libgc/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   GC_bool thread_blocked;
  52
  53 # ifdef CYGWIN32
  54     void *status; /* hold exit value until join in case it's a pointer */
  55     pthread_t pthread_id;
  56     short flags;                /* Protected by GC lock.        */
  57 #       define FINISHED 1       /* Thread has exited.   */
  58 #       define DETACHED 2       /* Thread is intended to be detached.   */
  59 # endif
  60 };
  61
  62 typedef volatile struct GC_thread_Rep * GC_thread;
  63
  64 /*
  65  * We generally assume that volatile ==> memory ordering, at least among
  66  * volatiles.
  67  */
  68
  69 volatile GC_bool GC_please_stop = FALSE;
  70
  71 volatile struct GC_thread_Rep thread_table[MAX_THREADS];
  72
  73 volatile LONG GC_max_thread_index = 0; /* Largest index in thread_table */
  74                                        /* that was ever used.           */
  75
  76 extern LONG WINAPI GC_write_fault_handler(struct _EXCEPTION_POINTERS *exc_info);
  77
  78 int GC_thread_is_registered (void)
  79 {
  80 #if defined(GC_DLL) || defined(GC_INSIDE_DLL)
  81         /* Registered by DllMain */
  82         return 1;
  83 #else
  84         /* FIXME: */
  85         return 0;
  86 #endif
  87 }
  88
  89 void GC_allow_register_threads (void)
  90 {
  91     /* No-op for GC pre-v7. */
  92 }
  93
  94 int GC_register_my_thread (struct GC_stack_base *sb)
  95 {
  96 #   if defined(GC_DLL) || defined(GC_INSIDE_DLL)
  97         /* Registered by DllMain. */
  98         return GC_DUPLICATE;
  99 #   else
 100         /* TODO: Implement. */
 101         return GC_UNIMPLEMENTED;
 102 #   endif
 103 }
 104
 105 void GC_register_altstack (void *stack, int stack_size, void *altstack, int altstack_size)
 106 {
 107 }
 108
 109 /*
 110  * This may be called from DllMain, and hence operates under unusual
 111  * constraints.
 112  */
 113 static GC_thread GC_new_thread(void) {
 114   int i;
 115   /* It appears to be unsafe to acquire a lock here, since this */
 116   /* code is apparently not preeemptible on some systems.       */
 117   /* (This is based on complaints, not on Microsoft's official  */
 118   /* documentation, which says this should perform "only simple */
 119   /* initialization tasks".)                                    */
 120   /* Hence we make do with nonblocking synchronization.         */
 121
 122   /* The following should be a noop according to the win32      */
 123   /* documentation.  There is empirical evidence that it        */
 124   /* isn't.             - HB                                    */
 125 # if defined(MPROTECT_VDB)
 126    if (GC_incremental) SetUnhandledExceptionFilter(GC_write_fault_handler);
 127 # endif
 128                 /* cast away volatile qualifier */
 129   for (i = 0; InterlockedExchange((IE_t)&thread_table[i].in_use,1) != 0; i++) {
 130     /* Compare-and-swap would make this cleaner, but that's not         */
 131     /* supported before Windows 98 and NT 4.0.  In Windows 2000,        */
 132     /* InterlockedExchange is supposed to be replaced by                */
 133     /* InterlockedExchangePointer, but that's not really what I         */
 134     /* want here.                                                       */
 135     if (i == MAX_THREADS - 1)
 136       ABORT("too many threads");
 137   }
 138   /* Update GC_max_thread_index if necessary.  The following is safe,   */
 139   /* and unlike CompareExchange-based solutions seems to work on all    */
 140   /* Windows95 and later platforms.                                     */
 141   /* Unfortunately, GC_max_thread_index may be temporarily out of       */
 142   /* bounds, so readers have to compensate.                             */
