2 * sgen-fin-weak-hash.c: Finalizers and weak links.
5 * Paolo Molaro (lupus@ximian.com)
6 * Rodrigo Kumpera (kumpera@gmail.com)
8 * Copyright 2005-2011 Novell, Inc (http://www.novell.com)
9 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
10 * Copyright 2011 Xamarin, Inc.
11 * Copyright (C) 2012 Xamarin Inc
13 * This library is free software; you can redistribute it and/or
14 * modify it under the terms of the GNU Library General Public
15 * License 2.0 as published by the Free Software Foundation;
17 * This library is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * Library General Public License for more details.
22 * You should have received a copy of the GNU Library General Public
23 * License 2.0 along with this library; if not, write to the Free
24 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
30 #include "metadata/sgen-gc.h"
31 #include "metadata/sgen-gray.h"
32 #include "utils/dtrace.h"
34 #define ptr_in_nursery sgen_ptr_in_nursery
36 typedef SgenGrayQueue GrayQueue;
38 int num_ready_finalizers = 0;
39 static int no_finalize = 0;
41 #define DISLINK_OBJECT(l) (REVEAL_POINTER (*(void**)(l)))
42 #define DISLINK_TRACK(l) ((~(gulong)(*(void**)(l))) & 1)
45 * The finalizable hash has the object as the key, the
46 * disappearing_link hash, has the link address as key.
48 * Copyright 2011 Xamarin Inc.
51 #define TAG_MASK ((mword)0x1)
53 static inline MonoObject*
54 tagged_object_get_object (MonoObject *object)
56 return (MonoObject*)(((mword)object) & ~TAG_MASK);
60 tagged_object_get_tag (MonoObject *object)
62 return ((mword)object) & TAG_MASK;
65 static inline MonoObject*
66 tagged_object_apply (void *object, int tag_bits)
68 return (MonoObject*)((mword)object | (mword)tag_bits);
72 tagged_object_hash (MonoObject *o)
74 return mono_object_hash (tagged_object_get_object (o));
78 tagged_object_equals (MonoObject *a, MonoObject *b)
80 return tagged_object_get_object (a) == tagged_object_get_object (b);
83 static SgenHashTable minor_finalizable_hash = SGEN_HASH_TABLE_INIT (INTERNAL_MEM_FIN_TABLE, INTERNAL_MEM_FINALIZE_ENTRY, 0, (GHashFunc)tagged_object_hash, (GEqualFunc)tagged_object_equals);
84 static SgenHashTable major_finalizable_hash = SGEN_HASH_TABLE_INIT (INTERNAL_MEM_FIN_TABLE, INTERNAL_MEM_FINALIZE_ENTRY, 0, (GHashFunc)tagged_object_hash, (GEqualFunc)tagged_object_equals);
87 get_finalize_entry_hash_table (int generation)
90 case GENERATION_NURSERY: return &minor_finalizable_hash;
91 case GENERATION_OLD: return &major_finalizable_hash;
92 default: g_assert_not_reached ();
96 #define BRIDGE_OBJECT_MARKED 0x1
98 /* LOCKING: requires that the GC lock is held */
100 sgen_mark_bridge_object (MonoObject *obj)
102 SgenHashTable *hash_table = get_finalize_entry_hash_table (ptr_in_nursery (obj) ? GENERATION_NURSERY : GENERATION_OLD);
104 sgen_hash_table_set_key (hash_table, obj, tagged_object_apply (obj, BRIDGE_OBJECT_MARKED));
107 /* LOCKING: requires that the GC lock is held */
109 sgen_collect_bridge_objects (int generation, ScanCopyContext ctx)
111 CopyOrMarkObjectFunc copy_func = ctx.copy_func;
112 GrayQueue *queue = ctx.queue;
113 SgenHashTable *hash_table = get_finalize_entry_hash_table (generation);
121 SGEN_HASH_TABLE_FOREACH (hash_table, object, dummy) {
122 int tag = tagged_object_get_tag (object);
123 object = tagged_object_get_object (object);
125 /* Bridge code told us to ignore this one */
126 if (tag == BRIDGE_OBJECT_MARKED)
