boehm-gc/win32_threads.c

   1 #include "private/gc_priv.h"
   2
   3 #if defined(GC_WIN32_THREADS)
   4
   5 #include <windows.h>
   6
   7 #ifdef CYGWIN32
   8 # include <errno.h>
   9
  10  /* Cygwin-specific forward decls */
  11 # undef pthread_create
  12 # undef pthread_sigmask
  13 # undef pthread_join
  14 # undef pthread_detach
  15 # undef dlopen
  16
  17 # define DEBUG_CYGWIN_THREADS 0
  18
  19   void * GC_start_routine(void * arg);
  20   void GC_thread_exit_proc(void *arg);
  21
  22 #endif
  23
  24 /* The type of the first argument to InterlockedExchange.       */
  25 /* Documented to be LONG volatile *, but at least gcc likes     */
  26 /* this better.                                                 */
  27 typedef LONG * IE_t;
  28
  29 #ifndef MAX_THREADS
  30 # define MAX_THREADS 256
  31     /* FIXME:                                                   */
  32     /* Things may get quite slow for large numbers of threads,  */
  33     /* since we look them up with sequential search.            */
  34 #endif
  35
  36 GC_bool GC_thr_initialized = FALSE;
  37
  38 DWORD GC_main_thread = 0;
  39
  40 struct GC_thread_Rep {
  41   LONG in_use; /* Updated without lock. */
  42                         /* We assert that unused        */
  43                         /* entries have invalid ids of  */
  44                         /* zero and zero stack fields.  */
  45   DWORD id;
  46   HANDLE handle;
  47   ptr_t stack_base;     /* The cold end of the stack.   */
  48                         /* 0 ==> entry not valid.       */
  49                         /* !in_use ==> stack_base == 0  */
  50   GC_bool suspended;
  51
  52 # ifdef CYGWIN32
  53     void *status; /* hold exit value until join in case it's a pointer */
  54     pthread_t pthread_id;
  55     short flags;                /* Protected by GC lock.        */
  56 #       define FINISHED 1       /* Thread has exited.   */
  57 #       define DETACHED 2       /* Thread is intended to be detached.   */
  58 # endif
  59 };
  60
  61 typedef volatile struct GC_thread_Rep * GC_thread;
  62
  63 /*
  64  * We generally assume that volatile ==> memory ordering, at least among
  65  * volatiles.
  66  */
  67
  68 volatile GC_bool GC_please_stop = FALSE;
  69
  70 volatile struct GC_thread_Rep thread_table[MAX_THREADS];
  71
  72 volatile LONG GC_max_thread_index = 0; /* Largest index in thread_table */
  73                                        /* that was ever used.           */
  74
  75 extern LONG WINAPI GC_write_fault_handler(struct _EXCEPTION_POINTERS *exc_info);
  76
  77 /*
  78  * This may be called from DllMain, and hence operates under unusual
  79  * constraints.
  80  */
  81 static GC_thread GC_new_thread(void) {
  82   int i;
  83   /* It appears to be unsafe to acquire a lock here, since this */
  84   /* code is apparently not preeemptible on some systems.       */
  85   /* (This is based on complaints, not on Microsoft's official  */
  86   /* documentation, which says this should perform "only simple */
  87   /* initialization tasks".)                                    */
  88   /* Hence we make do with nonblocking synchronization.         */
  89
  90   /* The following should be a noop according to the win32      */
  91   /* documentation.  There is empirical evidence that it        */
  92   /* isn't.             - HB                                    */
  93 # if defined(MPROTECT_VDB)
  94    if (GC_incremental) SetUnhandledExceptionFilter(GC_write_fault_handler);
  95 # endif
  96                 /* cast away volatile qualifier */
  97   for (i = 0; InterlockedExchange((IE_t)&thread_table[i].in_use,1) != 0; i++) {
