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  * gmutex.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 #include "glib.h"
  37
  38 #ifdef G_THREAD_USE_PID_SURROGATE
  39 #include <sys/types.h>
  40 #include <sys/time.h>
  41 #include <sys/resource.h>
  42 #include <errno.h>
  43 #endif /* G_THREAD_USE_PID_SURROGATE */
  44
  45 #ifdef HAVE_UNISTD_H
  46 #include <unistd.h>
  47 #endif
  48
  49 #include <string.h>
  50
  51 #if GLIB_SIZEOF_SYSTEM_THREAD == SIZEOF_VOID_P
  52 # define g_system_thread_equal(thread1, thread2)                        \
  53    (thread1.dummy_pointer == thread2.dummy_pointer)
  54 # define g_system_thread_assign(dest, src)                              \
  55    (dest.dummy_pointer = src.dummy_pointer)
  56 #else /* GLIB_SIZEOF_SYSTEM_THREAD != SIZEOF_VOID_P */
  57 # define g_system_thread_equal(thread1, thread2)                        \
  58    (memcmp (&thread1, &thread2, GLIB_SIZEOF_SYSTEM_THREAD) == 0)
  59 # define g_system_thread_assign(dest, src)                              \
  60    (memcpy (&dest, &src, GLIB_SIZEOF_SYSTEM_THREAD))
  61 #endif /* GLIB_SIZEOF_SYSTEM_THREAD == SIZEOF_VOID_P */
  62
  63 GQuark
  64 g_thread_error_quark (void)
  65 {
  66   static GQuark quark;
  67   if (!quark)
  68     quark = g_quark_from_static_string ("g_thread_error");
  69   return quark;
  70 }
  71
  72 /* Keep this in sync with GRealThread in gmain.c! */
  73 typedef struct _GRealThread GRealThread;
  74 struct  _GRealThread
  75 {
  76   GThread thread;
  77   GMainContext *context;
  78   gpointer private_data;
  79   gpointer retval;
  80   GSystemThread system_thread;
  81 #ifdef G_THREAD_USE_PID_SURROGATE
  82   pid_t pid;
  83 #endif /* G_THREAD_USE_PID_SURROGATE */
  84 };
  85
  86 #ifdef G_THREAD_USE_PID_SURROGATE
  87 static gint priority_map[] = { 15, 0, -15, -20 };
  88 static gboolean prio_warned = FALSE;
  89 # define SET_PRIO(pid, prio) G_STMT_START{                              \
  90   gint error = setpriority (PRIO_PROCESS, (pid), priority_map[prio]);   \
  91   if (error == -1 && errno == EACCES && !prio_warned)                   \
  92     {                                                                   \
  93       prio_warned = TRUE;                                               \
  94       g_warning ("Priorities can only be increased by root.");          \
  95     }                                                                   \
  96   }G_STMT_END
  97 #endif /* G_THREAD_USE_PID_SURROGATE */
  98
  99 typedef struct _GStaticPrivateNode GStaticPrivateNode;
 100 struct _GStaticPrivateNode
 101 {
 102   gpointer       data;
 103   GDestroyNotify destroy;
 104 };
 105
 106 static void g_thread_cleanup (gpointer data);
 107 static void g_thread_fail (void);
 108
 109 /* Global variables */
 110
 111 static GSystemThread zero_thread; /* This is initialized to all zero */
 112 gboolean g_thread_use_default_impl = TRUE;
 113 gboolean g_threads_got_initialized = FALSE;
 114
 115 #if defined(G_PLATFORM_WIN32) && defined(__GNUC__)
 116 __declspec(dllexport)
 117 #endif
 118 GThreadFunctions g_thread_functions_for_glib_use = {
 119   (GMutex*(*)())g_thread_fail,                 /* mutex_new */
 120   NULL,                                        /* mutex_lock */
 121   NULL,                                        /* mutex_trylock */
 122   NULL,                                        /* mutex_unlock */
