win32_threads.c

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#include "private/gc_priv.h"

#if defined(GC_WIN32_THREADS) 

#include <windows.h>

#ifdef CYGWIN32
# include <errno.h>

 /* Cygwin-specific forward decls */
# undef pthread_create 
# undef pthread_sigmask 
# undef pthread_join 
# undef pthread_detach
# undef dlopen 

# define DEBUG_CYGWIN_THREADS 0

  void * GC_start_routine(void * arg);
  void GC_thread_exit_proc(void *arg);

#endif

/* The type of the first argument to InterlockedExchange.	*/
/* Documented to be LONG volatile *, but at least gcc likes 	*/
/* this better.							*/
typedef LONG * IE_t;

#ifndef MAX_THREADS
# define MAX_THREADS 256
    /* FIXME:							*/
    /* Things may get quite slow for large numbers of threads,	*/
    /* since we look them up with sequential search.		*/
#endif

GC_bool GC_thr_initialized = FALSE;

DWORD GC_main_thread = 0;

struct GC_thread_Rep {
  LONG in_use; /* Updated without lock.	*/
  			/* We assert that unused 	*/
  			/* entries have invalid ids of	*/
  			/* zero and zero stack fields.  */
  DWORD id;
  HANDLE handle;
  ptr_t stack_base;	/* The cold end of the stack.   */
			/* 0 ==> entry not valid.	*/
			/* !in_use ==> stack_base == 0	*/
  GC_bool suspended;

# ifdef CYGWIN32
    void *status; /* hold exit value until join in case it's a pointer */
    pthread_t pthread_id;
    short flags;		/* Protected by GC lock.	*/
#	define FINISHED 1   	/* Thread has exited.	*/
#	define DETACHED 2	/* Thread is intended to be detached.	*/
# endif
};

typedef volatile struct GC_thread_Rep * GC_thread;

/*
 * We generally assume that volatile ==> memory ordering, at least among
 * volatiles.
 */

volatile GC_bool GC_please_stop = FALSE;

volatile struct GC_thread_Rep thread_table[MAX_THREADS];

volatile LONG GC_max_thread_index = 0; /* Largest index in thread_table	*/
				       /* that was ever used.		*/

extern LONG WINAPI GC_write_fault_handler(struct _EXCEPTION_POINTERS *exc_info);

/*
 * This may be called from DllMain, and hence operates under unusual
 * constraints.
 */
static GC_thread GC_new_thread(void) {
  int i;
  /* It appears to be unsafe to acquire a lock here, since this	*/
  /* code is apparently not preeemptible on some systems.	*/
  /* (This is based on complaints, not on Microsoft's official	*/
  /* documentation, which says this should perform "only simple	*/
  /* initialization tasks".)					*/
  /* Hence we make do with nonblocking synchronization.		*/

  /* The following should be a noop according to the win32	*/
  /* documentation.  There is empirical evidence that it	*/
  /* isn't.		- HB					*/
# if defined(MPROTECT_VDB)
   if (GC_incremental) SetUnhandledExceptionFilter(GC_write_fault_handler);
# endif
                /* cast away volatile qualifier */
  for (i = 0; InterlockedExchange((IE_t)&thread_table[i].in_use,1) != 0; i++) {
    /* Compare-and-swap would make this cleaner, but that's not 	*/
    /* supported before Windows 98 and NT 4.0.  In Windows 2000,	*/
    /* InterlockedExchange is supposed to be replaced by		*/
    /* InterlockedExchangePointer, but that's not really what I		*/
    /* want here.							*/
    if (i == MAX_THREADS - 1)
      ABORT("too many threads");
  }
  /* Update GC_max_thread_index if necessary.  The following is safe,	*/
  /* and unlike CompareExchange-based solutions seems to work on all	*/
  /* Windows95 and later platforms.					*/
  /* Unfortunately, GC_max_thread_index may be temporarily out of 	*/
  /* bounds, so readers have to compensate.				*/
  while (i > GC_max_thread_index) {
    InterlockedIncrement((IE_t)&GC_max_thread_index);
  }
  if (GC_max_thread_index >= MAX_THREADS) {
    /* We overshot due to simultaneous increments.	*/
    /* Setting it to MAX_THREADS-1 is always safe.	*/
    GC_max_thread_index = MAX_THREADS - 1;
  }
  