  98     /* Compare-and-swap would make this cleaner, but that's not         */
  99     /* supported before Windows 98 and NT 4.0.  In Windows 2000,        */
 100     /* InterlockedExchange is supposed to be replaced by                */
 101     /* InterlockedExchangePointer, but that's not really what I         */
 102     /* want here.                                                       */
 103     if (i == MAX_THREADS - 1)
 104       ABORT("too many threads");
 105   }
 106   /* Update GC_max_thread_index if necessary.  The following is safe,   */
 107   /* and unlike CompareExchange-based solutions seems to work on all    */
 108   /* Windows95 and later platforms.                                     */
 109   /* Unfortunately, GC_max_thread_index may be temporarily out of       */
 110   /* bounds, so readers have to compensate.                             */
 111   while (i > GC_max_thread_index) {
 112     InterlockedIncrement((IE_t)&GC_max_thread_index);
 113   }
 114   if (GC_max_thread_index >= MAX_THREADS) {
 115     /* We overshot due to simultaneous increments.      */
 116     /* Setting it to MAX_THREADS-1 is always safe.      */
 117     GC_max_thread_index = MAX_THREADS - 1;
 118   }
 119
 120 # ifdef CYGWIN32
 121     thread_table[i].pthread_id = pthread_self();
 122 # endif
 123   if (!DuplicateHandle(GetCurrentProcess(),
 124                        GetCurrentThread(),
 125                        GetCurrentProcess(),
 126                        (HANDLE*)&thread_table[i].handle,
 127                        0,
 128                        0,
 129                        DUPLICATE_SAME_ACCESS)) {
 130         DWORD last_error = GetLastError();
 131         GC_printf1("Last error code: %lx\n", last_error);
 132         ABORT("DuplicateHandle failed");
 133   }
 134   thread_table[i].stack_base = GC_get_stack_base();
 135   /* Up until this point, GC_push_all_stacks considers this thread      */
 136   /* invalid.                                                           */
 137   if (thread_table[i].stack_base == NULL)
 138     ABORT("Failed to find stack base in GC_new_thread");
 139   /* Up until this point, this entry is viewed as reserved but invalid  */
 140   /* by GC_delete_thread.                                               */
 141   thread_table[i].id = GetCurrentThreadId();
 142   /* If this thread is being created while we are trying to stop        */
 143   /* the world, wait here.  Hopefully this can't happen on any  */
 144   /* systems that don't allow us to block here.                 */
 145   while (GC_please_stop) Sleep(20);
 146   return thread_table + i;
 147 }
 148
 149 /*
 150  * GC_max_thread_index may temporarily be larger than MAX_THREADS.
 151  * To avoid subscript errors, we check on access.
 152  */
 153 #ifdef __GNUC__
 154 __inline__
 155 #endif
 156 LONG GC_get_max_thread_index()
 157 {
 158   LONG my_max = GC_max_thread_index;
 159
 160   if (my_max >= MAX_THREADS) return MAX_THREADS-1;
 161   return my_max;
 162 }
 163
 164 /* This is intended to be lock-free, though that                        */
 165 /* assumes that the CloseHandle becomes visible before the              */
 166 /* in_use assignment.                                                   */
 167 static void GC_delete_gc_thread(GC_thread thr)
 168 {
 169     CloseHandle(thr->handle);
 170       /* cast away volatile qualifier */
 171     thr->stack_base = 0;
 172     thr->id = 0;
 173 #   ifdef CYGWIN32
 174       thr->pthread_id = 0;
 175 #   endif /* CYGWIN32 */
 176     thr->in_use = FALSE;
 177 }
 178
 179 static void GC_delete_thread(DWORD thread_id) {
