gc.c

/*
 * metadata/gc.c: GC icalls.
 *
 * Author: Paolo Molaro <lupus@ximian.com>
 *
 * (C) 2002 Ximian, Inc.
 */

#include <config.h>
#include <glib.h>
#include <string.h>

#include <mono/metadata/gc-internal.h>
#include <mono/metadata/mono-gc.h>
#include <mono/metadata/threads.h>
#include <mono/metadata/tabledefs.h>
#include <mono/metadata/exception.h>
#include <mono/metadata/profiler-private.h>
#include <mono/metadata/domain-internals.h>
#include <mono/metadata/class-internals.h>
#include <mono/utils/mono-logger.h>
#include <mono/os/gc_wrapper.h>
#include <mono/metadata/marshal.h> /* for mono_delegate_free_ftnptr () */

typedef struct DomainFinalizationReq {
	MonoDomain *domain;
	HANDLE done_event;
} DomainFinalizationReq;

#ifdef PLATFORM_WINCE /* FIXME: add accessors to gc.dll API */
extern void (*__imp_GC_finalizer_notifier)(void);
#define GC_finalizer_notifier __imp_GC_finalizer_notifier
extern int __imp_GC_finalize_on_demand;
#define GC_finalize_on_demand __imp_GC_finalize_on_demand
#endif

static gboolean gc_disabled = FALSE;

#define mono_finalizer_lock() EnterCriticalSection (&finalizer_mutex)
#define mono_finalizer_unlock() LeaveCriticalSection (&finalizer_mutex)
static CRITICAL_SECTION finalizer_mutex;

static GSList *domains_to_finalize= NULL;

static MonoThread *gc_thread;

static void object_register_finalizer (MonoObject *obj, void (*callback)(void *, void*));

#ifndef HAVE_NULL_GC
static HANDLE pending_done_event;
static HANDLE shutdown_event;
static HANDLE thread_started_event;
#endif

/* 
 * actually, we might want to queue the finalize requests in a separate thread,
 * but we need to be careful about the execution domain of the thread...
 */
static void
run_finalize (void *obj, void *data)
{
	MonoObject *exc = NULL;
	MonoObject *o, *o2;
	o = (MonoObject*)((char*)obj + GPOINTER_TO_UINT (data));

#ifndef HAVE_SGEN_GC
	mono_domain_lock (o->vtable->domain);

	o2 = g_hash_table_lookup (o->vtable->domain->finalizable_objects_hash, o);

	mono_domain_unlock (o->vtable->domain);

	if (!o2)
		/* Already finalized somehow */
		return;
#endif

	/* make sure the finalizer is not called again if the object is resurrected */
	object_register_finalizer (obj, NULL);

	if (o->vtable->klass == mono_get_thread_class ())
		if (mono_gc_is_finalizer_thread ((MonoThread*)o))
			/* Avoid finalizing ourselves */
			return;

	/* speedup later... and use a timeout */
	/* g_print ("Finalize run on %p %s.%s\n", o, mono_object_class (o)->name_space, mono_object_class (o)->name); */

	/* Use _internal here, since this thread can enter a doomed appdomain */
	mono_domain_set_internal (mono_object_domain (o));		

	/* delegates that have a native function pointer allocated are
	 * registered for finalization, but they don't have a Finalize
	 * method, because in most cases it's not needed and it's just a waste.
	 */
	if (o->vtable->klass->delegate) {
		MonoDelegate* del = (MonoDelegate*)o;
		if (del->delegate_trampoline)
			mono_delegate_free_ftnptr ((MonoDelegate*)o);
		return;
	}

	mono_runtime_invoke (mono_class_get_finalizer (o->vtable->klass), o, NULL, &exc);

	if (exc) {
		/* fixme: do something useful */
	}
}

gpointer
mono_gc_out_of_memory (size_t size)
{
	/* 
	 * we could allocate at program startup some memory that we could release 
	 * back to the system at this point if we're really low on memory (ie, size is
	 * lower than the memory we set apart)
	 */
	mono_raise_exception (mono_domain_get ()->out_of_memory_ex);

	return NULL;
}

/*
 * Some of our objects may point to a different address than the address returned by GC_malloc()
 * (because of the GetHashCode hack), but we need to pass the real address to register_finalizer.
 * This also means that in the callback we need to adjust the pointer to get back the real
 * MonoObject*.
 * We also need to be consistent in the use of the GC_debug* variants of malloc and register_finalizer, 
 * since that, too, can cause the underlying pointer to be offset.
 */
static void
object_register_finalizer (MonoObject *obj, void (*callback)(void *, void*))
{
#if HAVE_BOEHM_GC
	guint offset = 0;