129 /* Object is a bridge object and major heap says it's dead */
130 if (major_collector.is_object_live ((char*)object))
133 /* Nursery says the object is dead. */
134 if (!sgen_gc_is_object_ready_for_finalization (object))
137 if (!sgen_is_bridge_object (object))
140 copy = (char*)object;
141 copy_func ((void**)©, queue);
143 sgen_bridge_register_finalized_object ((MonoObject*)copy);
145 if (hash_table == &minor_finalizable_hash && !ptr_in_nursery (copy)) {
146 /* remove from the list */
147 SGEN_HASH_TABLE_FOREACH_REMOVE (TRUE);
149 /* insert it into the major hash */
150 sgen_hash_table_replace (&major_finalizable_hash, tagged_object_apply (copy, tag), NULL, NULL);
152 SGEN_LOG (5, "Promoting finalization of object %p (%s) (was at %p) to major table", copy, sgen_safe_name (copy), object);
157 SGEN_LOG (5, "Updating object for finalization: %p (%s) (was at %p)", copy, sgen_safe_name (copy), object);
158 SGEN_HASH_TABLE_FOREACH_SET_KEY (tagged_object_apply (copy, tag));
160 } SGEN_HASH_TABLE_FOREACH_END;
164 /* LOCKING: requires that the GC lock is held */
166 sgen_finalize_in_range (int generation, ScanCopyContext ctx)
168 CopyOrMarkObjectFunc copy_func = ctx.copy_func;
169 GrayQueue *queue = ctx.queue;
170 SgenHashTable *hash_table = get_finalize_entry_hash_table (generation);
176 SGEN_HASH_TABLE_FOREACH (hash_table, object, dummy) {
177 int tag = tagged_object_get_tag (object);
178 object = tagged_object_get_object (object);
179 if (!major_collector.is_object_live ((char*)object)) {
180 gboolean is_fin_ready = sgen_gc_is_object_ready_for_finalization (object);
181 MonoObject *copy = object;
182 copy_func ((void**)©, queue);
184 /* remove and put in fin_ready_list */
185 SGEN_HASH_TABLE_FOREACH_REMOVE (TRUE);
186 num_ready_finalizers++;
187 sgen_queue_finalization_entry (copy);
188 /* Make it survive */
189 SGEN_LOG (5, "Queueing object for finalization: %p (%s) (was at %p) (%d/%d)", copy, sgen_safe_name (copy), object, num_ready_finalizers, sgen_hash_table_num_entries (hash_table));
192 if (hash_table == &minor_finalizable_hash && !ptr_in_nursery (copy)) {
193 /* remove from the list */
194 SGEN_HASH_TABLE_FOREACH_REMOVE (TRUE);
196 /* insert it into the major hash */
197 sgen_hash_table_replace (&major_finalizable_hash, tagged_object_apply (copy, tag), NULL, NULL);
199 SGEN_LOG (5, "Promoting finalization of object %p (%s) (was at %p) to major table", copy, sgen_safe_name (copy), object);
204 SGEN_LOG (5, "Updating object for finalization: %p (%s) (was at %p)", copy, sgen_safe_name (copy), object);
205 SGEN_HASH_TABLE_FOREACH_SET_KEY (tagged_object_apply (copy, tag));
209 } SGEN_HASH_TABLE_FOREACH_END;
212 /* LOCKING: requires that the GC lock is held */
214 register_for_finalization (MonoObject *obj, void *user_data, int generation)
216 SgenHashTable *hash_table = get_finalize_entry_hash_table (generation);
221 g_assert (user_data == NULL || user_data == mono_gc_run_finalize);
224 if (sgen_hash_table_replace (hash_table, obj, NULL, NULL))
225 SGEN_LOG (5, "Added finalizer for object: %p (%s) (%d) to %s table", obj, obj->vtable->klass->name, hash_table->num_entries, sgen_generation_name (generation));
227 if (sgen_hash_table_remove (hash_table, obj, NULL))
228 SGEN_LOG (5, "Removed finalizer for object: %p (%s) (%d)", obj, obj->vtable->klass->name, hash_table->num_entries);
232 #define STAGE_ENTRY_FREE 0
233 #define STAGE_ENTRY_BUSY 1