 180   int i;
 181   LONG my_max = GC_get_max_thread_index();
 182
 183   for (i = 0;
 184        i <= my_max &&
 185        (!thread_table[i].in_use || thread_table[i].id != thread_id);
 186        /* Must still be in_use, since nobody else can store our thread_id. */
 187        i++) {}
 188   if (i > my_max) {
 189     WARN("Removing nonexistent thread %ld\n", (GC_word)thread_id);
 190   } else {
 191     GC_delete_gc_thread(thread_table+i);
 192   }
 193 }
 194
 195
 196 #ifdef CYGWIN32
 197
 198 /* Return a GC_thread corresponding to a given pthread_t.       */
 199 /* Returns 0 if it's not there.                                 */
 200 /* We assume that this is only called for pthread ids that      */
 201 /* have not yet terminated or are still joinable.               */
 202 static GC_thread GC_lookup_thread(pthread_t id)
 203 {
 204   int i;
 205   LONG my_max = GC_get_max_thread_index();
 206
 207   for (i = 0;
 208        i <= my_max &&
 209        (!thread_table[i].in_use || thread_table[i].pthread_id != id
 210         || !thread_table[i].in_use);
 211        /* Must still be in_use, since nobody else can store our thread_id. */
 212        i++);
 213   if (i > my_max) return 0;
 214   return thread_table + i;
 215 }
 216
 217 #endif /* CYGWIN32 */
 218
 219 void GC_push_thread_structures GC_PROTO((void))
 220 {
 221     /* Unlike the other threads implementations, the thread table here  */
 222     /* contains no pointers to the collectable heap.  Thus we have      */
 223     /* no private structures we need to preserve.                       */
 224 # ifdef CYGWIN32
 225   { int i; /* pthreads may keep a pointer in the thread exit value */
 226     LONG my_max = GC_get_max_thread_index();
 227
 228     for (i = 0; i <= my_max; i++)
 229       if (thread_table[i].in_use)
 230         GC_push_all((ptr_t)&(thread_table[i].status),
 231                     (ptr_t)(&(thread_table[i].status)+1));
 232   }
 233 # endif
 234 }
 235
 236 /* Defined in misc.c */
 237 extern CRITICAL_SECTION GC_write_cs;
 238
 239 void GC_stop_world()
 240 {
 241   DWORD thread_id = GetCurrentThreadId();
 242   int i;
 243
 244   if (!GC_thr_initialized) ABORT("GC_stop_world() called before GC_thr_init()");
 245
 246   GC_please_stop = TRUE;
 247 # ifndef CYGWIN32
 248     EnterCriticalSection(&GC_write_cs);
 249 # endif /* !CYGWIN32 */
 250   for (i = 0; i <= GC_get_max_thread_index(); i++)
 251     if (thread_table[i].stack_base != 0
 252         && thread_table[i].id != thread_id) {
 253 #     ifdef MSWINCE
 254         /* SuspendThread will fail if thread is running kernel code */
 255         while (SuspendThread(thread_table[i].handle) == (DWORD)-1)
 256           Sleep(10);
 257 #     else
 258         /* Apparently the Windows 95 GetOpenFileName call creates       */
 259         /* a thread that does not properly get cleaned up, and          */
 260         /* SuspendThread on its descriptor may provoke a crash.         */
 261         /* This reduces the probability of that event, though it still  */
 262         /* appears there's a race here.                                 */
 263         DWORD exitCode;
 264         if (GetExitCodeThread(thread_table[i].handle,&exitCode) &&
 265             exitCode != STILL_ACTIVE) {
 266           thread_table[i].stack_base = 0; /* prevent stack from being pushed */
 267 #         ifndef CYGWIN32
 268             /* this breaks pthread_join on Cygwin, which is guaranteed to  */
 269             /* only see user pthreads                                      */
 270             thread_table[i].in_use = FALSE;
 271             CloseHandle(thread_table[i].handle);