 123   NULL,                                        /* mutex_free */
 124   (GCond*(*)())g_thread_fail,                  /* cond_new */
 125   NULL,                                        /* cond_signal */
 126   NULL,                                        /* cond_broadcast */
 127   NULL,                                        /* cond_wait */
 128   NULL,                                        /* cond_timed_wait  */
 129   NULL,                                        /* cond_free */
 130   (GPrivate*(*)(GDestroyNotify))g_thread_fail, /* private_new */
 131   NULL,                                        /* private_get */
 132   NULL,                                        /* private_set */
 133   (void(*)(GThreadFunc, gpointer, gulong,
 134            gboolean, gboolean, GThreadPriority,
 135            gpointer, GError**))g_thread_fail,  /* thread_create */
 136   NULL,                                        /* thread_yield */
 137   NULL,                                        /* thread_join */
 138   NULL,                                        /* thread_exit */
 139   NULL,                                        /* thread_set_priority */
 140   NULL                                         /* thread_self */
 141 };
 142
 143 /* Local data */
 144
 145 static GMutex   *g_mutex_protect_static_mutex_allocation = NULL;
 146 static GPrivate *g_thread_specific_private = NULL;
 147 static GSList   *g_thread_all_threads = NULL;
 148 static GSList   *g_thread_free_indeces = NULL;
 149
 150 G_LOCK_DEFINE_STATIC (g_thread);
 151
 152 /* This must be called only once, before any threads are created.
 153  * It will only be called from g_thread_init() in -lgthread.
 154  */
 155 void
 156 g_mutex_init (void)
 157 {
 158   GRealThread* main_thread;
 159
 160   /* We let the main thread (the one that calls g_thread_init) inherit
 161    * the data, that it set before calling g_thread_init
 162    */
 163   main_thread = (GRealThread*) g_thread_self ();
 164
 165   g_thread_specific_private = g_private_new (g_thread_cleanup);
 166   G_THREAD_UF (private_set, (g_thread_specific_private, main_thread));
 167   G_THREAD_UF (thread_self, (&main_thread->system_thread));
 168
 169   g_mutex_protect_static_mutex_allocation = g_mutex_new ();
 170 }
 171
 172 void
 173 g_static_mutex_init (GStaticMutex *mutex)
 174 {
 175   static GStaticMutex init_mutex = G_STATIC_MUTEX_INIT;
 176
 177   g_return_if_fail (mutex);
 178
 179   *mutex = init_mutex;
 180 }
 181
 182 GMutex *
 183 g_static_mutex_get_mutex_impl (GMutex** mutex)
 184 {
 185   if (!g_thread_supported ())
 186     return NULL;
 187
 188   g_assert (g_mutex_protect_static_mutex_allocation);
 189
 190   g_mutex_lock (g_mutex_protect_static_mutex_allocation);
 191
 192   if (!(*mutex))
 193     *mutex = g_mutex_new ();
 194
 195   g_mutex_unlock (g_mutex_protect_static_mutex_allocation);
 196
 197   return *mutex;
 198 }
 199
 200 void
 201 g_static_mutex_free (GStaticMutex* mutex)
 202 {
 203   GMutex **runtime_mutex;
 204
 205   g_return_if_fail (mutex);
 206
 207   /* The runtime_mutex is the first (or only) member of GStaticMutex,
 208    * see both versions (of glibconfig.h) in configure.in */
 209   runtime_mutex = ((GMutex**)mutex);
 210
 211   if (*runtime_mutex)
 212     g_mutex_free (*runtime_mutex);
 213
 214   *runtime_mutex = NULL;
 215 }
 216
 217 void
 218 g_static_rec_mutex_init (GStaticRecMutex *mutex)
 219 {