234 #define STAGE_ENTRY_USED 2
242 #define NUM_FIN_STAGE_ENTRIES 1024
244 static volatile gint32 next_fin_stage_entry = 0;
245 static StageEntry fin_stage_entries [NUM_FIN_STAGE_ENTRIES];
247 /* LOCKING: requires that the GC lock is held */
249 process_stage_entries (int num_entries, volatile gint32 *next_entry, StageEntry *entries, void (*process_func) (MonoObject*, void*))
252 int num_registered = 0;
255 for (i = 0; i < num_entries; ++i) {
256 gint32 state = entries [i].state;
258 if (state == STAGE_ENTRY_BUSY)
261 if (state != STAGE_ENTRY_USED ||
262 InterlockedCompareExchange (&entries [i].state, STAGE_ENTRY_BUSY, STAGE_ENTRY_USED) != STAGE_ENTRY_USED) {
266 process_func (entries [i].obj, entries [i].user_data);
268 entries [i].obj = NULL;
269 entries [i].user_data = NULL;
271 mono_memory_write_barrier ();
273 entries [i].state = STAGE_ENTRY_FREE;
280 /* g_print ("stage busy %d reg %d\n", num_busy, num_registered); */
284 add_stage_entry (int num_entries, volatile gint32 *next_entry, StageEntry *entries, MonoObject *obj, void *user_data)
291 if (index >= num_entries)
293 } while (InterlockedCompareExchange (next_entry, index + 1, index) != index);
296 * We don't need a write barrier here. *next_entry is just a
297 * help for finding an index, its value is irrelevant for
300 } while (entries [index].state != STAGE_ENTRY_FREE ||
301 InterlockedCompareExchange (&entries [index].state, STAGE_ENTRY_BUSY, STAGE_ENTRY_FREE) != STAGE_ENTRY_FREE);
303 entries [index].obj = obj;
304 entries [index].user_data = user_data;
306 mono_memory_write_barrier ();
308 entries [index].state = STAGE_ENTRY_USED;
313 /* LOCKING: requires that the GC lock is held */
315 process_fin_stage_entry (MonoObject *obj, void *user_data)
317 if (ptr_in_nursery (obj))
318 register_for_finalization (obj, user_data, GENERATION_NURSERY);
320 register_for_finalization (obj, user_data, GENERATION_OLD);
323 /* LOCKING: requires that the GC lock is held */
325 sgen_process_fin_stage_entries (void)
327 process_stage_entries (NUM_FIN_STAGE_ENTRIES, &next_fin_stage_entry, fin_stage_entries, process_fin_stage_entry);
331 mono_gc_register_for_finalization (MonoObject *obj, void *user_data)
333 while (!add_stage_entry (NUM_FIN_STAGE_ENTRIES, &next_fin_stage_entry, fin_stage_entries, obj, user_data)) {
335 sgen_process_fin_stage_entries ();
340 /* LOCKING: requires that the GC lock is held */
342 finalizers_for_domain (MonoDomain *domain, MonoObject **out_array, int out_size,
343 SgenHashTable *hash_table)
349 if (no_finalize || !out_size || !out_array)
352 SGEN_HASH_TABLE_FOREACH (hash_table, object, dummy) {
353 object = tagged_object_get_object (object);
355 if (mono_object_domain (object) == domain) {
356 /* remove and put in out_array */
357 SGEN_HASH_TABLE_FOREACH_REMOVE (TRUE);
358 out_array [count ++] = object;
359 SGEN_LOG (5, "Collecting object for finalization: %p (%s) (%d/%d)", object, sgen_safe_name (object), num_ready_finalizers, sgen_hash_table_num_entries (hash_table));
360 if (count == out_size)
364 } SGEN_HASH_TABLE_FOREACH_END;
369 * mono_gc_finalizers_for_domain:
370 * @domain: the unloading appdomain
371 * @out_array: output array
372 * @out_size: size of output array
374 * Store inside @out_array up to @out_size objects that belong to the unloading
375 * appdomain @domain. Returns the number of stored items. Can be called repeteadly
376 * until it returns 0.
