src/msw/thread.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        thread.cpp
   3 // Purpose:     wxThread Implementation
   4 // Author:      Original from Wolfram Gloger/Guilhem Lavaux
   5 // Modified by: Vadim Zeitlin to make it work :-)
   6 // Created:     04/22/98
   7 // RCS-ID:      $Id$
   8 // Copyright:   (c) Wolfram Gloger (1996, 1997); Guilhem Lavaux (1998),
   9 //                  Vadim Zeitlin (1999)
  10 // Licence:     wxWindows licence
  11 /////////////////////////////////////////////////////////////////////////////
  12
  13 #ifdef __GNUG__
  14     #pragma implementation "thread.h"
  15 #endif
  16
  17 // ----------------------------------------------------------------------------
  18 // headers
  19 // ----------------------------------------------------------------------------
  20
  21 // For compilers that support precompilation, includes "wx.h".
  22 #include "wx/wxprec.h"
  23
  24 #if defined(__BORLANDC__)
  25     #pragma hdrstop
  26 #endif
  27
  28 #ifndef WX_PRECOMP
  29     #include "wx/wx.h"
  30 #endif
  31
  32 #if wxUSE_THREADS
  33
  34 #include <stdio.h>
  35
  36 #include <windows.h>
  37
  38 #include "wx/module.h"
  39 #include "wx/thread.h"
  40
  41 // the possible states of the thread ("=>" shows all possible transitions from
  42 // this state)
  43 enum wxThreadState
  44 {
  45     STATE_NEW,          // didn't start execution yet (=> RUNNING)
  46     STATE_RUNNING,      // thread is running (=> PAUSED, CANCELED)
  47     STATE_PAUSED,       // thread is temporarily suspended (=> RUNNING)
  48     STATE_CANCELED,     // thread should terminate a.s.a.p. (=> EXITED)
  49     STATE_EXITED        // thread is terminating
  50 };
  51
  52 // ----------------------------------------------------------------------------
  53 // static variables
  54 // ----------------------------------------------------------------------------
  55
  56 // TLS index of the slot where we store the pointer to the current thread
  57 static DWORD s_tlsThisThread = 0xFFFFFFFF;
  58
  59 // id of the main thread - the one which can call GUI functions without first
  60 // calling wxMutexGuiEnter()
  61 static DWORD s_idMainThread = 0;
  62
  63 // if it's FALSE, some secondary thread is holding the GUI lock
  64 static bool s_bGuiOwnedByMainThread = TRUE;
  65
  66 // critical section which controls access to all GUI functions: any secondary
  67 // thread (i.e. except the main one) must enter this crit section before doing
  68 // any GUI calls
  69 static wxCriticalSection *s_critsectGui = NULL;
  70
  71 // critical section which protects s_nWaitingForGui variable
  72 static wxCriticalSection *s_critsectWaitingForGui = NULL;
  73
  74 // number of threads waiting for GUI in wxMutexGuiEnter()
  75 static size_t s_nWaitingForGui = 0;
  76
  77 // are we waiting for a thread termination?
