 817   g_static_mutex_unlock (&lock->mutex);
 818 }
 819
 820 void
 821 g_static_rw_lock_free (GStaticRWLock* lock)
 822 {
 823   g_return_if_fail (lock);
 824
 825   if (lock->read_cond)
 826     {
 827       g_cond_free (lock->read_cond);
 828       lock->read_cond = NULL;
 829     }
 830   if (lock->write_cond)
 831     {
 832       g_cond_free (lock->write_cond);
 833       lock->write_cond = NULL;
 834     }
 835   g_static_mutex_free (&lock->mutex);
 836 }