boehm-gc/darwin_stop_world.c - gcc - Git at Google

 #include "private/pthread_support.h"

 /* This probably needs more porting work to ppc64. */

 # if defined(GC_DARWIN_THREADS)

 /* From "Inside Mac OS X - Mach-O Runtime Architecture" published by Apple
    Page 49:
    "The space beneath the stack pointer, where a new stack frame would normally
    be allocated, is called the red zone. This area as shown in Figure 3-2 may
    be used for any purpose as long as a new stack frame does not need to be
    added to the stack."

    Page 50: "If a leaf procedure's red zone usage would exceed 224 bytes, then
    it must set up a stack frame just like routines that call other routines."
 */
 #if defined(__ppc__)
 # define PPC_RED_ZONE_SIZE 224
 #elif defined(__ppc64__)
 # define PPC_RED_ZONE_SIZE 320
 #endif

 typedef struct StackFrame {
   unsigned long	savedSP;
   unsigned long	savedCR;
   unsigned long	savedLR;
   unsigned long	reserved[2];
   unsigned long	savedRTOC;
 } StackFrame;

 unsigned long FindTopOfStack(unsigned long stack_start) {
   StackFrame	*frame;

   if (stack_start == 0) {
 # ifdef POWERPC
 #   if CPP_WORDSZ == 32
       __asm__ volatile("lwz	%0,0(r1)" : "=r" (frame));
 #   else
       __asm__ volatile("ld	%0,0(r1)" : "=r" (frame));
 #   endif
 # endif
   } else {
     frame = (StackFrame *)stack_start;
   }

 # ifdef DEBUG_THREADS
     /* GC_printf1("FindTopOfStack start at sp = %p\n", frame); */
 # endif
   do {
     if (frame->savedSP == 0) break;
     		/* if there are no more stack frames, stop */

     frame = (StackFrame*)frame->savedSP;

     /* we do these next two checks after going to the next frame
        because the LR for the first stack frame in the loop
        is not set up on purpose, so we shouldn't check it. */
     if ((frame->savedLR & ~3) == 0) break; /* if the next LR is bogus, stop */
     if ((~(frame->savedLR) & ~3) == 0) break; /* ditto */
   } while (1);

 # ifdef DEBUG_THREADS
     /* GC_printf1("FindTopOfStack finish at sp = %p\n", frame); */
 # endif

   return (unsigned long)frame;
 }

 #ifdef DARWIN_DONT_PARSE_STACK
 void GC_push_all_stacks() {
   int i;
   kern_return_t r;
   GC_thread p;
   pthread_t me;
   ptr_t lo, hi;
   GC_THREAD_STATE_T state;
   mach_msg_type_number_t thread_state_count = GC_MACH_THREAD_STATE_COUNT;

   me = pthread_self();
   if (!GC_thr_initialized) GC_thr_init();

   for(i=0;i<THREAD_TABLE_SZ;i++) {
     for(p=GC_threads[i];p!=0;p=p->next) {
       if(p -> flags & FINISHED) continue;
       if(pthread_equal(p->id,me)) {
 	lo = GC_approx_sp();
       } else {
 	/* Get the thread state (registers, etc) */
 	r = thread_get_state(p->stop_info.mach_thread, GC_MACH_THREAD_STATE,
 			     (natural_t*)&state, &thread_state_count);
 	if(r != KERN_SUCCESS) ABORT("thread_get_state failed");

 #if defined(I386)
 	lo = (void*)state . THREAD_FLD (esp);

 	GC_push_one(state . THREAD_FLD (eax));
 	GC_push_one(state . THREAD_FLD (ebx));
 	GC_push_one(state . THREAD_FLD (ecx));
 	GC_push_one(state . THREAD_FLD (edx));
 	GC_push_one(state . THREAD_FLD (edi));
 	GC_push_one(state . THREAD_FLD (esi));
 	GC_push_one(state . THREAD_FLD (ebp));

 #elif defined(X86_64)
 	lo = (void*)state . THREAD_FLD (rsp);

 	GC_push_one(state . THREAD_FLD (rax));
 	GC_push_one(state . THREAD_FLD (rbx));
 	GC_push_one(state . THREAD_FLD (rcx));
 	GC_push_one(state . THREAD_FLD (rdx));
 	GC_push_one(state . THREAD_FLD (rdi));
 	GC_push_one(state . THREAD_FLD (rsi));
 	GC_push_one(state . THREAD_FLD (rbp));
 	GC_push_one(state . THREAD_FLD (rsp));
 	GC_push_one(state . THREAD_FLD (r8));
 	GC_push_one(state . THREAD_FLD (r9));
 	GC_push_one(state . THREAD_FLD (r10));
 	GC_push_one(state . THREAD_FLD (r11));
 	GC_push_one(state . THREAD_FLD (r12));
 	GC_push_one(state . THREAD_FLD (r13));
 	GC_push_one(state . THREAD_FLD (r14));
 	GC_push_one(state . THREAD_FLD (r15));
 	GC_push_one(state . THREAD_FLD (rip));
 	GC_push_one(state . THREAD_FLD (rflags));
 	GC_push_one(state . THREAD_FLD (cs));
 	GC_push_one(state . THREAD_FLD (fs));
 	GC_push_one(state . THREAD_FLD (gs));

