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