 272 #         endif
 273           continue;
 274         }
 275         if (SuspendThread(thread_table[i].handle) == (DWORD)-1)
 276           ABORT("SuspendThread failed");
 277 #     endif
 278       thread_table[i].suspended = TRUE;
 279     }
 280 # ifndef CYGWIN32
 281     LeaveCriticalSection(&GC_write_cs);
 282 # endif /* !CYGWIN32 */
 283 }
 284
 285 void GC_start_world()
 286 {
 287   DWORD thread_id = GetCurrentThreadId();
 288   int i;
 289   LONG my_max = GC_get_max_thread_index();
 290
 291   for (i = 0; i <= my_max; i++)
 292     if (thread_table[i].stack_base != 0 && thread_table[i].suspended
 293         && thread_table[i].id != thread_id) {
 294       if (ResumeThread(thread_table[i].handle) == (DWORD)-1)
 295         ABORT("ResumeThread failed");
 296       thread_table[i].suspended = FALSE;
 297     }
 298   GC_please_stop = FALSE;
 299 }
 300
 301 # ifdef _MSC_VER
 302 #   pragma warning(disable:4715)
 303 # endif
 304 ptr_t GC_current_stackbottom()
 305 {
 306   DWORD thread_id = GetCurrentThreadId();
 307   int i;
 308   LONG my_max = GC_get_max_thread_index();
 309
 310   for (i = 0; i <= my_max; i++)
 311     if (thread_table[i].stack_base && thread_table[i].id == thread_id)
 312       return thread_table[i].stack_base;
 313   ABORT("no thread table entry for current thread");
 314 }
 315 # ifdef _MSC_VER
 316 #   pragma warning(default:4715)
 317 # endif
 318
 319 # ifdef MSWINCE
 320     /* The VirtualQuery calls below won't work properly on WinCE, but   */
 321     /* since each stack is restricted to an aligned 64K region of       */
 322     /* virtual memory we can just take the next lowest multiple of 64K. */
 323 #   define GC_get_stack_min(s) \
 324         ((ptr_t)(((DWORD)(s) - 1) & 0xFFFF0000))
 325 # else
 326     static ptr_t GC_get_stack_min(ptr_t s)
 327     {
 328         ptr_t bottom;
 329         MEMORY_BASIC_INFORMATION info;
 330         VirtualQuery(s, &info, sizeof(info));
 331         do {
 332             bottom = info.BaseAddress;
 333             VirtualQuery(bottom - 1, &info, sizeof(info));
 334         } while ((info.Protect & PAGE_READWRITE)
 335                  && !(info.Protect & PAGE_GUARD));
 336         return(bottom);
 337     }
 338 # endif
 339
 340 void GC_push_all_stacks()
 341 {
 342   DWORD thread_id = GetCurrentThreadId();
 343   GC_bool found_me = FALSE;
 344   int i;
 345   int dummy;
 346   ptr_t sp, stack_min;
 347   GC_thread thread;
 348   LONG my_max = GC_get_max_thread_index();
 349
 350   for (i = 0; i <= my_max; i++) {
 351     thread = thread_table + i;
 352     if (thread -> in_use && thread -> stack_base) {
 353       if (thread -> id == thread_id) {
 354         sp = (ptr_t) &dummy;
 355         found_me = TRUE;
 356       } else {
 357         CONTEXT context;
 358         context.ContextFlags = CONTEXT_INTEGER|CONTEXT_CONTROL;
 359         if (!GetThreadContext(thread_table[i].handle, &context))
 360           ABORT("GetThreadContext failed");
 361
 362         /* Push all registers that might point into the heap.  Frame    */
 363         /* pointer registers are included in case client code was       */
 364         /* compiled with the 'omit frame pointer' optimisation.         */
 365 #       define PUSH1(reg) GC_push_one((word)context.reg)
 366 #       define PUSH2(r1,r2) PUSH1(r1), PUSH1(r2)
 367 #       define PUSH4(r1,r2,r3,r4) PUSH2(r1,r2), PUSH2(r3,r4)
 368 #       if defined(__x86_64__)
 369           PUSH4(Rdi,Rsi,Rbx,Rdx), PUSH2(Rcx,Rax), PUSH1(Rbp);
 370           PUSH4(R8,R9,R10,R11), PUSH4(R12,R13,R14,R15);
 371           sp = (ptr_t)context.Rsp;
 372 #       elif defined(I386)