 #elif defined(POWERPC)
 	lo = (void*)(state . THREAD_FLD (r1) - PPC_RED_ZONE_SIZE);

 	GC_push_one(state . THREAD_FLD (r0));
 	GC_push_one(state . THREAD_FLD (r2));
 	GC_push_one(state . THREAD_FLD (r3));
 	GC_push_one(state . THREAD_FLD (r4));
 	GC_push_one(state . THREAD_FLD (r5));
 	GC_push_one(state . THREAD_FLD (r6));
 	GC_push_one(state . THREAD_FLD (r7));
 	GC_push_one(state . THREAD_FLD (r8));
 	GC_push_one(state . THREAD_FLD (r9));
 	GC_push_one(state . THREAD_FLD (r10));
 	GC_push_one(state . THREAD_FLD (r11));
 	GC_push_one(state . THREAD_FLD (r12));
 	GC_push_one(state . THREAD_FLD (r13));
 	GC_push_one(state . THREAD_FLD (r14));
 	GC_push_one(state . THREAD_FLD (r15));
 	GC_push_one(state . THREAD_FLD (r16));
 	GC_push_one(state . THREAD_FLD (r17));
 	GC_push_one(state . THREAD_FLD (r18));
 	GC_push_one(state . THREAD_FLD (r19));
 	GC_push_one(state . THREAD_FLD (r20));
 	GC_push_one(state . THREAD_FLD (r21));
 	GC_push_one(state . THREAD_FLD (r22));
 	GC_push_one(state . THREAD_FLD (r23));
 	GC_push_one(state . THREAD_FLD (r24));
 	GC_push_one(state . THREAD_FLD (r25));
 	GC_push_one(state . THREAD_FLD (r26));
 	GC_push_one(state . THREAD_FLD (r27));
 	GC_push_one(state . THREAD_FLD (r28));
 	GC_push_one(state . THREAD_FLD (r29));
 	GC_push_one(state . THREAD_FLD (r30));
 	GC_push_one(state . THREAD_FLD (r31));
 #else
 # error FIXME for non-x86 || ppc architectures
 #endif
       } /* p != me */
       if(p->flags & MAIN_THREAD)
 	hi = GC_stackbottom;
       else
 	hi = p->stack_end;
 #if DEBUG_THREADS
       GC_printf3("Darwin: Stack for thread 0x%lx = [%lx,%lx)\n",
 		 (unsigned long) p -> id,
 		 (unsigned long) lo,
 		 (unsigned long) hi
 		 );
 #endif
       GC_push_all_stack(lo,hi);
     } /* for(p=GC_threads[i]...) */
   } /* for(i=0;i<THREAD_TABLE_SZ...) */
 }

 #else /* !DARWIN_DONT_PARSE_STACK; Use FindTopOfStack() */

 void GC_push_all_stacks() {
     int i;
     kern_return_t r;
     mach_port_t me;
     ptr_t lo, hi;
     thread_act_array_t act_list = 0;
     mach_msg_type_number_t listcount = 0;

     me = mach_thread_self();
     if (!GC_thr_initialized) GC_thr_init();

     r = task_threads(current_task(), &act_list, &listcount);
     if(r != KERN_SUCCESS) ABORT("task_threads failed");
     for(i = 0; i < listcount; i++) {
       thread_act_t thread = act_list[i];
       if (thread == me) {
 	lo = GC_approx_sp();
 	hi = (ptr_t)FindTopOfStack(0);
       } else {
 #     if defined(__ppc__) || defined(__ppc64__)
 	GC_THREAD_STATE_T info;
 	mach_msg_type_number_t outCount = THREAD_STATE_MAX;
 	r = thread_get_state(thread, GC_MACH_THREAD_STATE,
 			     (natural_t *)&info, &outCount);
 	if(r != KERN_SUCCESS) ABORT("task_get_state failed");

 	lo = (void*)(info . THREAD_FLD (r1) - PPC_RED_ZONE_SIZE);
 	hi = (ptr_t)FindTopOfStack(info . THREAD_FLD (r1));