  78 static bool s_waitingForThread = FALSE;
  79
  80 // ============================================================================
  81 // Windows implementation of thread classes
  82 // ============================================================================
  83
  84 // ----------------------------------------------------------------------------
  85 // wxMutex implementation
  86 // ----------------------------------------------------------------------------
  87 class wxMutexInternal
  88 {
  89 public:
  90     HANDLE p_mutex;
  91 };
  92
  93 wxMutex::wxMutex()
  94 {
  95     p_internal = new wxMutexInternal;
  96     p_internal->p_mutex = CreateMutex(NULL, FALSE, NULL);
  97     if ( !p_internal->p_mutex )
  98     {
  99         wxLogSysError(_("Can not create mutex."));
 100     }
 101
 102     m_locked = 0;
 103 }
 104
 105 wxMutex::~wxMutex()
 106 {
 107     if (m_locked > 0)
 108         wxLogDebug("Warning: freeing a locked mutex (%d locks).", m_locked);
 109     CloseHandle(p_internal->p_mutex);
 110 }
 111
 112 wxMutexError wxMutex::Lock()
 113 {
 114     DWORD ret;
 115
 116     ret = WaitForSingleObject(p_internal->p_mutex, INFINITE);
 117     switch ( ret )
 118     {
 119         case WAIT_ABANDONED:
 120             return wxMUTEX_BUSY;
 121
 122         case WAIT_OBJECT_0:
 123             // ok
 124             break;
 125
 126         case WAIT_FAILED:
 127             wxLogSysError(_("Couldn't acquire a mutex lock"));
 128             return wxMUTEX_MISC_ERROR;
 129
 130         case WAIT_TIMEOUT:
 131         default:
 132             wxFAIL_MSG("impossible return value in wxMutex::Lock");
 133     }
 134
 135     m_locked++;
 136     return wxMUTEX_NO_ERROR;
 137 }
 138
 139 wxMutexError wxMutex::TryLock()
 140 {
 141     DWORD ret;
 142
 143     ret = WaitForSingleObject(p_internal->p_mutex, 0);
 144     if (ret == WAIT_TIMEOUT || ret == WAIT_ABANDONED)
 145         return wxMUTEX_BUSY;
 146
 147     m_locked++;
 148     return wxMUTEX_NO_ERROR;
 149 }
 150
 151 wxMutexError wxMutex::Unlock()
 152 {
 153     if (m_locked > 0)
 154         m_locked--;
 155
 156     BOOL ret = ReleaseMutex(p_internal->p_mutex);
 157     if ( ret == 0 )
 158     {
 159         wxLogSysError(_("Couldn't release a mutex"));
 160         return wxMUTEX_MISC_ERROR;
 161     }
 162
 163     return wxMUTEX_NO_ERROR;
 164 }
 165
 166 // ----------------------------------------------------------------------------
 167 // wxCondition implementation
 168 // ----------------------------------------------------------------------------
 169
 170 class wxConditionInternal
 171 {
 172 public:
 173     HANDLE event;
 174     int waiters;
 175 };
 176
 177 wxCondition::wxCondition()
 178 {
 179     p_internal = new wxConditionInternal;
 180     p_internal->event = CreateEvent(NULL, FALSE, FALSE, NULL);
 181     if ( !p_internal->event )
 182     {
 183         wxLogSysError(_("Can not create event object."));
 184     }
 185
 186     p_internal->waiters = 0;
 187 }
 188
 189 wxCondition::~wxCondition()
 190 {
 191     CloseHandle(p_internal->event);
 192 }
 193
 194 void wxCondition::Wait(wxMutex& mutex)
 195 {
 196     mutex.Unlock();
 197     p_internal->waiters++;
 198     WaitForSingleObject(p_internal->event, INFINITE);
 199     p_internal->waiters--;
 200     mutex.Lock();
 201 }
 202
 203 bool wxCondition::Wait(wxMutex& mutex,
 204                        unsigned long sec,
 205                        unsigned long nsec)
 206 {
 207     DWORD ret;
 208
 209     mutex.Unlock();
 210     p_internal->waiters++;
 211     ret = WaitForSingleObject(p_internal->event, (sec*1000)+(nsec/1000000));
 212     p_internal->waiters--;
 213     mutex.Lock();
 214
 215     return (ret != WAIT_TIMEOUT);
 216 }
 217
 218 void wxCondition::Signal()
 219 {
 220     SetEvent(p_internal->event);
 221 }
 222
 223 void wxCondition::Broadcast()
 224 {
 225     int i;
 226
 227     for (i=0;i<p_internal->waiters;i++)
 228     {