 373           PUSH4(Edi,Esi,Ebx,Edx), PUSH2(Ecx,Eax), PUSH1(Ebp);
 374           sp = (ptr_t)context.Esp;
 375 #       elif defined(ARM32)
 376           PUSH4(R0,R1,R2,R3),PUSH4(R4,R5,R6,R7),PUSH4(R8,R9,R10,R11),PUSH1(R12);
 377           sp = (ptr_t)context.Sp;
 378 #       elif defined(SHx)
 379           PUSH4(R0,R1,R2,R3), PUSH4(R4,R5,R6,R7), PUSH4(R8,R9,R10,R11);
 380           PUSH2(R12,R13), PUSH1(R14);
 381           sp = (ptr_t)context.R15;
 382 #       elif defined(MIPS)
 383           PUSH4(IntAt,IntV0,IntV1,IntA0), PUSH4(IntA1,IntA2,IntA3,IntT0);
 384           PUSH4(IntT1,IntT2,IntT3,IntT4), PUSH4(IntT5,IntT6,IntT7,IntS0);
 385           PUSH4(IntS1,IntS2,IntS3,IntS4), PUSH4(IntS5,IntS6,IntS7,IntT8);
 386           PUSH4(IntT9,IntK0,IntK1,IntS8);
 387           sp = (ptr_t)context.IntSp;
 388 #       elif defined(PPC)
 389           PUSH4(Gpr0, Gpr3, Gpr4, Gpr5),  PUSH4(Gpr6, Gpr7, Gpr8, Gpr9);
 390           PUSH4(Gpr10,Gpr11,Gpr12,Gpr14), PUSH4(Gpr15,Gpr16,Gpr17,Gpr18);
 391           PUSH4(Gpr19,Gpr20,Gpr21,Gpr22), PUSH4(Gpr23,Gpr24,Gpr25,Gpr26);
 392           PUSH4(Gpr27,Gpr28,Gpr29,Gpr30), PUSH1(Gpr31);
 393           sp = (ptr_t)context.Gpr1;
 394 #       elif defined(ALPHA)
 395           PUSH4(IntV0,IntT0,IntT1,IntT2), PUSH4(IntT3,IntT4,IntT5,IntT6);
 396           PUSH4(IntT7,IntS0,IntS1,IntS2), PUSH4(IntS3,IntS4,IntS5,IntFp);
 397           PUSH4(IntA0,IntA1,IntA2,IntA3), PUSH4(IntA4,IntA5,IntT8,IntT9);
 398           PUSH4(IntT10,IntT11,IntT12,IntAt);
 399           sp = (ptr_t)context.IntSp;
 400 #       else
 401 #         error "architecture is not supported"
 402 #       endif
 403       }
 404
 405       stack_min = GC_get_stack_min(thread->stack_base);
 406
 407       if (sp >= stack_min && sp < thread->stack_base)
 408         GC_push_all_stack(sp, thread->stack_base);
 409       else {
 410         WARN("Thread stack pointer 0x%lx out of range, pushing everything\n",
 411              (unsigned long)sp);
 412         GC_push_all_stack(stack_min, thread->stack_base);
 413       }
 414     }
 415   }
 416   if (!found_me) ABORT("Collecting from unknown thread.");
 417 }
 418
 419 void GC_get_next_stack(char *start, char **lo, char **hi)
 420 {
 421     int i;
 422 #   define ADDR_LIMIT (char *)(-1L)
 423     char * current_min = ADDR_LIMIT;
 424     LONG my_max = GC_get_max_thread_index();
 425
 426     for (i = 0; i <= my_max; i++) {
 427         char * s = (char *)thread_table[i].stack_base;
 428
 429         if (0 != s && s > start && s < current_min) {
 430             current_min = s;
 431         }
 432     }
 433     *hi = current_min;
 434     if (current_min == ADDR_LIMIT) {
 435         *lo = ADDR_LIMIT;
 436         return;
 437     }
 438     *lo = GC_get_stack_min(current_min);
 439     if (*lo < start) *lo = start;
 440 }
 441
 442 #if !defined(CYGWIN32)
 443
 444 #if !defined(MSWINCE) && defined(GC_DLL)
 445
 446 /* We register threads from DllMain */
 447
 448 GC_API HANDLE WINAPI GC_CreateThread(
 449     LPSECURITY_ATTRIBUTES lpThreadAttributes,
 450     DWORD dwStackSize, LPTHREAD_START_ROUTINE lpStartAddress,
 451     LPVOID lpParameter, DWORD dwCreationFlags, LPDWORD lpThreadId )
 452 {
 453     return CreateThread(lpThreadAttributes, dwStackSize, lpStartAddress,
 454                         lpParameter, dwCreationFlags, lpThreadId);
 455 }
 456
 457 #else /* defined(MSWINCE) || !defined(GC_DLL))  */
 458
 459 /* We have no DllMain to take care of new threads.  Thus we     */
 460 /* must properly intercept thread creation.                     */
 461
 462 typedef struct {
 463     LPTHREAD_START_ROUTINE start;
 464     LPVOID param;
 465 } thread_args;