 	GC_push_one(info . THREAD_FLD (r0));
 	GC_push_one(info . THREAD_FLD (r2));
 	GC_push_one(info . THREAD_FLD (r3));
 	GC_push_one(info . THREAD_FLD (r4));
 	GC_push_one(info . THREAD_FLD (r5));
 	GC_push_one(info . THREAD_FLD (r6));
 	GC_push_one(info . THREAD_FLD (r7));
 	GC_push_one(info . THREAD_FLD (r8));
 	GC_push_one(info . THREAD_FLD (r9));
 	GC_push_one(info . THREAD_FLD (r10));
 	GC_push_one(info . THREAD_FLD (r11));
 	GC_push_one(info . THREAD_FLD (r12));
 	GC_push_one(info . THREAD_FLD (r13));
 	GC_push_one(info . THREAD_FLD (r14));
 	GC_push_one(info . THREAD_FLD (r15));
 	GC_push_one(info . THREAD_FLD (r16));
 	GC_push_one(info . THREAD_FLD (r17));
 	GC_push_one(info . THREAD_FLD (r18));
 	GC_push_one(info . THREAD_FLD (r19));
 	GC_push_one(info . THREAD_FLD (r20));
 	GC_push_one(info . THREAD_FLD (r21));
 	GC_push_one(info . THREAD_FLD (r22));
 	GC_push_one(info . THREAD_FLD (r23));
 	GC_push_one(info . THREAD_FLD (r24));
 	GC_push_one(info . THREAD_FLD (r25));
 	GC_push_one(info . THREAD_FLD (r26));
 	GC_push_one(info . THREAD_FLD (r27));
 	GC_push_one(info . THREAD_FLD (r28));
 	GC_push_one(info . THREAD_FLD (r29));
 	GC_push_one(info . THREAD_FLD (r30));
 	GC_push_one(info . THREAD_FLD (r31));
 #      else
 	/* FIXME: Remove after testing:	*/
 	WARN("This is completely untested and likely will not work\n", 0);
 	GC_THREAD_STATE_T info;
 	mach_msg_type_number_t outCount = THREAD_STATE_MAX;
 	r = thread_get_state(thread, GC_MACH_THREAD_STATE, (natural_t *)&info,
 			     &outCount);
 	if(r != KERN_SUCCESS) ABORT("task_get_state failed");

 	lo = (void*)info . THREAD_FLD (esp);
 	hi = (ptr_t)FindTopOfStack(info . THREAD_FLD (esp));

 	GC_push_one(info . THREAD_FLD (eax));
 	GC_push_one(info . THREAD_FLD (ebx));
 	GC_push_one(info . THREAD_FLD (ecx));
 	GC_push_one(info . THREAD_FLD (edx));
 	GC_push_one(info . THREAD_FLD (edi));
 	GC_push_one(info . THREAD_FLD (esi));
 	/* GC_push_one(info . THREAD_FLD (ebp));  */
 	/* GC_push_one(info . THREAD_FLD (esp));  */
 	GC_push_one(info . THREAD_FLD (ss));
 	GC_push_one(info . THREAD_FLD (eip));
 	GC_push_one(info . THREAD_FLD (cs));
 	GC_push_one(info . THREAD_FLD (ds));
 	GC_push_one(info . THREAD_FLD (es));
 	GC_push_one(info . THREAD_FLD (fs));
 	GC_push_one(info . THREAD_FLD (gs));
 #      endif /* !POWERPC */
       }
 #     if DEBUG_THREADS
        GC_printf3("Darwin: Stack for thread 0x%lx = [%lx,%lx)\n",
 		  (unsigned long) thread,
 		  (unsigned long) lo,
 		  (unsigned long) hi
 		 );
 #     endif
       GC_push_all_stack(lo, hi);
     } /* for(p=GC_threads[i]...) */
     vm_deallocate(current_task(), (vm_address_t)act_list, sizeof(thread_t) * listcount);
 }
 #endif /* !DARWIN_DONT_PARSE_STACK */

 static mach_port_t GC_mach_handler_thread;
 static int GC_use_mach_handler_thread = 0;

 static struct GC_mach_thread GC_mach_threads[THREAD_TABLE_SZ];
 static int GC_mach_threads_count;

 void GC_stop_init() {
   int i;

   for (i = 0; i < THREAD_TABLE_SZ; i++) {
     GC_mach_threads[i].thread = 0;
     GC_mach_threads[i].already_suspended = 0;
   }
   GC_mach_threads_count = 0;
 }

 /* returns true if there's a thread in act_list that wasn't in old_list */
 int GC_suspend_thread_list(thread_act_array_t act_list, int count,
 			   thread_act_array_t old_list, int old_count) {
   mach_port_t my_thread = mach_thread_self();
   int i, j;

   int changed = 0;

   for(i = 0; i < count; i++) {
     thread_act_t thread = act_list[i];
 #   if DEBUG_THREADS
       GC_printf1("Attempting to suspend thread %p\n", thread);
 #   endif
     /* find the current thread in the old list */
     int found = 0;
     for(j = 0; j < old_count; j++) {
       thread_act_t old_thread = old_list[j];
       if (old_thread == thread) {
 	found = 1;
 	break;
       }
     }
     if (!found) {
       /* add it to the GC_mach_threads list */
       GC_mach_threads[GC_mach_threads_count].thread = thread;
       /* default is not suspended */
       GC_mach_threads[GC_mach_threads_count].already_suspended = 0;
       changed = 1;
     }

     if (thread != my_thread &&
 	(!GC_use_mach_handler_thread
 	 || (GC_use_mach_handler_thread
 	     && GC_mach_handler_thread != thread))) {
       struct thread_basic_info info;
       mach_msg_type_number_t outCount = THREAD_INFO_MAX;
       kern_return_t kern_result = thread_info(thread, THREAD_BASIC_INFO,
 				(thread_info_t)&info, &outCount);
       if(kern_result != KERN_SUCCESS) {
 	/* the thread may have quit since the thread_threads () call
 	 * we mark already_suspended so it's not dealt with anymore later
 	 */
         if (!found) {
 	  GC_mach_threads[GC_mach_threads_count].already_suspended = TRUE;
     	  GC_mach_threads_count++;
 	}
 	continue;
       }
 #     if DEBUG_THREADS
         GC_printf2("Thread state for 0x%lx = %d\n", thread, info.run_state);
 #     endif
       if (!found) {
 	GC_mach_threads[GC_mach_threads_count].already_suspended = info.suspend_count;
       }
       if (info.suspend_count) continue;