#ifndef GC_DEBUG
	/* This assertion is not valid when GC_DEBUG is defined */
	g_assert (GC_base (obj) == (char*)obj - offset);
#endif

	if (mono_domain_is_unloading (obj->vtable->domain) && (callback != NULL))
		/*
		 * Can't register finalizers in a dying appdomain, since they
		 * could be invoked after the appdomain has been unloaded.
		 */
		return;

	mono_domain_lock (obj->vtable->domain);

	if (callback)
		g_hash_table_insert (obj->vtable->domain->finalizable_objects_hash, obj,
							 obj);
	else
		g_hash_table_remove (obj->vtable->domain->finalizable_objects_hash, obj);

	mono_domain_unlock (obj->vtable->domain);

	GC_REGISTER_FINALIZER_NO_ORDER ((char*)obj - offset, callback, GUINT_TO_POINTER (offset), NULL, NULL);
#elif defined(HAVE_SGEN_GC)
	mono_gc_register_for_finalization (obj, callback);
#endif
}

/**
 * mono_object_register_finalizer:
 * @obj: object to register
 *
 * Records that object @obj has a finalizer, this will call the
 * Finalize method when the garbage collector disposes the object.
 * 
 */
void
mono_object_register_finalizer (MonoObject *obj)
{
	/* g_print ("Registered finalizer on %p %s.%s\n", obj, mono_object_class (obj)->name_space, mono_object_class (obj)->name); */
	object_register_finalizer (obj, run_finalize);
}

/**
 * mono_domain_finalize:
 * @domain: the domain to finalize
 * @timeout: msects to wait for the finalization to complete
 *
 *  Request finalization of all finalizable objects inside @domain. Wait
 * @timeout msecs for the finalization to complete.
 *
 * Returns: TRUE if succeeded, FALSE if there was a timeout
 */

gboolean
mono_domain_finalize (MonoDomain *domain, guint32 timeout) 
{
	DomainFinalizationReq *req;
	guint32 res;
	HANDLE done_event;

	if (mono_thread_current () == gc_thread)
		/* We are called from inside a finalizer, not much we can do here */
		return FALSE;

	mono_profiler_appdomain_event (domain, MONO_PROFILE_START_UNLOAD);

	/* 
	 * No need to create another thread 'cause the finalizer thread
	 * is still working and will take care of running the finalizers
	 */ 
	
#ifndef HAVE_NULL_GC
	if (gc_disabled)
		return TRUE;

	mono_gc_collect (mono_gc_max_generation ());

	done_event = CreateEvent (NULL, TRUE, FALSE, NULL);

	req = g_new0 (DomainFinalizationReq, 1);
	req->domain = domain;
	req->done_event = done_event;
	
	mono_finalizer_lock ();

	domains_to_finalize = g_slist_append (domains_to_finalize, req);

	mono_finalizer_unlock ();

	/* Tell the finalizer thread to finalize this appdomain */
	mono_gc_finalize_notify ();

	res = WaitForSingleObjectEx (done_event, timeout, TRUE);

	/* printf ("WAIT RES: %d.\n", res); */
	if (res == WAIT_TIMEOUT) {
		/* We leak the handle here */
		return FALSE;
	}

	CloseHandle (done_event);
	return TRUE;
#else
	/* We don't support domain finalization without a GC */
	return FALSE;
#endif
}

void
ves_icall_System_GC_InternalCollect (int generation)
{
	mono_gc_collect (generation);
}

gint64
ves_icall_System_GC_GetTotalMemory (MonoBoolean forceCollection)
{
	MONO_ARCH_SAVE_REGS;

	if (forceCollection)
		mono_gc_collect (mono_gc_max_generation ());
	return mono_gc_get_used_size ();
}

void
ves_icall_System_GC_KeepAlive (MonoObject *obj)
{
	MONO_ARCH_SAVE_REGS;