 229         if ( SetEvent(p_internal->event) == 0 )
 230         {
 231             wxLogSysError(_("Couldn't change the state of event object."));
 232         }
 233     }
 234 }
 235
 236 // ----------------------------------------------------------------------------
 237 // wxCriticalSection implementation
 238 // ----------------------------------------------------------------------------
 239
 240 class wxCriticalSectionInternal
 241 {
 242 public:
 243     // init the critical section object
 244     wxCriticalSectionInternal()
 245         { ::InitializeCriticalSection(&m_data); }
 246
 247     // implicit cast to the associated data
 248     operator CRITICAL_SECTION *() { return &m_data; }
 249
 250     // free the associated ressources
 251     ~wxCriticalSectionInternal()
 252         { ::DeleteCriticalSection(&m_data); }
 253
 254 private:
 255     CRITICAL_SECTION m_data;
 256 };
 257
 258 wxCriticalSection::wxCriticalSection()
 259 {
 260     m_critsect = NULL;
 261 }
 262
 263 wxCriticalSection::~wxCriticalSection()
 264 {
 265     wxASSERT_MSG( !m_critsect, "Forgot to Leave() critical section" );
 266 }
 267
 268 void wxCriticalSection::Enter()
 269 {
 270     m_critsect = new wxCriticalSectionInternal;
 271
 272     ::EnterCriticalSection(*m_critsect);
 273 }
 274
 275 void wxCriticalSection::Leave()
 276 {
 277     wxCHECK_RET( m_critsect, "Leave() without matching Enter()" );
 278
 279     ::LeaveCriticalSection(*m_critsect);
 280
 281     delete m_critsect;
 282     m_critsect = NULL;
 283 }
 284
 285 // ----------------------------------------------------------------------------
 286 // wxThread implementation
 287 // ----------------------------------------------------------------------------
 288
 289 // wxThreadInternal class
 290 // ----------------------
 291
 292 class wxThreadInternal
 293 {
 294 public:
 295     wxThreadInternal()
 296     {
 297         m_hThread = 0;
 298         m_state = STATE_NEW;
 299         m_priority = WXTHREAD_DEFAULT_PRIORITY;
 300     }
 301
 302     // create a new (suspended) thread (for the given thread object)
 303     bool Create(wxThread *thread);
 304
 305     // suspend/resume/terminate
 306     bool Suspend();
 307     bool Resume();
 308     void Cancel() { m_state = STATE_CANCELED; }
 309
 310     // thread state
 311     void SetState(wxThreadState state) { m_state = state; }
 312     wxThreadState GetState() const { return m_state; }
 313
 314     // thread priority
 315     void SetPriority(unsigned int priority) { m_priority = priority; }
 316     unsigned int GetPriority() const { return m_priority; }
 317
 318     // thread handle and id
 319     HANDLE GetHandle() const { return m_hThread; }
 320     DWORD  GetId() const { return m_tid; }
 321
 322     // thread function
 323     static DWORD WinThreadStart(wxThread *thread);
 324
 325 private:
 326     HANDLE        m_hThread;    // handle of the thread
 327     wxThreadState m_state;      // state, see wxThreadState enum
 328     unsigned int  m_priority;   // thread priority in "wx" units
 329     DWORD         m_tid;        // thread id
 330 };
 331
 332 DWORD wxThreadInternal::WinThreadStart(wxThread *thread)
 333 {
 334     // store the thread object in the TLS
 335     if ( !::TlsSetValue(s_tlsThisThread, thread) )
 336     {
 337         wxLogSysError(_("Can not start thread: error writing TLS."));
 338
 339         return (DWORD)-1;
 340     }
 341
 342     DWORD ret = (DWORD)thread->Entry();
 343     thread->p_internal->SetState(STATE_EXITED);
 344     thread->OnExit();
 345
 346     delete thread;
 347
 348     return ret;
 349 }
 350
 351 bool wxThreadInternal::Create(wxThread *thread)
 352 {
 353     m_hThread = ::CreateThread
 354                   (
 355                     NULL,                               // default security
 356                     0,                                  // default stack size
 357                     (LPTHREAD_START_ROUTINE)            // thread entry point