 #     if DEBUG_THREADS
         GC_printf1("Suspending 0x%lx\n", thread);
 #     endif
       /* Suspend the thread */
       kern_result = thread_suspend(thread);
       if(kern_result != KERN_SUCCESS) {
 	/* the thread may have quit since the thread_threads () call
 	 * we mark already_suspended so it's not dealt with anymore later
 	 */
         if (!found) {
 	  GC_mach_threads[GC_mach_threads_count].already_suspended = TRUE;
     	  GC_mach_threads_count++;
 	}
 	continue;
       }
     }
     if (!found) GC_mach_threads_count++;
   }
   return changed;
 }


 /* Caller holds allocation lock.	*/
 void GC_stop_world()
 {
   int i, changes;
     GC_thread p;
     mach_port_t my_thread = mach_thread_self();
     kern_return_t kern_result;
     thread_act_array_t act_list, prev_list;
     mach_msg_type_number_t listcount, prevcount;

 #   if DEBUG_THREADS
       GC_printf1("Stopping the world from 0x%lx\n", mach_thread_self());
 #   endif

     /* clear out the mach threads list table */
     GC_stop_init();

     /* Make sure all free list construction has stopped before we start. */
     /* No new construction can start, since free list construction is	*/
     /* required to acquire and release the GC lock before it starts,	*/
     /* and we have the lock.						*/
 #   ifdef PARALLEL_MARK
       GC_acquire_mark_lock();
       GC_ASSERT(GC_fl_builder_count == 0);
       /* We should have previously waited for it to become zero. */
 #   endif /* PARALLEL_MARK */

       /* Loop stopping threads until you have gone over the whole list
 	 twice without a new one appearing. thread_create() won't
 	 return (and thus the thread stop) until the new thread
 	 exists, so there is no window whereby you could stop a
 	 thread, recognise it is stopped, but then have a new thread
 	 it created before stopping show up later.
       */

       changes = 1;
       prev_list = NULL;
       prevcount = 0;
       do {
 	int result;
 	kern_result = task_threads(current_task(), &act_list, &listcount);
 	result = GC_suspend_thread_list(act_list, listcount,
 					prev_list, prevcount);
 	changes = result;
 	prev_list = act_list;
 	prevcount = listcount;
         vm_deallocate(current_task(), (vm_address_t)act_list, sizeof(thread_t) * listcount);
       } while (changes);


 #   ifdef MPROTECT_VDB
       if(GC_incremental) {
         extern void GC_mprotect_stop();
         GC_mprotect_stop();
       }
 #   endif

 #   ifdef PARALLEL_MARK
       GC_release_mark_lock();
 #   endif
     #if DEBUG_THREADS
       GC_printf1("World stopped from 0x%lx\n", my_thread);
     #endif
 }

 /* Caller holds allocation lock, and has held it continuously since	*/
 /* the world stopped.							*/
 void GC_start_world()
 {
   mach_port_t my_thread = mach_thread_self();
   int i, j;
   GC_thread p;
   kern_return_t kern_result;
   thread_act_array_t act_list;
   mach_msg_type_number_t listcount;
   struct thread_basic_info info;
   mach_msg_type_number_t outCount = THREAD_INFO_MAX;

 #   if DEBUG_THREADS
       GC_printf0("World starting\n");
 #   endif

 #   ifdef MPROTECT_VDB
       if(GC_incremental) {
         extern void GC_mprotect_resume();
         GC_mprotect_resume();
       }
 #   endif

     kern_result = task_threads(current_task(), &act_list, &listcount);
     for(i = 0; i < listcount; i++) {
       thread_act_t thread = act_list[i];
       if (thread != my_thread &&
 	  (!GC_use_mach_handler_thread ||
 	   (GC_use_mach_handler_thread && GC_mach_handler_thread != thread))) {
 	for(j = 0; j < GC_mach_threads_count; j++) {
 	  if (thread == GC_mach_threads[j].thread) {
 	    if (GC_mach_threads[j].already_suspended) {
 #             if DEBUG_THREADS
 	        GC_printf1("Not resuming already suspended thread %p\n", thread);
 #             endif
 	      continue;
 	    }
 	    kern_result = thread_info(thread, THREAD_BASIC_INFO,
 				      (thread_info_t)&info, &outCount);
 	    if(kern_result != KERN_SUCCESS) ABORT("thread_info failed");
 #           if DEBUG_THREADS
 	      GC_printf2("Thread state for 0x%lx = %d\n", thread,
 			 info.run_state);
 	      GC_printf1("Resuming 0x%lx\n", thread);
 #           endif
 	    /* Resume the thread */
 	    kern_result = thread_resume(thread);
 	    if(kern_result != KERN_SUCCESS) ABORT("thread_resume failed");
 	  }
 	}
       }
     }
     vm_deallocate(current_task(), (vm_address_t)act_list, sizeof(thread_t) * listcount);
 #   if DEBUG_THREADS
      GC_printf0("World started\n");
 #   endif
 }

 void GC_darwin_register_mach_handler_thread(mach_port_t thread) {
   GC_mach_handler_thread = thread;
   GC_use_mach_handler_thread = 1;
 }