 220   static GStaticRecMutex init_mutex = G_STATIC_REC_MUTEX_INIT;
 221
 222   g_return_if_fail (mutex);
 223
 224   *mutex = init_mutex;
 225 }
 226
 227 void
 228 g_static_rec_mutex_lock (GStaticRecMutex* mutex)
 229 {
 230   GSystemThread self;
 231
 232   g_return_if_fail (mutex);
 233
 234   if (!g_thread_supported ())
 235     return;
 236
 237   G_THREAD_UF (thread_self, (&self));
 238
 239   if (g_system_thread_equal (self, mutex->owner))
 240     {
 241       mutex->depth++;
 242       return;
 243     }
 244   g_static_mutex_lock (&mutex->mutex);
 245   g_system_thread_assign (mutex->owner, self);
 246   mutex->depth = 1;
 247 }
 248
 249 gboolean
 250 g_static_rec_mutex_trylock (GStaticRecMutex* mutex)
 251 {
 252   GSystemThread self;
 253
 254   g_return_val_if_fail (mutex, FALSE);
 255
 256   if (!g_thread_supported ())
 257     return TRUE;
 258
 259   G_THREAD_UF (thread_self, (&self));
 260
 261   if (g_system_thread_equal (self, mutex->owner))
 262     {
 263       mutex->depth++;
 264       return TRUE;
 265     }
 266
 267   if (!g_static_mutex_trylock (&mutex->mutex))
 268     return FALSE;
 269
 270   g_system_thread_assign (mutex->owner, self);
 271   mutex->depth = 1;
 272   return TRUE;
 273 }
 274
 275 void
 276 g_static_rec_mutex_unlock (GStaticRecMutex* mutex)
 277 {
 278   g_return_if_fail (mutex);
 279
 280   if (!g_thread_supported ())
 281     return;
 282
 283   if (mutex->depth > 1)
 284     {
 285       mutex->depth--;
 286       return;
 287     }
 288   g_system_thread_assign (mutex->owner, zero_thread);
 289   g_static_mutex_unlock (&mutex->mutex);
 290 }
 291
 292 void
 293 g_static_rec_mutex_lock_full   (GStaticRecMutex *mutex,
 294                                 guint            depth)
 295 {
 296   GSystemThread self;
 297   g_return_if_fail (mutex);
 298
 299   if (!g_thread_supported ())
 300     return;
 301
 302   G_THREAD_UF (thread_self, (&self));
 303
 304   if (g_system_thread_equal (self, mutex->owner))
 305     {
 306       mutex->depth += depth;
 307       return;
 308     }
 309   g_static_mutex_lock (&mutex->mutex);
 310   g_system_thread_assign (mutex->owner, self);
 311   mutex->depth = depth;
 312 }
 313
 314 guint
 315 g_static_rec_mutex_unlock_full (GStaticRecMutex *mutex)
 316 {
 317   gint depth;
 318
 319   g_return_val_if_fail (mutex, 0);
 320
 321   if (!g_thread_supported ())
 322     return 1;
 323
 324   depth = mutex->depth;
 325
 326   g_system_thread_assign (mutex->owner, zero_thread);
 327   mutex->depth = 0;
 328   g_static_mutex_unlock (&mutex->mutex);
 329
 330   return depth;
 331 }
 332
 333 void
 334 g_static_rec_mutex_free (GStaticRecMutex *mutex)
 335 {
 336   g_return_if_fail (mutex);
 337
 338   g_static_mutex_free (&mutex->mutex);
 339 }
 340
 341 void
 342 g_static_private_init (GStaticPrivate *private_key)
 343 {
 344   private_key->index = 0;
 345 }
 346
 347 gpointer
 348 g_static_private_get (GStaticPrivate *private_key)
 349 {
 350   GRealThread *self = (GRealThread*) g_thread_self ();
 351   GArray *array;
 352
 353   array = self->private_data;
 354   if (!array)
 355     return NULL;
 356
 357   if (!private_key->index)
 358     return NULL;
 359   else if (private_key->index <= array->len)
 360     return g_array_index (array, GStaticPrivateNode,
 361                           private_key->index - 1).data;
 362   else
 363     return NULL;
 364 }
 365
 366 void