	/*
	 * Does nothing.
	 */
}

void
ves_icall_System_GC_ReRegisterForFinalize (MonoObject *obj)
{
	MONO_ARCH_SAVE_REGS;

	object_register_finalizer (obj, run_finalize);
}

void
ves_icall_System_GC_SuppressFinalize (MonoObject *obj)
{
	MONO_ARCH_SAVE_REGS;

	object_register_finalizer (obj, NULL);
}

void
ves_icall_System_GC_WaitForPendingFinalizers (void)
{
	MONO_ARCH_SAVE_REGS;
	
#ifndef HAVE_NULL_GC
	if (!mono_gc_pending_finalizers ())
		return;

	if (mono_thread_current () == gc_thread)
		/* Avoid deadlocks */
		return;

	ResetEvent (pending_done_event);
	mono_gc_finalize_notify ();
	/* g_print ("Waiting for pending finalizers....\n"); */
	WaitForSingleObjectEx (pending_done_event, INFINITE, TRUE);
	/* g_print ("Done pending....\n"); */
#else
#endif
}
#define mono_allocator_lock() EnterCriticalSection (&allocator_section)
#define mono_allocator_unlock() LeaveCriticalSection (&allocator_section)
static CRITICAL_SECTION allocator_section;
static CRITICAL_SECTION handle_section;

typedef enum {
	HANDLE_WEAK,
	HANDLE_WEAK_TRACK,
	HANDLE_NORMAL,
	HANDLE_PINNED
} HandleType;

static void mono_gchandle_set_target (guint32 gchandle, MonoObject *obj);

MonoObject *
ves_icall_System_GCHandle_GetTarget (guint32 handle)
{
	return mono_gchandle_get_target (handle);
}

/*
 * if type == -1, change the target of the handle, otherwise allocate a new handle.
 */
guint32
ves_icall_System_GCHandle_GetTargetHandle (MonoObject *obj, guint32 handle, gint32 type)
{
	if (type == -1) {
		mono_gchandle_set_target (handle, obj);
		/* the handle doesn't change */
		return handle;
	}
	switch (type) {
	case HANDLE_WEAK:
		return mono_gchandle_new_weakref (obj, FALSE);
	case HANDLE_WEAK_TRACK:
		return mono_gchandle_new_weakref (obj, TRUE);
	case HANDLE_NORMAL:
		return mono_gchandle_new (obj, FALSE);
	case HANDLE_PINNED:
		return mono_gchandle_new (obj, TRUE);
	default:
		g_assert_not_reached ();
	}
	return 0;
}

void
ves_icall_System_GCHandle_FreeHandle (guint32 handle)
{
	mono_gchandle_free (handle);
}

gpointer
ves_icall_System_GCHandle_GetAddrOfPinnedObject (guint32 handle)
{
	MonoObject *obj;

	obj = mono_gchandle_get_target (handle);
	if (obj) {
		MonoClass *klass = mono_object_class (obj);
		if (klass == mono_defaults.string_class) {
			return mono_string_chars ((MonoString*)obj);
		} else if (klass->rank) {
			return mono_array_addr ((MonoArray*)obj, char, 0);
		} else {
			/* the C# code will check and throw the exception */
			/* FIXME: missing !klass->blittable test, see bug #61134 */
			if ((klass->flags & TYPE_ATTRIBUTE_LAYOUT_MASK) == TYPE_ATTRIBUTE_AUTO_LAYOUT)
				return (gpointer)-1;
			return (char*)obj + sizeof (MonoObject);
		}
	}
	return NULL;
}

typedef struct {
	guint32  *bitmap;
	gpointer *entries;
	guint32   size;
	guint8    type;
	guint     slot_hint : 24; /* starting slot for search */
	/* 2^16 appdomains should be enough for everyone (though I know I'll regret this in 20 years) */
	/* we alloc this only for weak refs, since we can get the domain directly in the other cases */
	guint16  *domain_ids;
} HandleData;