 #endif
	#include "private/pthread_support.h"

	/* This probably needs more porting work to ppc64. */

	# if defined(GC_DARWIN_THREADS)

	/* From "Inside Mac OS X - Mach-O Runtime Architecture" published by Apple
	Page 49:
	"The space beneath the stack pointer, where a new stack frame would normally
	be allocated, is called the red zone. This area as shown in Figure 3-2 may
	be used for any purpose as long as a new stack frame does not need to be
	added to the stack."

	Page 50: "If a leaf procedure's red zone usage would exceed 224 bytes, then
	it must set up a stack frame just like routines that call other routines."
	*/
	#if defined(__ppc__)
	# define PPC_RED_ZONE_SIZE 224
	#elif defined(__ppc64__)
	# define PPC_RED_ZONE_SIZE 320
	#endif

	typedef struct StackFrame {
	unsigned long savedSP;
	unsigned long savedCR;
	unsigned long savedLR;
	unsigned long reserved[2];
	unsigned long savedRTOC;
	} StackFrame;

	unsigned long FindTopOfStack(unsigned long stack_start) {
	StackFrame *frame;

	if (stack_start == 0) {
	# ifdef POWERPC
	# if CPP_WORDSZ == 32
	__asm__ volatile("lwz %0,0(r1)" : "=r" (frame));
	# else
	__asm__ volatile("ld %0,0(r1)" : "=r" (frame));
	# endif
	# endif
	} else {
	frame = (StackFrame *)stack_start;
	}

	# ifdef DEBUG_THREADS
	/* GC_printf1("FindTopOfStack start at sp = %p\n", frame); */
	# endif
	do {
	if (frame->savedSP == 0) break;
	/* if there are no more stack frames, stop */

	frame = (StackFrame*)frame->savedSP;

	/* we do these next two checks after going to the next frame
	because the LR for the first stack frame in the loop
	is not set up on purpose, so we shouldn't check it. */
	if ((frame->savedLR & ~3) == 0) break; /* if the next LR is bogus, stop */
	if ((~(frame->savedLR) & ~3) == 0) break; /* ditto */
	} while (1);

	# ifdef DEBUG_THREADS
	/* GC_printf1("FindTopOfStack finish at sp = %p\n", frame); */
	# endif

	return (unsigned long)frame;
	}

	#ifdef DARWIN_DONT_PARSE_STACK
	void GC_push_all_stacks() {
	int i;
	kern_return_t r;
	GC_thread p;
	pthread_t me;
	ptr_t lo, hi;
	GC_THREAD_STATE_T state;
	mach_msg_type_number_t thread_state_count = GC_MACH_THREAD_STATE_COUNT;

	me = pthread_self();
	if (!GC_thr_initialized) GC_thr_init();

	for(i=0;i<THREAD_TABLE_SZ;i++) {
	for(p=GC_threads[i];p!=0;p=p->next) {
	if(p -> flags & FINISHED) continue;
	if(pthread_equal(p->id,me)) {
	lo = GC_approx_sp();
	} else {
	/* Get the thread state (registers, etc) */
	r = thread_get_state(p->stop_info.mach_thread, GC_MACH_THREAD_STATE,
	(natural_t*)&state, &thread_state_count);
	if(r != KERN_SUCCESS) ABORT("thread_get_state failed");

	#if defined(I386)
	lo = (void*)state . THREAD_FLD (esp);

	GC_push_one(state . THREAD_FLD (eax));
	GC_push_one(state . THREAD_FLD (ebx));
	GC_push_one(state . THREAD_FLD (ecx));
	GC_push_one(state . THREAD_FLD (edx));
	GC_push_one(state . THREAD_FLD (edi));
	GC_push_one(state . THREAD_FLD (esi));
	GC_push_one(state . THREAD_FLD (ebp));

	#elif defined(X86_64)
	lo = (void*)state . THREAD_FLD (rsp);

	GC_push_one(state . THREAD_FLD (rax));
	GC_push_one(state . THREAD_FLD (rbx));
	GC_push_one(state . THREAD_FLD (rcx));
	GC_push_one(state . THREAD_FLD (rdx));
	GC_push_one(state . THREAD_FLD (rdi));
	GC_push_one(state . THREAD_FLD (rsi));
	GC_push_one(state . THREAD_FLD (rbp));
	GC_push_one(state . THREAD_FLD (rsp));
	GC_push_one(state . THREAD_FLD (r8));
	GC_push_one(state . THREAD_FLD (r9));
	GC_push_one(state . THREAD_FLD (r10));
	GC_push_one(state . THREAD_FLD (r11));
	GC_push_one(state . THREAD_FLD (r12));
	GC_push_one(state . THREAD_FLD (r13));
	GC_push_one(state . THREAD_FLD (r14));
	GC_push_one(state . THREAD_FLD (r15));
	GC_push_one(state . THREAD_FLD (rip));
	GC_push_one(state . THREAD_FLD (rflags));
	GC_push_one(state . THREAD_FLD (cs));
	GC_push_one(state . THREAD_FLD (fs));
	GC_push_one(state . THREAD_FLD (gs));