 367 g_static_private_set (GStaticPrivate *private_key,
 368                       gpointer        data,
 369                       GDestroyNotify  notify)
 370 {
 371   GRealThread *self = (GRealThread*) g_thread_self ();
 372   GArray *array;
 373   static guint next_index = 0;
 374   GStaticPrivateNode *node;
 375
 376   array = self->private_data;
 377   if (!array)
 378     {
 379       array = g_array_new (FALSE, TRUE, sizeof (GStaticPrivateNode));
 380       self->private_data = array;
 381     }
 382
 383   if (!private_key->index)
 384     {
 385       G_LOCK (g_thread);
 386
 387       if (!private_key->index)
 388         {
 389           if (g_thread_free_indeces)
 390             {
 391               private_key->index =
 392                 GPOINTER_TO_UINT (g_thread_free_indeces->data);
 393               g_thread_free_indeces =
 394                 g_slist_delete_link (g_thread_free_indeces,
 395                                      g_thread_free_indeces);
 396             }
 397           else
 398             private_key->index = ++next_index;
 399         }
 400
 401       G_UNLOCK (g_thread);
 402     }
 403
 404   if (private_key->index > array->len)
 405     g_array_set_size (array, private_key->index);
 406
 407   node = &g_array_index (array, GStaticPrivateNode, private_key->index - 1);
 408   if (node->destroy)
 409     {
 410       gpointer ddata = node->data;
 411       GDestroyNotify ddestroy = node->destroy;
 412
 413       node->data = data;
 414       node->destroy = notify;
 415
 416       ddestroy (ddata);
 417     }
 418   else
 419     {
 420       node->data = data;
 421       node->destroy = notify;
 422     }
 423 }
 424
 425 void
 426 g_static_private_free (GStaticPrivate *private_key)
 427 {
 428   guint index = private_key->index;
 429   GSList *list;
 430
 431   if (!index)
 432     return;
 433
 434   private_key->index = 0;
 435
 436   G_LOCK (g_thread);
 437   list =  g_thread_all_threads;
 438   while (list)
 439     {
 440       GRealThread *thread = list->data;
 441       GArray *array = thread->private_data;
 442       list = list->next;
 443
 444       if (array && index <= array->len)
 445         {
 446           GStaticPrivateNode *node = &g_array_index (array,
 447                                                      GStaticPrivateNode,
 448                                                      index - 1);
 449           gpointer ddata = node->data;
 450           GDestroyNotify ddestroy = node->destroy;
 451
 452           node->data = NULL;
 453           node->destroy = NULL;
 454
 455           if (ddestroy)
 456             {
 457               G_UNLOCK (g_thread);
 458               ddestroy (ddata);
 459               G_LOCK (g_thread);
 460               }
 461         }
 462     }
 463   g_thread_free_indeces = g_slist_prepend (g_thread_free_indeces,
 464                                            GUINT_TO_POINTER (index));
 465   G_UNLOCK (g_thread);
 466 }
 467
 468 void g_main_context_destroy (GMainContext *context);
 469
 470 static void
 471 g_thread_cleanup (gpointer data)
 472 {
 473   if (data)
 474     {
 475       GRealThread* thread = data;
 476       if (thread->private_data)
 477         {
 478           GArray* array = thread->private_data;
 479           guint i;
 480
 481           for (i = 0; i < array->len; i++ )
 482             {
 483               GStaticPrivateNode *node =
 484                 &g_array_index (array, GStaticPrivateNode, i);
