boehm-gc/win32_threads.c

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