# ifdef CYGWIN32
    thread_table[i].pthread_id = pthread_self();
# endif
  if (!DuplicateHandle(GetCurrentProcess(),
	               GetCurrentThread(),
		       GetCurrentProcess(),
		       (HANDLE*)&thread_table[i].handle,
		       0,
		       0,
		       DUPLICATE_SAME_ACCESS)) {
	DWORD last_error = GetLastError();
	GC_printf1("Last error code: %lx\n", last_error);
	ABORT("DuplicateHandle failed");
  }
  thread_table[i].stack_base = GC_get_stack_base();
  /* Up until this point, GC_push_all_stacks considers this thread	*/
  /* invalid.								*/
  if (thread_table[i].stack_base == NULL) 
    ABORT("Failed to find stack base in GC_new_thread");
  /* Up until this point, this entry is viewed as reserved but invalid	*/
  /* by GC_delete_thread.						*/
  thread_table[i].id = GetCurrentThreadId();
  /* If this thread is being created while we are trying to stop	*/
  /* the world, wait here.  Hopefully this can't happen on any	*/
  /* systems that don't allow us to block here.			*/
  while (GC_please_stop) Sleep(20);
  return thread_table + i;
}

/*
 * GC_max_thread_index may temporarily be larger than MAX_THREADS.
 * To avoid subscript errors, we check on access.
 */
#ifdef __GNUC__
__inline__
#endif
LONG GC_get_max_thread_index()
{
  LONG my_max = GC_max_thread_index;

  if (my_max >= MAX_THREADS) return MAX_THREADS-1;
  return my_max;
}

/* This is intended to be lock-free, though that			*/
/* assumes that the CloseHandle becomes visible before the 		*/
/* in_use assignment.							*/
static void GC_delete_gc_thread(GC_thread thr)
{
    CloseHandle(thr->handle);
      /* cast away volatile qualifier */
    thr->stack_base = 0;
    thr->id = 0;
#   ifdef CYGWIN32
      thr->pthread_id = 0;
#   endif /* CYGWIN32 */
    thr->in_use = FALSE;
}

static void GC_delete_thread(DWORD thread_id) {
  int i;
  LONG my_max = GC_get_max_thread_index();

  for (i = 0;
       i <= my_max &&
       (!thread_table[i].in_use || thread_table[i].id != thread_id);
       /* Must still be in_use, since nobody else can store our thread_id. */
       i++) {}
  if (i > my_max) {
    WARN("Removing nonexistent thread %ld\n", (GC_word)thread_id);
  } else {
    GC_delete_gc_thread(thread_table+i);
  }
}


#ifdef CYGWIN32

/* Return a GC_thread corresponding to a given pthread_t.	*/
/* Returns 0 if it's not there.					*/
/* We assume that this is only called for pthread ids that	*/
/* have not yet terminated or are still joinable.		*/
static GC_thread GC_lookup_thread(pthread_t id)
{
  int i;
  LONG my_max = GC_get_max_thread_index();

  for (i = 0;
       i <= my_max &&
       (!thread_table[i].in_use || thread_table[i].pthread_id != id
	|| !thread_table[i].in_use);
       /* Must still be in_use, since nobody else can store our thread_id. */
       i++);
  if (i > my_max) return 0;
  return thread_table + i;
}

#endif /* CYGWIN32 */

void GC_push_thread_structures GC_PROTO((void))
{
    /* Unlike the other threads implementations, the thread table here	*/
    /* contains no pointers to the collectable heap.  Thus we have	*/
    /* no private structures we need to preserve.			*/
# ifdef CYGWIN32
  { int i; /* pthreads may keep a pointer in the thread exit value */
    LONG my_max = GC_get_max_thread_index();

    for (i = 0; i <= my_max; i++)
      if (thread_table[i].in_use)
	GC_push_all((ptr_t)&(thread_table[i].status),
                    (ptr_t)(&(thread_table[i].status)+1));
  }
# endif
}