 466
 467 static DWORD WINAPI thread_start(LPVOID arg);
 468
 469 GC_API HANDLE WINAPI GC_CreateThread(
 470     LPSECURITY_ATTRIBUTES lpThreadAttributes,
 471     DWORD dwStackSize, LPTHREAD_START_ROUTINE lpStartAddress,
 472     LPVOID lpParameter, DWORD dwCreationFlags, LPDWORD lpThreadId )
 473 {
 474     HANDLE thread_h = NULL;
 475
 476     thread_args *args;
 477
 478     if (!GC_is_initialized) GC_init();
 479                 /* make sure GC is initialized (i.e. main thread is attached) */
 480
 481     args = GC_malloc_uncollectable(sizeof(thread_args));
 482         /* Handed off to and deallocated by child thread.       */
 483     if (0 == args) {
 484         SetLastError(ERROR_NOT_ENOUGH_MEMORY);
 485         return NULL;
 486     }
 487
 488     /* set up thread arguments */
 489         args -> start = lpStartAddress;
 490         args -> param = lpParameter;
 491
 492     thread_h = CreateThread(lpThreadAttributes,
 493                             dwStackSize, thread_start,
 494                             args, dwCreationFlags,
 495                             lpThreadId);
 496
 497     return thread_h;
 498 }
 499
 500 static DWORD WINAPI thread_start(LPVOID arg)
 501 {
 502     DWORD ret = 0;
 503     thread_args *args = (thread_args *)arg;
 504
 505     GC_new_thread();
 506
 507     /* Clear the thread entry even if we exit with an exception.        */
 508     /* This is probably pointless, since an uncaught exception is       */
 509     /* supposed to result in the process being killed.                  */
 510 #ifndef __GNUC__
 511     __try {
 512 #endif /* __GNUC__ */
 513         ret = args->start (args->param);
 514 #ifndef __GNUC__
 515     } __finally {
 516 #endif /* __GNUC__ */
 517         GC_free(args);
 518         GC_delete_thread(GetCurrentThreadId());
 519 #ifndef __GNUC__
 520     }
 521 #endif /* __GNUC__ */
 522
 523     return ret;
 524 }
 525 #endif /* !defined(MSWINCE) && !(defined(__MINGW32__) && !defined(_DLL))  */
 526
 527 #endif /* !CYGWIN32 */
 528
 529 #ifdef MSWINCE
 530
 531 typedef struct {
 532     HINSTANCE hInstance;
 533     HINSTANCE hPrevInstance;
 534     LPWSTR lpCmdLine;
 535     int nShowCmd;
 536 } main_thread_args;
 537
 538 DWORD WINAPI main_thread_start(LPVOID arg);
 539
 540 int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
 541                    LPWSTR lpCmdLine, int nShowCmd)
 542 {
 543     DWORD exit_code = 1;
 544
 545     main_thread_args args = {
 546         hInstance, hPrevInstance, lpCmdLine, nShowCmd
 547     };
 548     HANDLE thread_h;
 549     DWORD thread_id;
 550
 551     /* initialize everything */
 552     GC_init();
 553
 554     /* start the main thread */
 555     thread_h = GC_CreateThread(
 556         NULL, 0, main_thread_start, &args, 0, &thread_id);
 557
 558     if (thread_h != NULL)
 559     {
 560         WaitForSingleObject (thread_h, INFINITE);
 561         GetExitCodeThread (thread_h, &exit_code);
 562         CloseHandle (thread_h);
 563     }
 564
 565     GC_deinit();
 566     DeleteCriticalSection(&GC_allocate_ml);
 567
 568     return (int) exit_code;
 569 }
 570
 571 DWORD WINAPI main_thread_start(LPVOID arg)
 572 {
 573     main_thread_args * args = (main_thread_args *) arg;
 574
 575     return (DWORD) GC_WinMain (args->hInstance, args->hPrevInstance,
 576                                args->lpCmdLine, args->nShowCmd);
 577 }
 578
 579 # else /* !MSWINCE */
 580
 581 /* Called by GC_init() - we hold the allocation lock.   */
 582 void GC_thr_init() {
 583     if (GC_thr_initialized) return;
 584     GC_main_thread = GetCurrentThreadId();
 585     GC_thr_initialized = TRUE;