 143   while (i > GC_max_thread_index) {
 144     InterlockedIncrement((IE_t)&GC_max_thread_index);
 145   }
 146   if (GC_max_thread_index >= MAX_THREADS) {
 147     /* We overshot due to simultaneous increments.      */
 148     /* Setting it to MAX_THREADS-1 is always safe.      */
 149     GC_max_thread_index = MAX_THREADS - 1;
 150   }
 151
 152 # ifdef CYGWIN32
 153     thread_table[i].pthread_id = pthread_self();
 154 # endif
 155   if (!DuplicateHandle(GetCurrentProcess(),
 156                        GetCurrentThread(),
 157                        GetCurrentProcess(),
 158                        (HANDLE*)&thread_table[i].handle,
 159                        0,
 160                        0,
 161                        DUPLICATE_SAME_ACCESS)) {
 162         DWORD last_error = GetLastError();
 163         GC_printf1("Last error code: %lx\n", last_error);
 164         ABORT("DuplicateHandle failed");
 165   }
 166   thread_table[i].stack_base = GC_get_stack_base();
 167   /* Up until this point, GC_push_all_stacks considers this thread      */
 168   /* invalid.                                                           */
 169   if (thread_table[i].stack_base == NULL)
 170     ABORT("Failed to find stack base in GC_new_thread");
 171   /* Up until this point, this entry is viewed as reserved but invalid  */
 172   /* by GC_delete_thread.                                               */
 173   thread_table[i].id = GetCurrentThreadId();
 174   /* If this thread is being created while we are trying to stop        */
 175   /* the world, wait here.  Hopefully this can't happen on any  */
 176   /* systems that don't allow us to block here.                 */
 177   while (GC_please_stop) Sleep(20);
 178   GC_ASSERT(!thread_table[i]->thread_blocked);
 179   return thread_table + i;
 180 }
 181
 182 /*
 183  * GC_max_thread_index may temporarily be larger than MAX_THREADS.
 184  * To avoid subscript errors, we check on access.
 185  */
 186 #ifdef __GNUC__
 187 __inline__
 188 #endif
 189 static LONG GC_get_max_thread_index()
 190 {
 191   LONG my_max = GC_max_thread_index;
 192
 193   if (my_max >= MAX_THREADS) return MAX_THREADS-1;
 194   return my_max;
 195 }
 196
 197 /* This is intended to be lock-free, though that                        */
 198 /* assumes that the CloseHandle becomes visible before the              */
 199 /* in_use assignment.                                                   */
 200 static void GC_delete_gc_thread(GC_thread thr)
 201 {
 202     CloseHandle(thr->handle);
 203       /* cast away volatile qualifier */
 204     thr->stack_base = 0;
 205     thr->id = 0;
 206 #   ifdef CYGWIN32
 207       thr->pthread_id = 0;
 208 #   endif /* CYGWIN32 */
 209     thr->in_use = FALSE;
 210 }
 211
 212 static void GC_delete_thread(DWORD thread_id) {
 213   int i;
 214   LONG my_max = GC_get_max_thread_index();
 215
 216   for (i = 0;
 217        i <= my_max &&
 218        (!thread_table[i].in_use || thread_table[i].id != thread_id);
 219        /* Must still be in_use, since nobody else can store our thread_id. */
 220        i++) {}
 221   if (i > my_max) {
 222     WARN("Removing nonexistent thread %ld\n", (GC_word)thread_id);
 223   } else {
 224     GC_delete_gc_thread(thread_table+i);
 225   }
 226 }
 227
 228 #ifdef CYGWIN32
 229
 230 /* Return a GC_thread corresponding to a given pthread_t.       */
 231 /* Returns 0 if it's not there.                                 */
 232 /* We assume that this is only called for pthread ids that      */
 233 /* have not yet terminated or are still joinable.               */
 234 static GC_thread GC_lookup_thread(pthread_t id)
 235 {
 236   int i;
 237   LONG my_max = GC_get_max_thread_index();
 238
 239   for (i = 0;