/* Defined in misc.c */
extern CRITICAL_SECTION GC_write_cs;

void GC_stop_world()
{
  DWORD thread_id = GetCurrentThreadId();
  int i;

  if (!GC_thr_initialized) ABORT("GC_stop_world() called before GC_thr_init()");

  GC_please_stop = TRUE;
# ifndef CYGWIN32
    EnterCriticalSection(&GC_write_cs);
# endif /* !CYGWIN32 */
  for (i = 0; i <= GC_get_max_thread_index(); i++)
    if (thread_table[i].stack_base != 0
	&& thread_table[i].id != thread_id) {
#     ifdef MSWINCE
        /* SuspendThread will fail if thread is running kernel code */
	while (SuspendThread(thread_table[i].handle) == (DWORD)-1)
	  Sleep(10);
#     else
	/* Apparently the Windows 95 GetOpenFileName call creates	*/
	/* a thread that does not properly get cleaned up, and		*/
	/* SuspendThread on its descriptor may provoke a crash.		*/
	/* This reduces the probability of that event, though it still	*/
	/* appears there's a race here.					*/
	DWORD exitCode; 
	if (GetExitCodeThread(thread_table[i].handle,&exitCode) &&
            exitCode != STILL_ACTIVE) {
          thread_table[i].stack_base = 0; /* prevent stack from being pushed */
#         ifndef CYGWIN32
            /* this breaks pthread_join on Cygwin, which is guaranteed to  */
	    /* only see user pthreads 					   */
	    thread_table[i].in_use = FALSE;
	    CloseHandle(thread_table[i].handle);
#         endif
	  continue;
	}
	if (SuspendThread(thread_table[i].handle) == (DWORD)-1)
	  ABORT("SuspendThread failed");
#     endif
      thread_table[i].suspended = TRUE;
    }
# ifndef CYGWIN32
    LeaveCriticalSection(&GC_write_cs);
# endif /* !CYGWIN32 */
}

void GC_start_world()
{
  DWORD thread_id = GetCurrentThreadId();
  int i;
  LONG my_max = GC_get_max_thread_index();

  for (i = 0; i <= my_max; i++)
    if (thread_table[i].stack_base != 0 && thread_table[i].suspended
	&& thread_table[i].id != thread_id) {
      if (ResumeThread(thread_table[i].handle) == (DWORD)-1)
	ABORT("ResumeThread failed");
      thread_table[i].suspended = FALSE;
    }
  GC_please_stop = FALSE;
}

# ifdef _MSC_VER
#   pragma warning(disable:4715)
# endif
ptr_t GC_current_stackbottom()
{
  DWORD thread_id = GetCurrentThreadId();
  int i;
  LONG my_max = GC_get_max_thread_index();

  for (i = 0; i <= my_max; i++)
    if (thread_table[i].stack_base && thread_table[i].id == thread_id)
      return thread_table[i].stack_base;
  ABORT("no thread table entry for current thread");
}
# ifdef _MSC_VER
#   pragma warning(default:4715)
# endif

# ifdef MSWINCE
    /* The VirtualQuery calls below won't work properly on WinCE, but	*/
    /* since each stack is restricted to an aligned 64K region of	*/
    /* virtual memory we can just take the next lowest multiple of 64K.	*/
#   define GC_get_stack_min(s) \
        ((ptr_t)(((DWORD)(s) - 1) & 0xFFFF0000))
# else
    static ptr_t GC_get_stack_min(ptr_t s)
    {
	ptr_t bottom;
	MEMORY_BASIC_INFORMATION info;
	VirtualQuery(s, &info, sizeof(info));
	do {
	    bottom = info.BaseAddress;
	    VirtualQuery(bottom - 1, &info, sizeof(info));
	} while ((info.Protect & PAGE_READWRITE)
		 && !(info.Protect & PAGE_GUARD));
	return(bottom);
    }
# endif