/* weak and weak-track arrays will be allocated in malloc memory 
 */
static HandleData gc_handles [] = {
	{NULL, NULL, 0, HANDLE_WEAK, 0},
	{NULL, NULL, 0, HANDLE_WEAK_TRACK, 0},
	{NULL, NULL, 0, HANDLE_NORMAL, 0},
	{NULL, NULL, 0, HANDLE_PINNED, 0}
};

#define lock_handles(handles) EnterCriticalSection (&handle_section)
#define unlock_handles(handles) LeaveCriticalSection (&handle_section)

static int
find_first_unset (guint32 bitmap)
{
	int i;
	for (i = 0; i < 32; ++i) {
		if (!(bitmap & (1 << i)))
			return i;
	}
	return -1;
}

static guint32
alloc_handle (HandleData *handles, MonoObject *obj)
{
	gint slot, i;
	lock_handles (handles);
	if (!handles->size) {
		handles->size = 32;
		if (handles->type > HANDLE_WEAK_TRACK) {
			handles->entries = mono_gc_alloc_fixed (sizeof (gpointer) * handles->size, NULL);
		} else {
			handles->entries = g_malloc0 (sizeof (gpointer) * handles->size);
			handles->domain_ids = g_malloc0 (sizeof (guint16) * handles->size);
		}
		handles->bitmap = g_malloc0 (handles->size / 8);
	}
	i = -1;
	for (slot = handles->slot_hint; slot < handles->size / 32; ++slot) {
		if (handles->bitmap [slot] != 0xffffffff) {
			i = find_first_unset (handles->bitmap [slot]);
			handles->slot_hint = slot;
			break;
		}
	}
	if (i == -1 && handles->slot_hint != 0) {
		for (slot = 0; slot < handles->slot_hint; ++slot) {
			if (handles->bitmap [slot] != 0xffffffff) {
				i = find_first_unset (handles->bitmap [slot]);
				handles->slot_hint = slot;
				break;
			}
		}
	}
	if (i == -1) {
		guint32 *new_bitmap;
		guint32 new_size = handles->size * 2; /* always double: we memset to 0 based on this below */

		/* resize and copy the bitmap */
		new_bitmap = g_malloc0 (new_size / 8);
		memcpy (new_bitmap, handles->bitmap, handles->size / 8);
		g_free (handles->bitmap);
		handles->bitmap = new_bitmap;

		/* resize and copy the entries */
		if (handles->type > HANDLE_WEAK_TRACK) {
			gpointer *entries;
			entries = mono_gc_alloc_fixed (sizeof (gpointer) * new_size, NULL);
			memcpy (entries, handles->entries, sizeof (gpointer) * handles->size);
			handles->entries = entries;
		} else {
			gpointer *entries;
			guint16 *domain_ids;
			domain_ids = g_malloc0 (sizeof (guint16) * new_size);
			entries = g_malloc (sizeof (gpointer) * new_size);
			/* we disable GC because we could lose some disappearing link updates */
			mono_gc_disable ();
			memcpy (entries, handles->entries, sizeof (gpointer) * handles->size);
			memset (entries + handles->size, 0, sizeof (gpointer) * handles->size);
			memcpy (domain_ids, handles->domain_ids, sizeof (guint16) * handles->size);
			for (i = 0; i < handles->size; ++i) {
				MonoObject *obj = mono_gc_weak_link_get (&(handles->entries [i]));
				if (handles->entries [i])
					mono_gc_weak_link_remove (&(handles->entries [i]));
				/*g_print ("reg/unreg entry %d of type %d at %p to object %p (%p), was: %p\n", i, handles->type, &(entries [i]), obj, entries [i], handles->entries [i]);*/
				if (obj) {
					mono_gc_weak_link_add (&(entries [i]), obj);
				}
			}
			g_free (handles->entries);
			g_free (handles->domain_ids);
			handles->entries = entries;
			handles->domain_ids = domain_ids;
			mono_gc_enable ();
		}