 240        i <= my_max &&
 241        (!thread_table[i].in_use || thread_table[i].pthread_id != id
 242         || !thread_table[i].in_use);
 243        /* Must still be in_use, since nobody else can store our thread_id. */
 244        i++);
 245   if (i > my_max) return 0;
 246   return thread_table + i;
 247 }
 248
 249 #else
 250
 251 static GC_thread GC_lookup_thread(DWORD id)
 252 {
 253   int i;
 254   LONG max = GC_get_max_thread_index();
 255
 256   for (i = 0; i <= max; i++)
 257     if (thread_table[i].in_use && thread_table[i].id == id)
 258       return &thread_table[i];
 259
 260   return NULL;
 261 }
 262
 263 #endif /* CYGWIN32 */
 264
 265 void GC_push_thread_structures GC_PROTO((void))
 266 {
 267     /* Unlike the other threads implementations, the thread table here  */
 268     /* contains no pointers to the collectable heap.  Thus we have      */
 269     /* no private structures we need to preserve.                       */
 270 # ifdef CYGWIN32
 271   { int i; /* pthreads may keep a pointer in the thread exit value */
 272     LONG my_max = GC_get_max_thread_index();
 273
 274     for (i = 0; i <= my_max; i++)
 275       if (thread_table[i].in_use)
 276         GC_push_all((ptr_t)&(thread_table[i].status),
 277                     (ptr_t)(&(thread_table[i].status)+1));
 278   }
 279 # endif
 280 }
 281
 282 /* Wrappers for functions that are likely to block for an appreciable   */
 283 /* length of time.  Must be called in pairs, if at all.                 */
 284 /* Nothing much beyond the system call itself should be executed        */
 285 /* between these.                                                       */
 286
 287 void GC_start_blocking(void) {
 288     GC_thread me;
 289     LOCK();
 290 #ifdef CYGWIN32
 291     me = GC_lookup_thread(pthread_self());
 292 #else
 293     me = GC_lookup_thread(GetCurrentThreadId());
 294 #endif
 295     me->thread_blocked = TRUE;
 296     UNLOCK();
 297 }
 298
 299 void GC_end_blocking(void) {
 300     GC_thread me;
 301     LOCK();   /* This will block if the world is stopped.       */
 302 #ifdef CYGWIN32
 303     me = GC_lookup_thread(pthread_self());
 304 #else
 305     me = GC_lookup_thread(GetCurrentThreadId());
 306 #endif
 307     me->thread_blocked = FALSE;
 308     UNLOCK();
 309 }
 310
 311 /* Defined in misc.c */
 312 extern CRITICAL_SECTION GC_write_cs;
 313
 314 void GC_stop_world()
 315 {
 316   DWORD thread_id = GetCurrentThreadId();
 317   int i;
 318
 319   if (!GC_thr_initialized) ABORT("GC_stop_world() called before GC_thr_init()");
 320
 321   GC_please_stop = TRUE;
 322 # ifndef CYGWIN32
 323     EnterCriticalSection(&GC_write_cs);
 324 # endif /* !CYGWIN32 */
 325   for (i = 0; i <= GC_get_max_thread_index(); i++)
 326     if (thread_table[i].stack_base != 0
 327         && thread_table[i].id != thread_id) {
 328       if (thread_table [i].thread_blocked)
 329         continue;
 330 #     ifdef MSWINCE
 331         /* SuspendThread will fail if thread is running kernel code */
 332         while (SuspendThread(thread_table[i].handle) == (DWORD)-1)
 333           Sleep(10);
 334 #     else
 335         /* Apparently the Windows 95 GetOpenFileName call creates       */
 336         /* a thread that does not properly get cleaned up, and          */
 337         /* SuspendThread on its descriptor may provoke a crash.         */
 338         /* This reduces the probability of that event, though it still  */
 339         /* appears there's a race here.                                 */
 340         DWORD exitCode;
 341         if (GetExitCodeThread(thread_table[i].handle,&exitCode) &&
 342             exitCode != STILL_ACTIVE) {
 343           thread_table[i].stack_base = 0; /* prevent stack from being pushed */