 586
 587     /* Add the initial thread, so we can stop it.       */
 588     GC_new_thread();
 589 }
 590
 591 #ifdef CYGWIN32
 592
 593 struct start_info {
 594     void *(*start_routine)(void *);
 595     void *arg;
 596     GC_bool detached;
 597 };
 598
 599 int GC_pthread_join(pthread_t pthread_id, void **retval) {
 600     int result;
 601     int i;
 602     GC_thread me;
 603
 604 #   if DEBUG_CYGWIN_THREADS
 605       GC_printf3("thread 0x%x(0x%x) is joining thread 0x%x.\n",
 606                  (int)pthread_self(), GetCurrentThreadId(), (int)pthread_id);
 607 #   endif
 608
 609     /* Thread being joined might not have registered itself yet. */
 610     /* After the join,thread id may have been recycled.          */
 611     /* FIXME: It would be better if this worked more like        */
 612     /* pthread_support.c.                                        */
 613
 614     while ((me = GC_lookup_thread(pthread_id)) == 0) Sleep(10);
 615
 616     result = pthread_join(pthread_id, retval);
 617
 618     GC_delete_gc_thread(me);
 619
 620 #   if DEBUG_CYGWIN_THREADS
 621       GC_printf3("thread 0x%x(0x%x) completed join with thread 0x%x.\n",
 622                  (int)pthread_self(), GetCurrentThreadId(), (int)pthread_id);
 623 #   endif
 624
 625     return result;
 626 }
 627
 628 /* Cygwin-pthreads calls CreateThread internally, but it's not
 629  * easily interceptible by us..
 630  *   so intercept pthread_create instead
 631  */
 632 int
 633 GC_pthread_create(pthread_t *new_thread,
 634                   const pthread_attr_t *attr,
 635                   void *(*start_routine)(void *), void *arg) {
 636     int result;
 637     struct start_info * si;
 638
 639     if (!GC_is_initialized) GC_init();
 640                 /* make sure GC is initialized (i.e. main thread is attached) */
 641
 642     /* This is otherwise saved only in an area mmapped by the thread */
 643     /* library, which isn't visible to the collector.            */
 644     si = GC_malloc_uncollectable(sizeof(struct start_info));
 645     if (0 == si) return(EAGAIN);
 646
 647     si -> start_routine = start_routine;
 648     si -> arg = arg;
 649     if (attr != 0 &&
 650         pthread_attr_getdetachstate(attr, &si->detached)
 651         == PTHREAD_CREATE_DETACHED) {
 652       si->detached = TRUE;
 653     }
 654
 655 #   if DEBUG_CYGWIN_THREADS
 656       GC_printf2("About to create a thread from 0x%x(0x%x)\n",
 657                  (int)pthread_self(), GetCurrentThreadId);
 658 #   endif
 659     result = pthread_create(new_thread, attr, GC_start_routine, si);
 660
 661     if (result) { /* failure */
 662         GC_free(si);
 663     }
 664
 665     return(result);
 666 }
 667
 668 void * GC_start_routine(void * arg)
 669 {
 670     struct start_info * si = arg;
 671     void * result;
 672     void *(*start)(void *);
 673     void *start_arg;
 674     pthread_t pthread_id;
 675     GC_thread me;
 676     GC_bool detached;
 677     int i;
 678
 679 #   if DEBUG_CYGWIN_THREADS
 680       GC_printf2("thread 0x%x(0x%x) starting...\n",(int)pthread_self(),
 681                                                    GetCurrentThreadId());
 682 #   endif
 683
 684     /* If a GC occurs before the thread is registered, that GC will     */
 685     /* ignore this thread.  That's fine, since it will block trying to  */
 686     /* acquire the allocation lock, and won't yet hold interesting      */
 687     /* pointers.                                                        */
 688     LOCK();
 689     /* We register the thread here instead of in the parent, so that    */