		/* set i and slot to the next free position */
		i = 0;
		slot = (handles->size + 1) / 32;
		handles->slot_hint = handles->size + 1;
		handles->size = new_size;
	}
	handles->bitmap [slot] |= 1 << i;
	slot = slot * 32 + i;
	handles->entries [slot] = obj;
	if (handles->type <= HANDLE_WEAK_TRACK) {
		if (obj)
			mono_gc_weak_link_add (&(handles->entries [slot]), obj);
	}

	unlock_handles (handles);
	/*g_print ("allocated entry %d of type %d to object %p (in slot: %p)\n", slot, handles->type, obj, handles->entries [slot]);*/
	return (slot << 3) | (handles->type + 1);
}

/**
 * mono_gchandle_new:
 * @obj: managed object to get a handle for
 * @pinned: whether the object should be pinned
 *
 * This returns a handle that wraps the object, this is used to keep a
 * reference to a managed object from the unmanaged world and preventing the
 * object from being disposed.
 * 
 * If @pinned is false the address of the object can not be obtained, if it is
 * true the address of the object can be obtained.  This will also pin the
 * object so it will not be possible by a moving garbage collector to move the
 * object. 
 * 
 * Returns: a handle that can be used to access the object from
 * unmanaged code.
 */
guint32
mono_gchandle_new (MonoObject *obj, gboolean pinned)
{
	return alloc_handle (&gc_handles [pinned? HANDLE_PINNED: HANDLE_NORMAL], obj);
}

/**
 * mono_gchandle_new_weakref:
 * @obj: managed object to get a handle for
 * @pinned: whether the object should be pinned
 *
 * This returns a weak handle that wraps the object, this is used to
 * keep a reference to a managed object from the unmanaged world.
 * Unlike the mono_gchandle_new the object can be reclaimed by the
 * garbage collector.  In this case the value of the GCHandle will be
 * set to zero.
 * 
 * If @pinned is false the address of the object can not be obtained, if it is
 * true the address of the object can be obtained.  This will also pin the
 * object so it will not be possible by a moving garbage collector to move the
 * object. 
 * 
 * Returns: a handle that can be used to access the object from
 * unmanaged code.
 */
guint32
mono_gchandle_new_weakref (MonoObject *obj, gboolean track_resurrection)
{
	return alloc_handle (&gc_handles [track_resurrection? HANDLE_WEAK_TRACK: HANDLE_WEAK], obj);
}

/**
 * mono_gchandle_get_target:
 * @gchandle: a GCHandle's handle.
 *
 * The handle was previously created by calling mono_gchandle_new or
 * mono_gchandle_new_weakref. 
 *
 * Returns a pointer to the MonoObject represented by the handle or
 * NULL for a collected object if using a weakref handle.
 */
MonoObject*
mono_gchandle_get_target (guint32 gchandle)
{
	guint slot = gchandle >> 3;
	guint type = (gchandle & 7) - 1;
	HandleData *handles = &gc_handles [type];
	MonoObject *obj = NULL;
	if (type > 3)
		return NULL;
	lock_handles (handles);
	if (slot < handles->size && (handles->bitmap [slot / 32] & (1 << (slot % 32)))) {
		if (handles->type <= HANDLE_WEAK_TRACK) {
			obj = mono_gc_weak_link_get (&handles->entries [slot]);
		} else {
			obj = handles->entries [slot];
		}
	} else {
		/* print a warning? */
	}
	unlock_handles (handles);
	/*g_print ("get target of entry %d of type %d: %p\n", slot, handles->type, obj);*/
	return obj;
}

static void
mono_gchandle_set_target (guint32 gchandle, MonoObject *obj)
{
	guint slot = gchandle >> 3;
	guint type = (gchandle & 7) - 1;
	HandleData *handles = &gc_handles [type];
	if (type > 3)
		return;
	lock_handles (handles);
	if (slot < handles->size && (handles->bitmap [slot / 32] & (1 << (slot % 32)))) {
		if (handles->type <= HANDLE_WEAK_TRACK) {
			if (handles->entries [slot])
				mono_gc_weak_link_remove (&handles->entries [slot]);
			if (obj)
				mono_gc_weak_link_add (&handles->entries [slot], obj);
		} else {
			handles->entries [slot] = obj;
		}
	} else {
		/* print a warning? */
	}
	/*g_print ("changed entry %d of type %d to object %p (in slot: %p)\n", slot, handles->type, obj, handles->entries [slot]);*/
	unlock_handles (handles);
}