 344 #         ifndef CYGWIN32
 345             /* this breaks pthread_join on Cygwin, which is guaranteed to  */
 346             /* only see user pthreads                                      */
 347             thread_table[i].in_use = FALSE;
 348             CloseHandle(thread_table[i].handle);
 349 #         endif
 350           continue;
 351         }
 352         if (SuspendThread(thread_table[i].handle) == (DWORD)-1) {
 353           thread_table[i].stack_base = 0; /* prevent stack from being pushed */
 354 #         ifndef CYGWIN32
 355             /* this breaks pthread_join on Cygwin, which is guaranteed to  */
 356             /* only see user pthreads                                      */
 357             thread_table[i].in_use = FALSE;
 358             CloseHandle(thread_table[i].handle);
 359 #         endif
 360         }
 361 #     endif
 362       thread_table[i].suspended = TRUE;
 363     }
 364 # ifndef CYGWIN32
 365     LeaveCriticalSection(&GC_write_cs);
 366 # endif /* !CYGWIN32 */
 367 }
 368
 369 void GC_start_world()
 370 {
 371   DWORD thread_id = GetCurrentThreadId();
 372   int i;
 373   LONG my_max = GC_get_max_thread_index();
 374
 375   for (i = 0; i <= my_max; i++)
 376     if (thread_table[i].stack_base != 0 && thread_table[i].suspended
 377         && thread_table[i].id != thread_id) {
 378       if (ResumeThread(thread_table[i].handle) == (DWORD)-1)
 379         ABORT("ResumeThread failed");
 380       thread_table[i].suspended = FALSE;
 381     }
 382   GC_please_stop = FALSE;
 383 }
 384
 385 # ifdef _MSC_VER
 386 #   pragma warning(disable:4715)
 387 # endif
 388 ptr_t GC_current_stackbottom()
 389 {
 390   DWORD thread_id = GetCurrentThreadId();
 391   int i;
 392   LONG my_max = GC_get_max_thread_index();
 393
 394   for (i = 0; i <= my_max; i++)
 395     if (thread_table[i].stack_base && thread_table[i].id == thread_id)
 396       return thread_table[i].stack_base;
 397   ABORT("no thread table entry for current thread");
 398 }
 399 # ifdef _MSC_VER
 400 #   pragma warning(default:4715)
 401 # endif
 402
 403 # ifdef MSWINCE
 404     /* The VirtualQuery calls below won't work properly on WinCE, but   */
 405     /* since each stack is restricted to an aligned 64K region of       */
 406     /* virtual memory we can just take the next lowest multiple of 64K. */
 407 #   define GC_get_stack_min(s) \
 408         ((ptr_t)(((DWORD)(s) - 1) & 0xFFFF0000))
 409 # else
 410     static ptr_t GC_get_stack_min(ptr_t s)
 411     {
 412         ptr_t bottom;
 413         MEMORY_BASIC_INFORMATION info;
 414         VirtualQuery(s, &info, sizeof(info));
 415         do {
 416             bottom = info.BaseAddress;
 417             VirtualQuery(bottom - 1, &info, sizeof(info));
 418         } while ((info.Protect & PAGE_READWRITE)
 419                  && !(info.Protect & PAGE_GUARD));
 420         return(bottom);
 421     }
 422 # endif
 423
 424 void GC_push_all_stacks()
 425 {
 426   DWORD thread_id = GetCurrentThreadId();
 427   GC_bool found_me = FALSE;
 428   int i;
 429   int dummy;
 430   ptr_t sp, stack_min;
 431   GC_thread thread;
 432   LONG my_max = GC_get_max_thread_index();
 433
 434   for (i = 0; i <= my_max; i++) {
 435     thread = thread_table + i;
 436     if (thread -> in_use && thread -> stack_base) {
 437       if (thread -> id == thread_id) {
 438         sp = (ptr_t) &dummy;
 439         found_me = TRUE;
 440       } else {
 441         CONTEXT context;
 442         context.ContextFlags = CONTEXT_INTEGER|CONTEXT_CONTROL;
 443         if (!GetThreadContext(thread_table[i].handle, &context))
 444           ABORT("GetThreadContext failed");
 445
 446         /* Push all registers that might point into the heap.  Frame    */