 358                     wxThreadInternal::WinThreadStart,   //
 359                     (LPVOID)thread,                     // parameter
 360                     CREATE_SUSPENDED,                   // flags
 361                     &m_tid                              // [out] thread id
 362                   );
 363
 364     if ( m_hThread == NULL )
 365     {
 366         wxLogSysError(_("Can't create thread"));
 367
 368         return FALSE;
 369     }
 370
 371     // translate wxWindows priority to the Windows one
 372     int win_priority;
 373     if (m_priority <= 20)
 374         win_priority = THREAD_PRIORITY_LOWEST;
 375     else if (m_priority <= 40)
 376         win_priority = THREAD_PRIORITY_BELOW_NORMAL;
 377     else if (m_priority <= 60)
 378         win_priority = THREAD_PRIORITY_NORMAL;
 379     else if (m_priority <= 80)
 380         win_priority = THREAD_PRIORITY_ABOVE_NORMAL;
 381     else if (m_priority <= 100)
 382         win_priority = THREAD_PRIORITY_HIGHEST;
 383     else
 384     {
 385         wxFAIL_MSG("invalid value of thread priority parameter");
 386         win_priority = THREAD_PRIORITY_NORMAL;
 387     }
 388
 389     if ( ::SetThreadPriority(m_hThread, win_priority) == 0 )
 390     {
 391         wxLogSysError(_("Can't set thread priority"));
 392     }
 393
 394     return TRUE;
 395 }
 396
 397 bool wxThreadInternal::Suspend()
 398 {
 399     DWORD nSuspendCount = ::SuspendThread(m_hThread);
 400     if ( nSuspendCount == (DWORD)-1 )
 401     {
 402         wxLogSysError(_("Can not suspend thread %x"), m_hThread);
 403
 404         return FALSE;
 405     }
 406
 407     m_state = STATE_PAUSED;
 408
 409     return TRUE;
 410 }
 411
 412 bool wxThreadInternal::Resume()
 413 {
 414     DWORD nSuspendCount = ::ResumeThread(m_hThread);
 415     if ( nSuspendCount == (DWORD)-1 )
 416     {
 417         wxLogSysError(_("Can not resume thread %x"), m_hThread);
 418
 419         return FALSE;
 420     }
 421
 422     m_state = STATE_RUNNING;
 423
 424     return TRUE;
 425 }
 426
 427 // static functions
 428 // ----------------
 429
 430 wxThread *wxThread::This()
 431 {
 432     wxThread *thread = (wxThread *)::TlsGetValue(s_tlsThisThread);
 433
 434     // be careful, 0 may be a valid return value as well
 435     if ( !thread && (::GetLastError() != NO_ERROR) )
 436     {
 437         wxLogSysError(_("Couldn't get the current thread pointer"));
 438
 439         // return NULL...
 440     }
 441
 442     return thread;
 443 }
 444
 445 bool wxThread::IsMain()
 446 {
 447     return ::GetCurrentThreadId() == s_idMainThread;
 448 }
 449
 450 void wxThread::Yield()
 451 {
 452     // 0 argument to Sleep() is special
 453     ::Sleep(0);
 454 }
 455
 456 void wxThread::Sleep(unsigned long milliseconds)
 457 {
 458     ::Sleep(milliseconds);
 459 }
 460
 461 // create/start thread
 462 // -------------------
 463
 464 wxThreadError wxThread::Create()
 465 {
 466     if ( !p_internal->Create(this) )
 467         return wxTHREAD_NO_RESOURCE;
 468
 469     return wxTHREAD_NO_ERROR;
 470 }
 471
 472 wxThreadError wxThread::Run()
 473 {
 474     wxCriticalSectionLocker lock(m_critsect);
 475
 476     if ( p_internal->GetState() != STATE_NEW )
 477     {
 478         // actually, it may be almost any state at all, not only STATE_RUNNING
 479         return wxTHREAD_RUNNING;
 480     }
 481
 482     return Resume();
 483 }
 484
 485 // suspend/resume thread
 486 // ---------------------
 487
 488 wxThreadError wxThread::Pause()
 489 {
 490     wxCriticalSectionLocker lock(m_critsect);
 491
 492     return p_internal->Suspend() ? wxTHREAD_NO_ERROR : wxTHREAD_MISC_ERROR;
 493 }
 494
 495 wxThreadError wxThread::Resume()
 496 {
 497     wxCriticalSectionLocker lock(m_critsect);
 498
 499     return p_internal->Resume() ? wxTHREAD_NO_ERROR : wxTHREAD_MISC_ERROR;
 500 }
 501
 502 // stopping thread
 503 // ---------------
 504
 505 wxThread::ExitCode wxThread::Delete()
 506 {
 507     ExitCode rc = 0;
 508