/**
 * mono_gchandle_is_in_domain:
 * @gchandle: a GCHandle's handle.
 * @domain: An application domain.
 *
 * Returns: true if the object wrapped by the @gchandle belongs to the specific @domain.
 */
gboolean
mono_gchandle_is_in_domain (guint32 gchandle, MonoDomain *domain)
{
	guint slot = gchandle >> 3;
	guint type = (gchandle & 7) - 1;
	HandleData *handles = &gc_handles [type];
	gboolean result = FALSE;
	if (type > 3)
		return FALSE;
	lock_handles (handles);
	if (slot < handles->size && (handles->bitmap [slot / 32] & (1 << (slot % 32)))) {
		if (handles->type <= HANDLE_WEAK_TRACK) {
			result = domain->domain_id == handles->domain_ids [slot];
		} else {
			MonoObject *obj;
			obj = handles->entries [slot];
			if (obj == NULL)
				result = TRUE;
			else
				result = domain == mono_object_domain (obj);
		}
	} else {
		/* print a warning? */
	}
	unlock_handles (handles);
	return result;
}

/**
 * mono_gchandle_free:
 * @gchandle: a GCHandle's handle.
 *
 * Frees the @gchandle handle.  If there are no outstanding
 * references, the garbage collector can reclaim the memory of the
 * object wrapped. 
 */
void
mono_gchandle_free (guint32 gchandle)
{
	guint slot = gchandle >> 3;
	guint type = (gchandle & 7) - 1;
	HandleData *handles = &gc_handles [type];
	if (type > 3)
		return;
	lock_handles (handles);
	if (slot < handles->size && (handles->bitmap [slot / 32] & (1 << (slot % 32)))) {
		if (handles->type <= HANDLE_WEAK_TRACK) {
			if (handles->entries [slot])
				mono_gc_weak_link_remove (&handles->entries [slot]);
		} else {
			handles->entries [slot] = NULL;
		}
		handles->bitmap [slot / 32] &= ~(1 << (slot % 32));
	} else {
		/* print a warning? */
	}
	/*g_print ("freed entry %d of type %d\n", slot, handles->type);*/
	unlock_handles (handles);
}

#ifndef HAVE_NULL_GC

static HANDLE finalizer_event;
static volatile gboolean finished=FALSE;

void
mono_gc_finalize_notify (void)
{
#ifdef DEBUG
	g_message (G_GNUC_PRETTY_FUNCTION ": prodding finalizer");
#endif

	SetEvent (finalizer_event);
}

static void
collect_objects (gpointer key, gpointer value, gpointer user_data)
{
	GPtrArray *arr = (GPtrArray*)user_data;
	g_ptr_array_add (arr, key);
}

/*
 * finalize_domain_objects:
 *
 *  Run the finalizers of all finalizable objects in req->domain.
 */
static void
finalize_domain_objects (DomainFinalizationReq *req)
{
	int i;
	GPtrArray *objs;
	MonoDomain *domain = req->domain;
	
	while (g_hash_table_size (domain->finalizable_objects_hash) > 0) {
		/* 
		 * Since the domain is unloading, nobody is allowed to put
		 * new entries into the hash table. But finalize_object might
		 * remove entries from the hash table, so we make a copy.
		 */
		objs = g_ptr_array_new ();
		g_hash_table_foreach (domain->finalizable_objects_hash, 
							  collect_objects, objs);
		/* printf ("FINALIZING %d OBJECTS.\n", objs->len); */

		for (i = 0; i < objs->len; ++i) {
			MonoObject *o = (MonoObject*)g_ptr_array_index (objs, i);
			/* FIXME: Avoid finalizing threads, etc */
			run_finalize (o, 0);
		}

		g_ptr_array_free (objs, TRUE);
	}

	/* Process finalizers which are already in the queue */
	mono_gc_invoke_finalizers ();

	/* printf ("DONE.\n"); */
	SetEvent (req->done_event);

	/* The event is closed in mono_domain_finalize if we get here */
	g_free (req);
}

static guint32 finalizer_thread (gpointer unused)
{
	gc_thread = mono_thread_current ();