 447         /* pointer registers are included in case client code was       */
 448         /* compiled with the 'omit frame pointer' optimisation.         */
 449 #       define PUSH1(reg) GC_push_one((word)context.reg)
 450 #       define PUSH2(r1,r2) PUSH1(r1), PUSH1(r2)
 451 #       define PUSH4(r1,r2,r3,r4) PUSH2(r1,r2), PUSH2(r3,r4)
 452 #       if defined(I386)
 453           PUSH4(Edi,Esi,Ebx,Edx), PUSH2(Ecx,Eax), PUSH1(Ebp);
 454           sp = (ptr_t)context.Esp;
 455 #       elif defined(X86_64)
 456           PUSH4(Rax,Rcx,Rdx,Rbx); PUSH2(Rbp, Rsi); PUSH1(Rdi);
 457           PUSH4(R8, R9, R10, R11); PUSH4(R12, R13, R14, R15);
 458           sp = (ptr_t)context.Rsp;
 459 #       elif defined(ARM32)
 460           PUSH4(R0,R1,R2,R3),PUSH4(R4,R5,R6,R7),PUSH4(R8,R9,R10,R11),PUSH1(R12);
 461           sp = (ptr_t)context.Sp;
 462 #       elif defined(SHx)
 463           PUSH4(R0,R1,R2,R3), PUSH4(R4,R5,R6,R7), PUSH4(R8,R9,R10,R11);
 464           PUSH2(R12,R13), PUSH1(R14);
 465           sp = (ptr_t)context.R15;
 466 #       elif defined(MIPS)
 467           PUSH4(IntAt,IntV0,IntV1,IntA0), PUSH4(IntA1,IntA2,IntA3,IntT0);
 468           PUSH4(IntT1,IntT2,IntT3,IntT4), PUSH4(IntT5,IntT6,IntT7,IntS0);
 469           PUSH4(IntS1,IntS2,IntS3,IntS4), PUSH4(IntS5,IntS6,IntS7,IntT8);
 470           PUSH4(IntT9,IntK0,IntK1,IntS8);
 471           sp = (ptr_t)context.IntSp;
 472 #       elif defined(PPC)
 473           PUSH4(Gpr0, Gpr3, Gpr4, Gpr5),  PUSH4(Gpr6, Gpr7, Gpr8, Gpr9);
 474           PUSH4(Gpr10,Gpr11,Gpr12,Gpr14), PUSH4(Gpr15,Gpr16,Gpr17,Gpr18);
 475           PUSH4(Gpr19,Gpr20,Gpr21,Gpr22), PUSH4(Gpr23,Gpr24,Gpr25,Gpr26);
 476           PUSH4(Gpr27,Gpr28,Gpr29,Gpr30), PUSH1(Gpr31);
 477           sp = (ptr_t)context.Gpr1;
 478 #       elif defined(ALPHA)
 479           PUSH4(IntV0,IntT0,IntT1,IntT2), PUSH4(IntT3,IntT4,IntT5,IntT6);
 480           PUSH4(IntT7,IntS0,IntS1,IntS2), PUSH4(IntS3,IntS4,IntS5,IntFp);
 481           PUSH4(IntA0,IntA1,IntA2,IntA3), PUSH4(IntA4,IntA5,IntT8,IntT9);
 482           PUSH4(IntT10,IntT11,IntT12,IntAt);
 483           sp = (ptr_t)context.IntSp;
 484 #       else
 485 #         error "architecture is not supported"
 486 #       endif
 487       }
 488
 489       stack_min = GC_get_stack_min(thread->stack_base);
 490
 491       if (sp >= stack_min && sp < thread->stack_base)
 492         GC_push_all_stack(sp, thread->stack_base);
 493       else {
 494         WARN("Thread stack pointer 0x%lx out of range, pushing everything\n",
 495              (unsigned long)sp);
 496         GC_push_all_stack(stack_min, thread->stack_base);
 497       }
 498     }
 499   }
 500   if (!found_me) ABORT("Collecting from unknown thread.");
 501 }
 502
 503 void GC_get_next_stack(char *start, char **lo, char **hi)
 504 {
 505     int i;
 506 #   define ADDR_LIMIT (char *)(-1L)
 507     char * current_min = ADDR_LIMIT;
 508     LONG my_max = GC_get_max_thread_index();
 509
 510     for (i = 0; i <= my_max; i++) {
 511         char * s = (char *)thread_table[i].stack_base;
 512
 513         if (0 != s && s > start && s < current_min) {
 514             current_min = s;
 515         }
 516     }
 517     *hi = current_min;
 518     if (current_min == ADDR_LIMIT) {
 519         *lo = ADDR_LIMIT;
 520         return;
 521     }
 522     *lo = GC_get_stack_min(current_min);
 523     if (*lo < start) *lo = start;
 524 }
 525
 526 #if !defined(CYGWIN32)
 527
 528 #if !defined(MSWINCE) && defined(GC_DLL)
 529
 530 /* We register threads from DllMain */
 531
 532 GC_API HANDLE WINAPI GC_CreateThread(
 533     LPSECURITY_ATTRIBUTES lpThreadAttributes,
 534     DWORD dwStackSize, LPTHREAD_START_ROUTINE lpStartAddress,
 535     LPVOID lpParameter, DWORD dwCreationFlags, LPDWORD lpThreadId )