 509     // Delete() is always safe to call, so consider all possible states
 510     if ( IsPaused() )
 511         Resume();
 512
 513     if ( IsRunning() )
 514     {
 515         if ( IsMain() )
 516         {
 517             // set flag for wxIsWaitingForThread()
 518             s_waitingForThread = TRUE;
 519
 520             wxBeginBusyCursor();
 521         }
 522
 523         HANDLE hThread;
 524         {
 525             wxCriticalSectionLocker lock(m_critsect);
 526
 527             p_internal->Cancel();
 528             hThread = p_internal->GetHandle();
 529         }
 530
 531         // we can't just wait for the thread to terminate because it might be
 532         // calling some GUI functions and so it will never terminate before we
 533         // process the Windows messages that result from these functions
 534         DWORD result;
 535         do
 536         {
 537             result = ::MsgWaitForMultipleObjects
 538                      (
 539                        1,              // number of objects to wait for
 540                        &hThread,       // the objects
 541                        FALSE,          // don't wait for all objects
 542                        INFINITE,       // no timeout
 543                        QS_ALLEVENTS    // return as soon as there are any events
 544                      );
 545
 546             switch ( result )
 547             {
 548                 case 0xFFFFFFFF:
 549                     // error
 550                     wxLogSysError(_("Can not wait for thread termination"));
 551                     Kill();
 552                     return (ExitCode)-1;
 553
 554                 case WAIT_OBJECT_0:
 555                     // thread we're waiting for terminated
 556                     break;
 557
 558                 case WAIT_OBJECT_0 + 1:
 559                     // new message arrived, process it
 560                     if ( !wxTheApp->DoMessage() )
 561                     {
 562                         // WM_QUIT received: kill the thread
 563                         Kill();
 564
 565                         return (ExitCode)-1;
 566                     }
 567
 568                     if ( IsMain() )
 569                     {
 570                         // give the thread we're waiting for chance to exit
 571                         // from the GUI call it might have been in
 572                         if ( (s_nWaitingForGui > 0) && wxGuiOwnedByMainThread() )
 573                         {
 574                             wxMutexGuiLeave();
 575                         }
 576                     }
 577
 578                     break;
 579
 580                 default:
 581                     wxFAIL_MSG("unexpected result of MsgWaitForMultipleObject");
 582             }
 583         } while ( result != WAIT_OBJECT_0 );
 584
 585         if ( IsMain() )
 586         {
 587             s_waitingForThread = FALSE;
 588
 589             wxEndBusyCursor();
 590         }
 591
 592         if ( !::GetExitCodeThread(hThread, (LPDWORD)&rc) )
 593         {
 594             wxLogLastError("GetExitCodeThread");
 595
 596             rc = (ExitCode)-1;
 597         }
 598
 599         wxASSERT_MSG( (LPVOID)rc != (LPVOID)STILL_ACTIVE,
 600                       "thread must be already terminated." );
 601
 602         ::CloseHandle(hThread);
 603     }
 604
 605     return rc;
 606 }
 607
 608 wxThreadError wxThread::Kill()
 609 {
 610     if ( !IsRunning() )
 611         return wxTHREAD_NOT_RUNNING;
 612
 613     if ( !::TerminateThread(p_internal->GetHandle(), (DWORD)-1) )
 614     {
 615         wxLogSysError(_("Couldn't terminate thread"));
 616
 617         return wxTHREAD_MISC_ERROR;
 618     }
 619
 620     delete this;
 621
 622     return wxTHREAD_NO_ERROR;
 623 }
 624
 625 void wxThread::Exit(void *status)
 626 {
 627     delete this;
 628
 629     ::ExitThread((DWORD)status);
 630
 631     wxFAIL_MSG("Couldn't return from ExitThread()!");
 632 }