 485               if (node->destroy)
 486                 node->destroy (node->data);
 487             }
 488           g_array_free (array, TRUE);
 489         }
 490       if (thread->context)
 491         g_main_context_destroy (thread->context);
 492
 493       /* We only free the thread structure, if it isn't joinable. If
 494          it is, the structure is freed in g_thread_join */
 495       if (!thread->thread.joinable)
 496         {
 497           G_LOCK (g_thread);
 498           g_thread_all_threads = g_slist_remove (g_thread_all_threads, data);
 499           G_UNLOCK (g_thread);
 500
 501           /* Just to make sure, this isn't used any more */
 502           g_system_thread_assign (thread->system_thread, zero_thread);
 503           g_free (thread);
 504         }
 505     }
 506 }
 507
 508 static void
 509 g_thread_fail (void)
 510 {
 511   g_error ("The thread system is not yet initialized.");
 512 }
 513
 514 static gpointer
 515 g_thread_create_proxy (gpointer data)
 516 {
 517   GRealThread* thread = data;
 518
 519   g_assert (data);
 520
 521 #ifdef G_THREAD_USE_PID_SURROGATE
 522   thread->pid = getpid ();
 523 #endif /* G_THREAD_USE_PID_SURROGATE */
 524
 525   /* This has to happen before G_LOCK, as that might call g_thread_self */
 526   g_private_set (g_thread_specific_private, data);
 527
 528   /* the lock makes sure, that thread->system_thread is written,
 529      before thread->thread.func is called. See g_thread_create. */
 530   G_LOCK (g_thread);
 531   G_UNLOCK (g_thread);
 532
 533 #ifdef G_THREAD_USE_PID_SURROGATE
 534   if (g_thread_use_default_impl)
 535     SET_PRIO (thread->pid, thread->thread.priority);
 536 #endif /* G_THREAD_USE_PID_SURROGATE */
 537
 538   thread->retval = thread->thread.func (thread->thread.data);
 539
 540   return NULL;
 541 }
 542
 543 GThread*
 544 g_thread_create_full (GThreadFunc                func,
 545                       gpointer           data,
 546                       gulong             stack_size,
 547                       gboolean           joinable,
 548                       gboolean           bound,
 549                       GThreadPriority    priority,
 550                       GError                **error)
 551 {
 552   GRealThread* result = g_new (GRealThread, 1);
 553   GError *local_error = NULL;
 554   g_return_val_if_fail (func, NULL);
 555   g_return_val_if_fail (priority >= G_THREAD_PRIORITY_LOW, NULL);
 556   g_return_val_if_fail (priority <= G_THREAD_PRIORITY_URGENT, NULL);
 557
 558   result->thread.joinable = joinable;
 559   result->thread.priority = priority;
 560   result->thread.func = func;
 561   result->thread.data = data;
 562   result->private_data = NULL;
 563   result->context = NULL;
 564   G_LOCK (g_thread);
 565   G_THREAD_UF (thread_create, (g_thread_create_proxy, result,
 566                                stack_size, joinable, bound, priority,
 567                                &result->system_thread, &local_error));
 568   g_thread_all_threads = g_slist_prepend (g_thread_all_threads, result);
 569   G_UNLOCK (g_thread);
 570
 571   if (local_error)
 572     {
 573       g_propagate_error (error, local_error);
 574       g_free (result);
 575       return NULL;
 576     }
 577
 578   return (GThread*) result;
 579 }
 580
 581 void
 582 g_thread_exit (gpointer retval)
 583 {
 584   GRealThread* real = (GRealThread*) g_thread_self ();