 536 {
 537     return CreateThread(lpThreadAttributes, dwStackSize, lpStartAddress,
 538                         lpParameter, dwCreationFlags, lpThreadId);
 539 }
 540
 541 #else /* defined(MSWINCE) || !defined(GC_DLL))  */
 542
 543 /* We have no DllMain to take care of new threads.  Thus we     */
 544 /* must properly intercept thread creation.                     */
 545
 546 typedef struct {
 547     LPTHREAD_START_ROUTINE start;
 548     LPVOID param;
 549 } thread_args;
 550
 551 static DWORD WINAPI thread_start(LPVOID arg);
 552
 553 GC_API HANDLE WINAPI GC_CreateThread(
 554     LPSECURITY_ATTRIBUTES lpThreadAttributes,
 555     DWORD dwStackSize, LPTHREAD_START_ROUTINE lpStartAddress,
 556     LPVOID lpParameter, DWORD dwCreationFlags, LPDWORD lpThreadId )
 557 {
 558     HANDLE thread_h = NULL;
 559
 560     thread_args *args;
 561
 562     if (!GC_is_initialized) GC_init();
 563                 /* make sure GC is initialized (i.e. main thread is attached) */
 564
 565     args = GC_malloc_uncollectable(sizeof(thread_args));
 566         /* Handed off to and deallocated by child thread.       */
 567     if (0 == args) {
 568         SetLastError(ERROR_NOT_ENOUGH_MEMORY);
 569         return NULL;
 570     }
 571
 572     /* set up thread arguments */
 573         args -> start = lpStartAddress;
 574         args -> param = lpParameter;
 575
 576     thread_h = CreateThread(lpThreadAttributes,
 577                             dwStackSize, thread_start,
 578                             args, dwCreationFlags,
 579                             lpThreadId);
 580
 581     return thread_h;
 582 }
 583
 584 static DWORD WINAPI thread_start(LPVOID arg)
 585 {
 586     DWORD ret = 0;
 587     thread_args *args = (thread_args *)arg;
 588
 589     GC_new_thread();
 590
 591     /* Clear the thread entry even if we exit with an exception.        */
 592     /* This is probably pointless, since an uncaught exception is       */
 593     /* supposed to result in the process being killed.                  */
 594 #ifndef __GNUC__
 595     __try {
 596 #endif /* __GNUC__ */
 597         ret = args->start (args->param);
 598 #ifndef __GNUC__
 599     } __finally {
 600 #endif /* __GNUC__ */
 601         GC_free(args);
 602         GC_delete_thread(GetCurrentThreadId());
 603 #ifndef __GNUC__
 604     }
 605 #endif /* __GNUC__ */
 606
 607     return ret;
 608 }
 609 #endif /* !defined(MSWINCE) && !(defined(__MINGW32__) && !defined(_DLL))  */
 610
 611 #endif /* !CYGWIN32 */
 612
 613 #ifdef MSWINCE
 614
 615 typedef struct {
 616     HINSTANCE hInstance;
 617     HINSTANCE hPrevInstance;
 618     LPWSTR lpCmdLine;
 619     int nShowCmd;
 620 } main_thread_args;
 621
 622 DWORD WINAPI main_thread_start(LPVOID arg);
 623
 624 int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
 625                    LPWSTR lpCmdLine, int nShowCmd)
 626 {
 627     DWORD exit_code = 1;
 628
 629     main_thread_args args = {
 630         hInstance, hPrevInstance, lpCmdLine, nShowCmd
 631     };
 632     HANDLE thread_h;
 633     DWORD thread_id;
 634
 635     /* initialize everything */
 636     GC_init();
 637
 638     /* start the main thread */
 639     thread_h = GC_CreateThread(
 640         NULL, 0, main_thread_start, &args, 0, &thread_id);
 641
 642     if (thread_h != NULL)
 643     {
 644         WaitForSingleObject (thread_h, INFINITE);
 645         GetExitCodeThread (thread_h, &exit_code);
 646         CloseHandle (thread_h);
 647     }
 648
 649     GC_deinit();
 650     DeleteCriticalSection(&GC_allocate_ml);
 651
 652     return (int) exit_code;
 653 }
 654
 655 DWORD WINAPI main_thread_start(LPVOID arg)
 656 {
 657     main_thread_args * args = (main_thread_args *) arg;
 658