 633
 634 void wxThread::SetPriority(unsigned int prio)
 635 {
 636     wxCriticalSectionLocker lock(m_critsect);
 637
 638     p_internal->SetPriority(prio);
 639 }
 640
 641 unsigned int wxThread::GetPriority() const
 642 {
 643     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 644
 645     return p_internal->GetPriority();
 646 }
 647
 648 unsigned long wxThread::GetID() const
 649 {
 650     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 651
 652     return (unsigned long)p_internal->GetId();
 653 }
 654
 655 bool wxThread::IsRunning() const
 656 {
 657     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 658
 659     return p_internal->GetState() == STATE_RUNNING;
 660 }
 661
 662 bool wxThread::IsAlive() const
 663 {
 664     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 665
 666     return (p_internal->GetState() == STATE_RUNNING) ||
 667            (p_internal->GetState() == STATE_PAUSED);
 668 }
 669
 670 bool wxThread::TestDestroy()
 671 {
 672     wxCriticalSectionLocker lock((wxCriticalSection &)m_critsect);
 673
 674     return p_internal->GetState() == STATE_CANCELED;
 675 }
 676
 677 wxThread::wxThread()
 678 {
 679     p_internal = new wxThreadInternal();
 680 }
 681
 682 wxThread::~wxThread()
 683 {
 684     delete p_internal;
 685 }
 686
 687 // ----------------------------------------------------------------------------
 688 // Automatic initialization for thread module
 689 // ----------------------------------------------------------------------------
 690
 691 class wxThreadModule : public wxModule
 692 {
 693 public:
 694     virtual bool OnInit();
 695     virtual void OnExit();
 696
 697 private:
 698     DECLARE_DYNAMIC_CLASS(wxThreadModule)
 699 };
 700
 701 IMPLEMENT_DYNAMIC_CLASS(wxThreadModule, wxModule)
 702
 703 bool wxThreadModule::OnInit()
 704 {
 705     // allocate TLS index for storing the pointer to the current thread
 706     s_tlsThisThread = ::TlsAlloc();
 707     if ( s_tlsThisThread == 0xFFFFFFFF )
 708     {
 709         // in normal circumstances it will only happen if all other
 710         // TLS_MINIMUM_AVAILABLE (>= 64) indices are already taken - in other
 711         // words, this should never happen
 712         wxLogSysError(_("Thread module initialization failed: "
 713                         "impossible to allocate index in thread "
 714                         "local storage"));
 715
 716         return FALSE;
 717     }
 718
 719     // main thread doesn't have associated wxThread object, so store 0 in the
 720     // TLS instead
 721     if ( !::TlsSetValue(s_tlsThisThread, (LPVOID)0) )
 722     {
 723         ::TlsFree(s_tlsThisThread);
 724         s_tlsThisThread = 0xFFFFFFFF;
 725
 726         wxLogSysError(_("Thread module initialization failed: "
 727                         "can not store value in thread local storage"));
 728
 729         return FALSE;
 730     }
 731
 732     s_critsectWaitingForGui = new wxCriticalSection();
 733
 734     s_critsectGui = new wxCriticalSection();
 735     s_critsectGui->Enter();
 736
 737     // no error return for GetCurrentThreadId()
 738     s_idMainThread = ::GetCurrentThreadId();
 739
 740     return TRUE;
 741 }
 742
 743 void wxThreadModule::OnExit()
 744 {
 745     if ( !::TlsFree(s_tlsThisThread) )
 746     {
 747         wxLogLastError("TlsFree failed.");
 748     }
 749
 750     if ( s_critsectGui )
 751     {
 752         s_critsectGui->Leave();
 753         delete s_critsectGui;
 754         s_critsectGui = NULL;
 755     }
 756
 757     wxDELETE(s_critsectWaitingForGui);
 758 }
 759
 760 // ----------------------------------------------------------------------------
 761 // under Windows, these functions are implemented usign a critical section and
 762 // not a mutex, so the names are a bit confusing
 763 // ----------------------------------------------------------------------------
 764
 765 void WXDLLEXPORT wxMutexGuiEnter()
 766 {
 767     // this would dead lock everything...