	#elif defined(POWERPC)
	lo = (void*)(state . THREAD_FLD (r1) - PPC_RED_ZONE_SIZE);

	GC_push_one(state . THREAD_FLD (r0));
	GC_push_one(state . THREAD_FLD (r2));
	GC_push_one(state . THREAD_FLD (r3));
	GC_push_one(state . THREAD_FLD (r4));
	GC_push_one(state . THREAD_FLD (r5));
	GC_push_one(state . THREAD_FLD (r6));
	GC_push_one(state . THREAD_FLD (r7));
	GC_push_one(state . THREAD_FLD (r8));
	GC_push_one(state . THREAD_FLD (r9));
	GC_push_one(state . THREAD_FLD (r10));
	GC_push_one(state . THREAD_FLD (r11));
	GC_push_one(state . THREAD_FLD (r12));
	GC_push_one(state . THREAD_FLD (r13));
	GC_push_one(state . THREAD_FLD (r14));
	GC_push_one(state . THREAD_FLD (r15));
	GC_push_one(state . THREAD_FLD (r16));
	GC_push_one(state . THREAD_FLD (r17));
	GC_push_one(state . THREAD_FLD (r18));
	GC_push_one(state . THREAD_FLD (r19));
	GC_push_one(state . THREAD_FLD (r20));
	GC_push_one(state . THREAD_FLD (r21));
	GC_push_one(state . THREAD_FLD (r22));
	GC_push_one(state . THREAD_FLD (r23));
	GC_push_one(state . THREAD_FLD (r24));
	GC_push_one(state . THREAD_FLD (r25));
	GC_push_one(state . THREAD_FLD (r26));
	GC_push_one(state . THREAD_FLD (r27));
	GC_push_one(state . THREAD_FLD (r28));
	GC_push_one(state . THREAD_FLD (r29));
	GC_push_one(state . THREAD_FLD (r30));
	GC_push_one(state . THREAD_FLD (r31));
	#else
	# error FIXME for non-x86 \|\| ppc architectures
	#endif
	} /* p != me */
	if(p->flags & MAIN_THREAD)
	hi = GC_stackbottom;
	else
	hi = p->stack_end;
	#if DEBUG_THREADS
	GC_printf3("Darwin: Stack for thread 0x%lx = [%lx,%lx)\n",
	(unsigned long) p -> id,
	(unsigned long) lo,
	(unsigned long) hi
	);
	#endif
	GC_push_all_stack(lo,hi);
	} /* for(p=GC_threads[i]...) */
	} /* for(i=0;i<THREAD_TABLE_SZ...) */
	}

	#else /* !DARWIN_DONT_PARSE_STACK; Use FindTopOfStack() */

	void GC_push_all_stacks() {
	int i;
	kern_return_t r;
	mach_port_t me;
	ptr_t lo, hi;
	thread_act_array_t act_list = 0;
	mach_msg_type_number_t listcount = 0;

	me = mach_thread_self();
	if (!GC_thr_initialized) GC_thr_init();

	r = task_threads(current_task(), &act_list, &listcount);
	if(r != KERN_SUCCESS) ABORT("task_threads failed");
	for(i = 0; i < listcount; i++) {
	thread_act_t thread = act_list[i];
	if (thread == me) {
	lo = GC_approx_sp();
	hi = (ptr_t)FindTopOfStack(0);
	} else {
	# if defined(__ppc__) \|\| defined(__ppc64__)
	GC_THREAD_STATE_T info;
	mach_msg_type_number_t outCount = THREAD_STATE_MAX;
	r = thread_get_state(thread, GC_MACH_THREAD_STATE,
	(natural_t *)&info, &outCount);
	if(r != KERN_SUCCESS) ABORT("task_get_state failed");

	lo = (void*)(info . THREAD_FLD (r1) - PPC_RED_ZONE_SIZE);
	hi = (ptr_t)FindTopOfStack(info . THREAD_FLD (r1));