void GC_push_all_stacks()
{
  DWORD thread_id = GetCurrentThreadId();
  GC_bool found_me = FALSE;
  int i;
  int dummy;
  ptr_t sp, stack_min;
  GC_thread thread;
  LONG my_max = GC_get_max_thread_index();
  
  for (i = 0; i <= my_max; i++) {
    thread = thread_table + i;
    if (thread -> in_use && thread -> stack_base) {
      if (thread -> id == thread_id) {
	sp = (ptr_t) &dummy;
	found_me = TRUE;
      } else {
        CONTEXT context;
        context.ContextFlags = CONTEXT_INTEGER|CONTEXT_CONTROL;
        if (!GetThreadContext(thread_table[i].handle, &context))
	  ABORT("GetThreadContext failed");

        /* Push all registers that might point into the heap.  Frame	*/
        /* pointer registers are included in case client code was	*/
        /* compiled with the 'omit frame pointer' optimisation.		*/
#       define PUSH1(reg) GC_push_one((word)context.reg)
#       define PUSH2(r1,r2) PUSH1(r1), PUSH1(r2)
#       define PUSH4(r1,r2,r3,r4) PUSH2(r1,r2), PUSH2(r3,r4)
#       if defined(I386)
          PUSH4(Edi,Esi,Ebx,Edx), PUSH2(Ecx,Eax), PUSH1(Ebp);
	  sp = (ptr_t)context.Esp;
#       elif defined(ARM32)
	  PUSH4(R0,R1,R2,R3),PUSH4(R4,R5,R6,R7),PUSH4(R8,R9,R10,R11),PUSH1(R12);
	  sp = (ptr_t)context.Sp;
#       elif defined(SHx)
	  PUSH4(R0,R1,R2,R3), PUSH4(R4,R5,R6,R7), PUSH4(R8,R9,R10,R11);
	  PUSH2(R12,R13), PUSH1(R14);
	  sp = (ptr_t)context.R15;
#       elif defined(MIPS)
	  PUSH4(IntAt,IntV0,IntV1,IntA0), PUSH4(IntA1,IntA2,IntA3,IntT0);
	  PUSH4(IntT1,IntT2,IntT3,IntT4), PUSH4(IntT5,IntT6,IntT7,IntS0);
	  PUSH4(IntS1,IntS2,IntS3,IntS4), PUSH4(IntS5,IntS6,IntS7,IntT8);
	  PUSH4(IntT9,IntK0,IntK1,IntS8);
	  sp = (ptr_t)context.IntSp;
#       elif defined(PPC)
	  PUSH4(Gpr0, Gpr3, Gpr4, Gpr5),  PUSH4(Gpr6, Gpr7, Gpr8, Gpr9);
	  PUSH4(Gpr10,Gpr11,Gpr12,Gpr14), PUSH4(Gpr15,Gpr16,Gpr17,Gpr18);
	  PUSH4(Gpr19,Gpr20,Gpr21,Gpr22), PUSH4(Gpr23,Gpr24,Gpr25,Gpr26);
	  PUSH4(Gpr27,Gpr28,Gpr29,Gpr30), PUSH1(Gpr31);
	  sp = (ptr_t)context.Gpr1;
#       elif defined(ALPHA)
	  PUSH4(IntV0,IntT0,IntT1,IntT2), PUSH4(IntT3,IntT4,IntT5,IntT6);
	  PUSH4(IntT7,IntS0,IntS1,IntS2), PUSH4(IntS3,IntS4,IntS5,IntFp);
	  PUSH4(IntA0,IntA1,IntA2,IntA3), PUSH4(IntA4,IntA5,IntT8,IntT9);
	  PUSH4(IntT10,IntT11,IntT12,IntAt);
	  sp = (ptr_t)context.IntSp;
#       else
#         error "architecture is not supported"
#       endif
      }

      stack_min = GC_get_stack_min(thread->stack_base);

      if (sp >= stack_min && sp < thread->stack_base)