 768     wxASSERT_MSG( !wxThread::IsMain(),
 769                   "main thread doesn't want to block in wxMutexGuiEnter()!" );
 770
 771     // the order in which we enter the critical sections here is crucial!!
 772
 773     // set the flag telling to the main thread that we want to do some GUI
 774     {
 775         wxCriticalSectionLocker enter(*s_critsectWaitingForGui);
 776
 777         s_nWaitingForGui++;
 778     }
 779
 780     wxWakeUpMainThread();
 781
 782     // now we may block here because the main thread will soon let us in
 783     // (during the next iteration of OnIdle())
 784     s_critsectGui->Enter();
 785 }
 786
 787 void WXDLLEXPORT wxMutexGuiLeave()
 788 {
 789     wxCriticalSectionLocker enter(*s_critsectWaitingForGui);
 790
 791     if ( wxThread::IsMain() )
 792     {
 793         s_bGuiOwnedByMainThread = FALSE;
 794     }
 795     else
 796     {
 797         // decrement the number of waiters now
 798         wxASSERT_MSG( s_nWaitingForGui > 0,
 799                       "calling wxMutexGuiLeave() without entering it first?" );
 800
 801         s_nWaitingForGui--;
 802
 803         wxWakeUpMainThread();
 804     }
 805
 806     s_critsectGui->Leave();
 807 }
 808
 809 void WXDLLEXPORT wxMutexGuiLeaveOrEnter()
 810 {
 811     wxASSERT_MSG( wxThread::IsMain(),
 812                   "only main thread may call wxMutexGuiLeaveOrEnter()!" );
 813
 814     wxCriticalSectionLocker enter(*s_critsectWaitingForGui);
 815
 816     if ( s_nWaitingForGui == 0 )
 817     {
 818         // no threads are waiting for GUI - so we may acquire the lock without
 819         // any danger (but only if we don't already have it)
 820         if ( !wxGuiOwnedByMainThread() )
 821         {
 822             s_critsectGui->Enter();
 823
 824             s_bGuiOwnedByMainThread = TRUE;
 825         }
 826         //else: already have it, nothing to do
 827     }
 828     else
 829     {
 830         // some threads are waiting, release the GUI lock if we have it
 831         if ( wxGuiOwnedByMainThread() )
 832         {
 833             wxMutexGuiLeave();
 834         }
 835         //else: some other worker thread is doing GUI
 836     }
 837 }
 838
 839 bool WXDLLEXPORT wxGuiOwnedByMainThread()
 840 {
 841     return s_bGuiOwnedByMainThread;
 842 }
 843
 844 // wake up the main thread if it's in ::GetMessage()
 845 void WXDLLEXPORT wxWakeUpMainThread()
 846 {
 847     // sending any message would do - hopefully WM_NULL is harmless enough
 848     if ( !::PostThreadMessage(s_idMainThread, WM_NULL, 0, 0) )
 849     {
 850         // should never happen
 851         wxLogLastError("PostThreadMessage(WM_NULL)");
 852     }
 853 }
 854
 855 bool WXDLLEXPORT wxIsWaitingForThread()
 856 {
 857     return s_waitingForThread;
 858 }
 859
 860 #endif // wxUSE_THREADS