 659     return (DWORD) GC_WinMain (args->hInstance, args->hPrevInstance,
 660                                args->lpCmdLine, args->nShowCmd);
 661 }
 662
 663 # else /* !MSWINCE */
 664
 665 /* Called by GC_init() - we hold the allocation lock.   */
 666 void GC_thr_init() {
 667     if (GC_thr_initialized) return;
 668     GC_main_thread = GetCurrentThreadId();
 669     GC_thr_initialized = TRUE;
 670
 671     /* Add the initial thread, so we can stop it.       */
 672     GC_new_thread();
 673 }
 674
 675 #ifdef CYGWIN32
 676
 677 struct start_info {
 678     void *(*start_routine)(void *);
 679     void *arg;
 680     GC_bool detached;
 681 };
 682
 683 int GC_pthread_join(pthread_t pthread_id, void **retval) {
 684     int result;
 685     int i;
 686     GC_thread me;
 687
 688 #   if DEBUG_CYGWIN_THREADS
 689       GC_printf3("thread 0x%x(0x%x) is joining thread 0x%x.\n",
 690                  (int)pthread_self(), GetCurrentThreadId(), (int)pthread_id);
 691 #   endif
 692
 693     /* Thread being joined might not have registered itself yet. */
 694     /* After the join,thread id may have been recycled.          */
 695     /* FIXME: It would be better if this worked more like        */
 696     /* pthread_support.c.                                        */
 697
 698     while ((me = GC_lookup_thread(pthread_id)) == 0) Sleep(10);
 699
 700     result = pthread_join(pthread_id, retval);
 701
 702     GC_delete_gc_thread(me);
 703
 704 #   if DEBUG_CYGWIN_THREADS
 705       GC_printf3("thread 0x%x(0x%x) completed join with thread 0x%x.\n",
 706                  (int)pthread_self(), GetCurrentThreadId(), (int)pthread_id);
 707 #   endif
 708
 709     return result;
 710 }
 711
 712 /* Cygwin-pthreads calls CreateThread internally, but it's not
 713  * easily interceptible by us..
 714  *   so intercept pthread_create instead
 715  */
 716 int
 717 GC_pthread_create(pthread_t *new_thread,
 718                   const pthread_attr_t *attr,
 719                   void *(*start_routine)(void *), void *arg) {
 720     int result;
 721     struct start_info * si;
 722
 723     if (!GC_is_initialized) GC_init();
 724                 /* make sure GC is initialized (i.e. main thread is attached) */
 725
 726     /* This is otherwise saved only in an area mmapped by the thread */
 727     /* library, which isn't visible to the collector.            */
 728     si = GC_malloc_uncollectable(sizeof(struct start_info));
 729     if (0 == si) return(EAGAIN);
 730
 731     si -> start_routine = start_routine;
 732     si -> arg = arg;
 733     if (attr != 0 &&
 734         pthread_attr_getdetachstate(attr, &si->detached)
 735         == PTHREAD_CREATE_DETACHED) {
 736       si->detached = TRUE;
 737     }
 738
 739 #   if DEBUG_CYGWIN_THREADS
 740       GC_printf2("About to create a thread from 0x%x(0x%x)\n",
 741                  (int)pthread_self(), GetCurrentThreadId);
 742 #   endif
 743     result = pthread_create(new_thread, attr, GC_start_routine, si);
 744
 745     if (result) { /* failure */
 746         GC_free(si);
 747     }
 748
 749     return(result);
 750 }
 751
 752 void * GC_start_routine(void * arg)
 753 {
 754     struct start_info * si = arg;
 755     void * result;
 756     void *(*start)(void *);
 757     void *start_arg;
 758     pthread_t pthread_id;
 759     GC_thread me;
 760     GC_bool detached;
 761     int i;
 762
 763 #   if DEBUG_CYGWIN_THREADS
 764       GC_printf2("thread 0x%x(0x%x) starting...\n",(int)pthread_self(),
 765                                                    GetCurrentThreadId());
 766 #   endif
 767
 768     /* If a GC occurs before the thread is registered, that GC will     */
 769     /* ignore this thread.  That's fine, since it will block trying to  */