	GC_push_one(info . THREAD_FLD (r0));
	GC_push_one(info . THREAD_FLD (r2));
	GC_push_one(info . THREAD_FLD (r3));
	GC_push_one(info . THREAD_FLD (r4));
	GC_push_one(info . THREAD_FLD (r5));
	GC_push_one(info . THREAD_FLD (r6));
	GC_push_one(info . THREAD_FLD (r7));
	GC_push_one(info . THREAD_FLD (r8));
	GC_push_one(info . THREAD_FLD (r9));
	GC_push_one(info . THREAD_FLD (r10));
	GC_push_one(info . THREAD_FLD (r11));
	GC_push_one(info . THREAD_FLD (r12));
	GC_push_one(info . THREAD_FLD (r13));
	GC_push_one(info . THREAD_FLD (r14));
	GC_push_one(info . THREAD_FLD (r15));
	GC_push_one(info . THREAD_FLD (r16));
	GC_push_one(info . THREAD_FLD (r17));
	GC_push_one(info . THREAD_FLD (r18));
	GC_push_one(info . THREAD_FLD (r19));
	GC_push_one(info . THREAD_FLD (r20));
	GC_push_one(info . THREAD_FLD (r21));
	GC_push_one(info . THREAD_FLD (r22));
	GC_push_one(info . THREAD_FLD (r23));
	GC_push_one(info . THREAD_FLD (r24));
	GC_push_one(info . THREAD_FLD (r25));
	GC_push_one(info . THREAD_FLD (r26));
	GC_push_one(info . THREAD_FLD (r27));
	GC_push_one(info . THREAD_FLD (r28));
	GC_push_one(info . THREAD_FLD (r29));
	GC_push_one(info . THREAD_FLD (r30));
	GC_push_one(info . THREAD_FLD (r31));
	# else
	/* FIXME: Remove after testing: */
	WARN("This is completely untested and likely will not work\n", 0);
	GC_THREAD_STATE_T info;
	mach_msg_type_number_t outCount = THREAD_STATE_MAX;
	r = thread_get_state(thread, GC_MACH_THREAD_STATE, (natural_t *)&info,
	&outCount);
	if(r != KERN_SUCCESS) ABORT("task_get_state failed");

	lo = (void*)info . THREAD_FLD (esp);
	hi = (ptr_t)FindTopOfStack(info . THREAD_FLD (esp));

	GC_push_one(info . THREAD_FLD (eax));
	GC_push_one(info . THREAD_FLD (ebx));
	GC_push_one(info . THREAD_FLD (ecx));
	GC_push_one(info . THREAD_FLD (edx));
	GC_push_one(info . THREAD_FLD (edi));
	GC_push_one(info . THREAD_FLD (esi));
	/* GC_push_one(info . THREAD_FLD (ebp)); */
	/* GC_push_one(info . THREAD_FLD (esp)); */
	GC_push_one(info . THREAD_FLD (ss));
	GC_push_one(info . THREAD_FLD (eip));
	GC_push_one(info . THREAD_FLD (cs));
	GC_push_one(info . THREAD_FLD (ds));
	GC_push_one(info . THREAD_FLD (es));
	GC_push_one(info . THREAD_FLD (fs));
	GC_push_one(info . THREAD_FLD (gs));
	# endif /* !POWERPC */
	}
	# if DEBUG_THREADS
	GC_printf3("Darwin: Stack for thread 0x%lx = [%lx,%lx)\n",
	(unsigned long) thread,
	(unsigned long) lo,
	(unsigned long) hi
	);
	# endif
	GC_push_all_stack(lo, hi);
	} /* for(p=GC_threads[i]...) */
	vm_deallocate(current_task(), (vm_address_t)act_list, sizeof(thread_t) * listcount);
	}
	#endif /* !DARWIN_DONT_PARSE_STACK */

	static mach_port_t GC_mach_handler_thread;
	static int GC_use_mach_handler_thread = 0;

	static struct GC_mach_thread GC_mach_threads[THREAD_TABLE_SZ];
	static int GC_mach_threads_count;

	void GC_stop_init() {
	int i;

	for (i = 0; i < THREAD_TABLE_SZ; i++) {
	GC_mach_threads[i].thread = 0;
	GC_mach_threads[i].already_suspended = 0;
	}
	GC_mach_threads_count = 0;
	}

	/* returns true if there's a thread in act_list that wasn't in old_list */
	int GC_suspend_thread_list(thread_act_array_t act_list, int count,
	thread_act_array_t old_list, int old_count) {
	mach_port_t my_thread = mach_thread_self();
	int i, j;

	int changed = 0;

	for(i = 0; i < count; i++) {
	thread_act_t thread = act_list[i];
	# if DEBUG_THREADS
	GC_printf1("Attempting to suspend thread %p\n", thread);
	# endif
	/* find the current thread in the old list */
	int found = 0;
	for(j = 0; j < old_count; j++) {
	thread_act_t old_thread = old_list[j];
	if (old_thread == thread) {
	found = 1;
	break;
	}
	}
	if (!found) {
	/* add it to the GC_mach_threads list */
	GC_mach_threads[GC_mach_threads_count].thread = thread;
	/* default is not suspended */
	GC_mach_threads[GC_mach_threads_count].already_suspended = 0;
	changed = 1;
	}

	if (thread != my_thread &&
	(!GC_use_mach_handler_thread
	\|\| (GC_use_mach_handler_thread
	&& GC_mach_handler_thread != thread))) {
	struct thread_basic_info info;
	mach_msg_type_number_t outCount = THREAD_INFO_MAX;
	kern_return_t kern_result = thread_info(thread, THREAD_BASIC_INFO,
	(thread_info_t)&info, &outCount);
	if(kern_result != KERN_SUCCESS) {
	/* the thread may have quit since the thread_threads () call
	* we mark already_suspended so it's not dealt with anymore later
	*/
	if (!found) {
	GC_mach_threads[GC_mach_threads_count].already_suspended = TRUE;
	GC_mach_threads_count++;
	}
	continue;
	}
	# if DEBUG_THREADS
	GC_printf2("Thread state for 0x%lx = %d\n", thread, info.run_state);
	# endif
	if (!found) {
	GC_mach_threads[GC_mach_threads_count].already_suspended = info.suspend_count;
	}
	if (info.suspend_count) continue;