 585   real->retval = retval;
 586   G_THREAD_CF (thread_exit, (void)0, ());
 587 }
 588
 589 gpointer
 590 g_thread_join (GThread* thread)
 591 {
 592   GRealThread* real = (GRealThread*) thread;
 593   gpointer retval;
 594
 595   g_return_val_if_fail (thread, NULL);
 596   g_return_val_if_fail (thread->joinable, NULL);
 597   g_return_val_if_fail (!g_system_thread_equal (real->system_thread,
 598                                                 zero_thread), NULL);
 599
 600   G_THREAD_UF (thread_join, (&real->system_thread));
 601
 602   retval = real->retval;
 603
 604   G_LOCK (g_thread);
 605   g_thread_all_threads = g_slist_remove (g_thread_all_threads, thread);
 606   G_UNLOCK (g_thread);
 607
 608   /* Just to make sure, this isn't used any more */
 609   thread->joinable = 0;
 610   g_system_thread_assign (real->system_thread, zero_thread);
 611
 612   /* the thread structure for non-joinable threads is freed upon
 613      thread end. We free the memory here. This will leave a loose end,
 614      if a joinable thread is not joined. */
 615
 616   g_free (thread);
 617
 618   return retval;
 619 }
 620
 621 void
 622 g_thread_set_priority (GThread* thread,
 623                        GThreadPriority priority)
 624 {
 625   GRealThread* real = (GRealThread*) thread;
 626
 627   g_return_if_fail (thread);
 628   g_return_if_fail (!g_system_thread_equal (real->system_thread, zero_thread));
 629   g_return_if_fail (priority >= G_THREAD_PRIORITY_LOW);
 630   g_return_if_fail (priority <= G_THREAD_PRIORITY_URGENT);
 631
 632   thread->priority = priority;
 633
 634 #ifdef G_THREAD_USE_PID_SURROGATE
 635   if (g_thread_use_default_impl)
 636     SET_PRIO (real->pid, priority);
 637   else
 638 #endif /* G_THREAD_USE_PID_SURROGATE */
 639     G_THREAD_CF (thread_set_priority, (void)0,
 640                  (&real->system_thread, priority));
 641 }
 642
 643 GThread*
 644 g_thread_self (void)
 645 {
 646   GRealThread* thread = g_private_get (g_thread_specific_private);
 647
 648   if (!thread)
 649     {
 650       /* If no thread data is available, provide and set one.  This
 651          can happen for the main thread and for threads, that are not
 652          created by GLib. */
 653       thread = g_new (GRealThread, 1);
 654       thread->thread.joinable = FALSE; /* This is a save guess */
 655       thread->thread.priority = G_THREAD_PRIORITY_NORMAL; /* This is
 656                                                              just a guess */
 657       thread->thread.func = NULL;
 658       thread->thread.data = NULL;
 659       thread->private_data = NULL;
 660       thread->context = NULL;
 661
 662       if (g_thread_supported ())
 663         G_THREAD_UF (thread_self, (&thread->system_thread));
 664
 665 #ifdef G_THREAD_USE_PID_SURROGATE
 666       thread->pid = getpid ();
 667 #endif /* G_THREAD_USE_PID_SURROGATE */
 668
 669       g_private_set (g_thread_specific_private, thread);
 670
 671       G_LOCK (g_thread);
 672       g_thread_all_threads = g_slist_prepend (g_thread_all_threads, thread);
 673       G_UNLOCK (g_thread);
 674     }
 675
 676   return (GThread*)thread;
 677 }
 678
 679 void
 680 g_static_rw_lock_init (GStaticRWLock* lock)
 681 {
 682   static GStaticRWLock init_lock = G_STATIC_RW_LOCK_INIT;
 683
 684   g_return_if_fail (lock);
 685
 686   *lock = init_lock;
 687 }
 688
 689 static void inline