	SetEvent (thread_started_event);

	while(!finished) {
		/* Wait to be notified that there's at least one
		 * finaliser to run
		 */
		WaitForSingleObjectEx (finalizer_event, INFINITE, TRUE);

		if (domains_to_finalize) {
			mono_finalizer_lock ();
			if (domains_to_finalize) {
				DomainFinalizationReq *req = domains_to_finalize->data;
				domains_to_finalize = g_slist_remove (domains_to_finalize, req);
				mono_finalizer_unlock ();

				finalize_domain_objects (req);
			}
			else
				mono_finalizer_unlock ();
		}				

#ifdef DEBUG
		g_message (G_GNUC_PRETTY_FUNCTION ": invoking finalizers");
#endif

		/* If finished == TRUE, mono_gc_cleanup has been called (from mono_runtime_cleanup),
		 * before the domain is unloaded.
		 */
		mono_gc_invoke_finalizers ();

		SetEvent (pending_done_event);
	}

	SetEvent (shutdown_event);
	return(0);
}

/* 
 * Enable or disable the separate finalizer thread.
 * It's currently disabled because it still requires some
 * work in the rest of the runtime.
 */
#define ENABLE_FINALIZER_THREAD

void
mono_gc_init (void)
{
	InitializeCriticalSection (&handle_section);
	InitializeCriticalSection (&allocator_section);

	InitializeCriticalSection (&finalizer_mutex);

	MONO_GC_REGISTER_ROOT (gc_handles [HANDLE_NORMAL].entries);
	MONO_GC_REGISTER_ROOT (gc_handles [HANDLE_PINNED].entries);

	mono_gc_base_init ();

#ifdef ENABLE_FINALIZER_THREAD

	if (g_getenv ("GC_DONT_GC")) {
		gc_disabled = TRUE;
		return;
	}
	
	finalizer_event = CreateEvent (NULL, FALSE, FALSE, NULL);
	pending_done_event = CreateEvent (NULL, TRUE, FALSE, NULL);
	shutdown_event = CreateEvent (NULL, TRUE, FALSE, NULL);
	thread_started_event = CreateEvent (NULL, TRUE, FALSE, NULL);
	if (finalizer_event == NULL || pending_done_event == NULL || shutdown_event == NULL || thread_started_event == NULL) {
		g_assert_not_reached ();
	}

	mono_thread_create (mono_domain_get (), finalizer_thread, NULL);
	/*
	 * Wait until the finalizer thread sets gc_thread since its value is needed
	 * by mono_thread_attach ()
	 */
	WaitForSingleObjectEx (thread_started_event, INFINITE, FALSE);
#endif
}

void mono_gc_cleanup (void)
{
#ifdef DEBUG
	g_message (G_GNUC_PRETTY_FUNCTION ": cleaning up finalizer");
#endif

#ifdef ENABLE_FINALIZER_THREAD
	if (!gc_disabled) {
		ResetEvent (shutdown_event);
		finished = TRUE;
		if (mono_thread_current () != gc_thread) {
			mono_gc_finalize_notify ();
			/* Finishing the finalizer thread, so wait a little bit... */
			/* MS seems to wait for about 2 seconds */
			if (WaitForSingleObjectEx (shutdown_event, 2000, FALSE) == WAIT_TIMEOUT) {
				mono_thread_stop (gc_thread);
			}
		}
		gc_thread = NULL;
#ifdef HAVE_BOEHM_GC
		GC_finalizer_notifier = NULL;
#endif
	}

#endif

	DeleteCriticalSection (&handle_section);
	DeleteCriticalSection (&allocator_section);
	DeleteCriticalSection (&finalizer_mutex);
}

#else

/* no Boehm GC support. */
void mono_gc_init (void)
{
	InitializeCriticalSection (&handle_section);
}

void mono_gc_cleanup (void)
{
}

#endif

/**
 * mono_gc_is_finalizer_thread:
 * @thread: the thread to test.
 *
 * In Mono objects are finalized asynchronously on a separate thread.
 * This routine tests whether the @thread argument represents the
 * finalization thread.
 * 
 * Returns true if @thread is the finalization thread.
 */
gboolean
mono_gc_is_finalizer_thread (MonoThread *thread)
{
	return thread == gc_thread;
}