 770     /* acquire the allocation lock, and won't yet hold interesting      */
 771     /* pointers.                                                        */
 772     LOCK();
 773     /* We register the thread here instead of in the parent, so that    */
 774     /* we don't need to hold the allocation lock during pthread_create. */
 775     me = GC_new_thread();
 776     UNLOCK();
 777
 778     start = si -> start_routine;
 779     start_arg = si -> arg;
 780     if (si-> detached) me -> flags |= DETACHED;
 781     me -> pthread_id = pthread_id = pthread_self();
 782
 783     GC_free(si); /* was allocated uncollectable */
 784
 785     pthread_cleanup_push(GC_thread_exit_proc, (void *)me);
 786     result = (*start)(start_arg);
 787     me -> status = result;
 788     pthread_cleanup_pop(0);
 789
 790 #   if DEBUG_CYGWIN_THREADS
 791       GC_printf2("thread 0x%x(0x%x) returned from start routine.\n",
 792                  (int)pthread_self(),GetCurrentThreadId());
 793 #   endif
 794
 795     return(result);
 796 }
 797
 798 void GC_thread_exit_proc(void *arg)
 799 {
 800     GC_thread me = (GC_thread)arg;
 801     int i;
 802
 803 #   if DEBUG_CYGWIN_THREADS
 804       GC_printf2("thread 0x%x(0x%x) called pthread_exit().\n",
 805                  (int)pthread_self(),GetCurrentThreadId());
 806 #   endif
 807
 808     LOCK();
 809     if (me -> flags & DETACHED) {
 810       GC_delete_thread(GetCurrentThreadId());
 811     } else {
 812       /* deallocate it as part of join */
 813       me -> flags |= FINISHED;
 814     }
 815     UNLOCK();
 816 }
 817
 818 /* nothing required here... */
 819 int GC_pthread_sigmask(int how, const sigset_t *set, sigset_t *oset) {
 820   return pthread_sigmask(how, set, oset);
 821 }
 822
 823 int GC_pthread_detach(pthread_t thread)
 824 {
 825     int result;
 826     GC_thread thread_gc_id;
 827
 828     LOCK();
 829     thread_gc_id = GC_lookup_thread(thread);
 830     UNLOCK();
 831     result = pthread_detach(thread);
 832     if (result == 0) {
 833       LOCK();
 834       thread_gc_id -> flags |= DETACHED;
 835       /* Here the pthread thread id may have been recycled. */
 836       if (thread_gc_id -> flags & FINISHED) {
 837         GC_delete_gc_thread(thread_gc_id);
 838       }
 839       UNLOCK();
 840     }
 841     return result;
 842 }
 843
 844 #else /* !CYGWIN32 */
 845
 846 /*
 847  * We avoid acquiring locks here, since this doesn't seem to be preemptable.
 848  * Pontus Rydin suggests wrapping the thread start routine instead.
 849  */
 850 #if defined(GC_DLL) || defined(GC_INSIDE_DLL)
 851 BOOL WINAPI GC_DllMain(HINSTANCE inst, ULONG reason, LPVOID reserved)
 852 {
 853   switch (reason) {
 854   case DLL_PROCESS_ATTACH:
 855     GC_init();  /* Force initialization before thread attach.   */
 856     /* fall through */
 857   case DLL_THREAD_ATTACH:
 858     GC_ASSERT(GC_thr_initialized);
 859     if (GC_main_thread != GetCurrentThreadId()) {
 860         GC_new_thread();
 861     } /* o.w. we already did it during GC_thr_init(), called by GC_init() */
 862     break;
 863
 864   case DLL_THREAD_DETACH:
 865     GC_delete_thread(GetCurrentThreadId());
 866     break;
 867
 868   case DLL_PROCESS_DETACH:
 869     {
 870       int i;
 871
 872       LOCK();
 873       for (i = 0; i <= GC_get_max_thread_index(); ++i)
 874       {
 875           if (thread_table[i].in_use)
 876             GC_delete_gc_thread(thread_table + i);
 877       }
 878       UNLOCK();
 879
 880       GC_deinit();
 881       DeleteCriticalSection(&GC_allocate_ml);
 882     }
 883     break;
 884
 885   }
 886   return TRUE;
 887 }
 888 #endif /* GC_DLL */
 889 #endif /* !CYGWIN32 */
 890
 891 # endif /* !MSWINCE */
 892
 893 #endif /* GC_WIN32_THREADS */