 690 g_static_rw_lock_wait (GCond** cond, GStaticMutex* mutex)
 691 {
 692   if (!*cond)
 693       *cond = g_cond_new ();
 694   g_cond_wait (*cond, g_static_mutex_get_mutex (mutex));
 695 }
 696
 697 static void inline
 698 g_static_rw_lock_signal (GStaticRWLock* lock)
 699 {
 700   if (lock->want_to_write && lock->write_cond)
 701     g_cond_signal (lock->write_cond);
 702   else if (lock->read_cond)
 703     g_cond_broadcast (lock->read_cond);
 704 }
 705
 706 void
 707 g_static_rw_lock_reader_lock (GStaticRWLock* lock)
 708 {
 709   g_return_if_fail (lock);
 710
 711   if (!g_threads_got_initialized)
 712     return;
 713
 714   g_static_mutex_lock (&lock->mutex);
 715   while (lock->write || lock->want_to_write)
 716     g_static_rw_lock_wait (&lock->read_cond, &lock->mutex);
 717   lock->read_counter++;
 718   g_static_mutex_unlock (&lock->mutex);
 719 }
 720
 721 gboolean
 722 g_static_rw_lock_reader_trylock (GStaticRWLock* lock)
 723 {
 724   gboolean ret_val = FALSE;
 725
 726   g_return_val_if_fail (lock, FALSE);
 727
 728   if (!g_threads_got_initialized)
 729     return TRUE;
 730
 731   g_static_mutex_lock (&lock->mutex);
 732   if (!lock->write && !lock->want_to_write)
 733     {
 734       lock->read_counter++;
 735       ret_val = TRUE;
 736     }
 737   g_static_mutex_unlock (&lock->mutex);
 738   return ret_val;
 739 }
 740
 741 void
 742 g_static_rw_lock_reader_unlock  (GStaticRWLock* lock)
 743 {
 744   g_return_if_fail (lock);
 745
 746   if (!g_threads_got_initialized)
 747     return;
 748
 749   g_static_mutex_lock (&lock->mutex);
 750   lock->read_counter--;
 751   if (lock->read_counter == 0)
 752     g_static_rw_lock_signal (lock);
 753   g_static_mutex_unlock (&lock->mutex);
 754 }
 755
 756 void
 757 g_static_rw_lock_writer_lock (GStaticRWLock* lock)
 758 {
 759   g_return_if_fail (lock);
 760
 761   if (!g_threads_got_initialized)
 762     return;
 763
 764   g_static_mutex_lock (&lock->mutex);
 765   lock->want_to_write++;
 766   while (lock->write || lock->read_counter)
 767     g_static_rw_lock_wait (&lock->write_cond, &lock->mutex);
 768   lock->want_to_write--;
 769   lock->write = TRUE;
 770   g_static_mutex_unlock (&lock->mutex);
 771 }
 772
 773 gboolean
 774 g_static_rw_lock_writer_trylock (GStaticRWLock* lock)
 775 {
 776   gboolean ret_val = FALSE;
 777
 778   g_return_val_if_fail (lock, FALSE);
 779
 780   if (!g_threads_got_initialized)
 781     return TRUE;
 782
 783   g_static_mutex_lock (&lock->mutex);
 784   if (!lock->write && !lock->read_counter)
 785     {
 786       lock->write = TRUE;
 787       ret_val = TRUE;
 788     }
 789   g_static_mutex_unlock (&lock->mutex);
 790   return ret_val;
 791 }
 792
 793 void
 794 g_static_rw_lock_writer_unlock (GStaticRWLock* lock)
 795 {
 796   g_return_if_fail (lock);
 797
 798   if (!g_threads_got_initialized)
 799     return;
 800
 801   g_static_mutex_lock (&lock->mutex);
 802   lock->write = FALSE;
 803   g_static_rw_lock_signal (lock);
 804   g_static_mutex_unlock (&lock->mutex);
 805 }
 806
 807 void
 808 g_static_rw_lock_free (GStaticRWLock* lock)
 809 {
 810   g_return_if_fail (lock);
 811
 812   if (lock->read_cond)
 813     {
 814       g_cond_free (lock->read_cond);
 815       lock->read_cond = NULL;
 816     }
 817   if (lock->write_cond)
 818     {
 819       g_cond_free (lock->write_cond);
 820       lock->write_cond = NULL;
 821     }
 822   g_static_mutex_free (&lock->mutex);
 823 }