	# if DEBUG_THREADS
	GC_printf1("Suspending 0x%lx\n", thread);
	# endif
	/* Suspend the thread */
	kern_result = thread_suspend(thread);
	if(kern_result != KERN_SUCCESS) {
	/* the thread may have quit since the thread_threads () call
	* we mark already_suspended so it's not dealt with anymore later
	*/
	if (!found) {
	GC_mach_threads[GC_mach_threads_count].already_suspended = TRUE;
	GC_mach_threads_count++;
	}
	continue;
	}
	}
	if (!found) GC_mach_threads_count++;
	}
	return changed;
	}


	/* Caller holds allocation lock. */
	void GC_stop_world()
	{
	int i, changes;
	GC_thread p;
	mach_port_t my_thread = mach_thread_self();
	kern_return_t kern_result;
	thread_act_array_t act_list, prev_list;
	mach_msg_type_number_t listcount, prevcount;

	# if DEBUG_THREADS
	GC_printf1("Stopping the world from 0x%lx\n", mach_thread_self());
	# endif

	/* clear out the mach threads list table */
	GC_stop_init();

	/* Make sure all free list construction has stopped before we start. */
	/* No new construction can start, since free list construction is */
	/* required to acquire and release the GC lock before it starts, */
	/* and we have the lock. */
	# ifdef PARALLEL_MARK
	GC_acquire_mark_lock();
	GC_ASSERT(GC_fl_builder_count == 0);
	/* We should have previously waited for it to become zero. */
	# endif /* PARALLEL_MARK */

	/* Loop stopping threads until you have gone over the whole list
	twice without a new one appearing. thread_create() won't
	return (and thus the thread stop) until the new thread
	exists, so there is no window whereby you could stop a
	thread, recognise it is stopped, but then have a new thread
	it created before stopping show up later.
	*/

	changes = 1;
	prev_list = NULL;
	prevcount = 0;
	do {
	int result;
	kern_result = task_threads(current_task(), &act_list, &listcount);
	result = GC_suspend_thread_list(act_list, listcount,
	prev_list, prevcount);
	changes = result;
	prev_list = act_list;
	prevcount = listcount;
	vm_deallocate(current_task(), (vm_address_t)act_list, sizeof(thread_t) * listcount);
	} while (changes);


	# ifdef MPROTECT_VDB
	if(GC_incremental) {
	extern void GC_mprotect_stop();
	GC_mprotect_stop();
	}
	# endif

	# ifdef PARALLEL_MARK
	GC_release_mark_lock();
	# endif
	#if DEBUG_THREADS
	GC_printf1("World stopped from 0x%lx\n", my_thread);
	#endif
	}

	/* Caller holds allocation lock, and has held it continuously since */
	/* the world stopped. */
	void GC_start_world()
	{
	mach_port_t my_thread = mach_thread_self();
	int i, j;
	GC_thread p;
	kern_return_t kern_result;
	thread_act_array_t act_list;
	mach_msg_type_number_t listcount;
	struct thread_basic_info info;
	mach_msg_type_number_t outCount = THREAD_INFO_MAX;

	# if DEBUG_THREADS
	GC_printf0("World starting\n");
	# endif

	# ifdef MPROTECT_VDB
	if(GC_incremental) {
	extern void GC_mprotect_resume();
	GC_mprotect_resume();
	}
	# endif

	kern_result = task_threads(current_task(), &act_list, &listcount);
	for(i = 0; i < listcount; i++) {
	thread_act_t thread = act_list[i];
	if (thread != my_thread &&
	(!GC_use_mach_handler_thread \|\|
	(GC_use_mach_handler_thread && GC_mach_handler_thread != thread))) {
	for(j = 0; j < GC_mach_threads_count; j++) {
	if (thread == GC_mach_threads[j].thread) {
	if (GC_mach_threads[j].already_suspended) {
	# if DEBUG_THREADS
	GC_printf1("Not resuming already suspended thread %p\n", thread);
	# endif
	continue;
	}
	kern_result = thread_info(thread, THREAD_BASIC_INFO,
	(thread_info_t)&info, &outCount);
	if(kern_result != KERN_SUCCESS) ABORT("thread_info failed");
	# if DEBUG_THREADS
	GC_printf2("Thread state for 0x%lx = %d\n", thread,
	info.run_state);
	GC_printf1("Resuming 0x%lx\n", thread);
	# endif
	/* Resume the thread */
	kern_result = thread_resume(thread);
	if(kern_result != KERN_SUCCESS) ABORT("thread_resume failed");
	}
	}
	}
	}
	vm_deallocate(current_task(), (vm_address_t)act_list, sizeof(thread_t) * listcount);
	# if DEBUG_THREADS
	GC_printf0("World started\n");
	# endif
	}

	void GC_darwin_register_mach_handler_thread(mach_port_t thread) {
	GC_mach_handler_thread = thread;
	GC_use_mach_handler_thread = 1;
	}

	#endif