 690     /* we don't need to hold the allocation lock during pthread_create. */
 691     me = GC_new_thread();
 692     UNLOCK();
 693
 694     start = si -> start_routine;
 695     start_arg = si -> arg;
 696     if (si-> detached) me -> flags |= DETACHED;
 697     me -> pthread_id = pthread_id = pthread_self();
 698
 699     GC_free(si); /* was allocated uncollectable */
 700
 701     pthread_cleanup_push(GC_thread_exit_proc, (void *)me);
 702     result = (*start)(start_arg);
 703     me -> status = result;
 704     pthread_cleanup_pop(0);
 705
 706 #   if DEBUG_CYGWIN_THREADS
 707       GC_printf2("thread 0x%x(0x%x) returned from start routine.\n",
 708                  (int)pthread_self(),GetCurrentThreadId());
 709 #   endif
 710
 711     return(result);
 712 }
 713
 714 void GC_thread_exit_proc(void *arg)
 715 {
 716     GC_thread me = (GC_thread)arg;
 717     int i;
 718
 719 #   if DEBUG_CYGWIN_THREADS
 720       GC_printf2("thread 0x%x(0x%x) called pthread_exit().\n",
 721                  (int)pthread_self(),GetCurrentThreadId());
 722 #   endif
 723
 724     LOCK();
 725     if (me -> flags & DETACHED) {
 726       GC_delete_thread(GetCurrentThreadId());
 727     } else {
 728       /* deallocate it as part of join */
 729       me -> flags |= FINISHED;
 730     }
 731     UNLOCK();
 732 }
 733
 734 /* nothing required here... */
 735 int GC_pthread_sigmask(int how, const sigset_t *set, sigset_t *oset) {
 736   return pthread_sigmask(how, set, oset);
 737 }
 738
 739 int GC_pthread_detach(pthread_t thread)
 740 {
 741     int result;
 742     GC_thread thread_gc_id;
 743
 744     LOCK();
 745     thread_gc_id = GC_lookup_thread(thread);
 746     UNLOCK();
 747     result = pthread_detach(thread);
 748     if (result == 0) {
 749       LOCK();
 750       thread_gc_id -> flags |= DETACHED;
 751       /* Here the pthread thread id may have been recycled. */
 752       if (thread_gc_id -> flags & FINISHED) {
 753         GC_delete_gc_thread(thread_gc_id);
 754       }
 755       UNLOCK();
 756     }
 757     return result;
 758 }
 759
 760 GC_PTR GC_get_thread_stack_base()
 761 {
 762 #ifdef __x86_64__
 763   return ((NT_TIB*)NtCurrentTeb())->StackBase;
 764 #else
 765   extern GC_PTR _tlsbase __asm__ ("%fs:4");
 766   return _tlsbase;
 767 #endif
 768 }
 769
 770 #else /* !CYGWIN32 */
 771
 772 /*
 773  * We avoid acquiring locks here, since this doesn't seem to be preemptable.
 774  * Pontus Rydin suggests wrapping the thread start routine instead.
 775  */
 776 #ifdef GC_DLL
 777 BOOL WINAPI DllMain(HINSTANCE inst, ULONG reason, LPVOID reserved)
 778 {
 779   switch (reason) {
 780   case DLL_PROCESS_ATTACH:
 781     GC_init();  /* Force initialization before thread attach.   */
 782     /* fall through */
 783   case DLL_THREAD_ATTACH:
 784     GC_ASSERT(GC_thr_initialized);
 785     if (GC_main_thread != GetCurrentThreadId()) {
 786         GC_new_thread();
 787     } /* o.w. we already did it during GC_thr_init(), called by GC_init() */
 788     break;
 789
 790   case DLL_THREAD_DETACH:
 791     GC_delete_thread(GetCurrentThreadId());
 792     break;
 793
 794   case DLL_PROCESS_DETACH:
 795     {
 796       int i;
 797
 798       LOCK();
 799       for (i = 0; i <= GC_get_max_thread_index(); ++i)
 800       {
 801           if (thread_table[i].in_use)
 802             GC_delete_gc_thread(thread_table + i);
 803       }
 804       UNLOCK();
 805
 806       GC_deinit();
 807       DeleteCriticalSection(&GC_allocate_ml);
 808     }
 809     break;
 810
 811   }
 812   return TRUE;
 813 }
 814 #endif /* GC_DLL */
 815 #endif /* !CYGWIN32 */
 816
 817 # endif /* !MSWINCE */
 818
 819 #endif /* GC_WIN32_THREADS */