377 * The items are removed from the finalizer data structure, so the caller is supposed
379 * @out_array should be on the stack to allow the GC to know the objects are still alive.
382 mono_gc_finalizers_for_domain (MonoDomain *domain, MonoObject **out_array, int out_size)
387 sgen_process_fin_stage_entries ();
388 result = finalizers_for_domain (domain, out_array, out_size, &minor_finalizable_hash);
389 if (result < out_size) {
390 result += finalizers_for_domain (domain, out_array + result, out_size - result,
391 &major_finalizable_hash);
398 static SgenHashTable minor_disappearing_link_hash = SGEN_HASH_TABLE_INIT (INTERNAL_MEM_DISLINK_TABLE, INTERNAL_MEM_DISLINK, 0, mono_aligned_addr_hash, NULL);
399 static SgenHashTable major_disappearing_link_hash = SGEN_HASH_TABLE_INIT (INTERNAL_MEM_DISLINK_TABLE, INTERNAL_MEM_DISLINK, 0, mono_aligned_addr_hash, NULL);
401 static SgenHashTable*
402 get_dislink_hash_table (int generation)
404 switch (generation) {
405 case GENERATION_NURSERY: return &minor_disappearing_link_hash;
406 case GENERATION_OLD: return &major_disappearing_link_hash;
407 default: g_assert_not_reached ();
411 /* LOCKING: assumes the GC lock is held */
413 add_or_remove_disappearing_link (MonoObject *obj, void **link, int generation)
415 SgenHashTable *hash_table = get_dislink_hash_table (generation);
418 if (sgen_hash_table_remove (hash_table, link, NULL)) {
419 SGEN_LOG (5, "Removed dislink %p (%d) from %s table",
420 link, hash_table->num_entries, sgen_generation_name (generation));
425 sgen_hash_table_replace (hash_table, link, NULL, NULL);
426 SGEN_LOG (5, "Added dislink for object: %p (%s) at %p to %s table",
427 obj, obj->vtable->klass->name, link, sgen_generation_name (generation));
430 /* LOCKING: requires that the GC lock is held */
432 sgen_null_link_in_range (int generation, gboolean before_finalization, ScanCopyContext ctx)
434 CopyOrMarkObjectFunc copy_func = ctx.copy_func;
435 GrayQueue *queue = ctx.queue;
438 SgenHashTable *hash = get_dislink_hash_table (generation);
440 SGEN_HASH_TABLE_FOREACH (hash, link, dummy) {
445 We null a weak link before unregistering it, so it's possible that a thread is
446 suspended right in between setting the content to null and staging the unregister.
448 The rest of this code cannot handle null links as DISLINK_OBJECT (NULL) produces an invalid address.
453 track = DISLINK_TRACK (link);
455 * Tracked references are processed after
456 * finalization handling whereas standard weak
457 * references are processed before. If an
458 * object is still not marked after finalization
459 * handling it means that it either doesn't have
460 * a finalizer or the finalizer has already run,
461 * so we must null a tracking reference.
463 if (track != before_finalization) {
464 object = DISLINK_OBJECT (link);
466 if (!major_collector.is_object_live (object)) {
467 if (sgen_gc_is_object_ready_for_finalization (object)) {
469 SGEN_LOG (5, "Dislink nullified at %p to GCed object %p", link, object);
470 SGEN_HASH_TABLE_FOREACH_REMOVE (TRUE);
474 copy_func ((void**)©, queue);
476 /* Update pointer if it's moved. If the object
477 * has been moved out of the nursery, we need to
478 * remove the link from the minor hash table to
481 * FIXME: what if an object is moved earlier?
484 if (hash == &minor_disappearing_link_hash && !ptr_in_nursery (copy)) {
485 SGEN_HASH_TABLE_FOREACH_REMOVE (TRUE);
488 *link = HIDE_POINTER (copy, track);
489 add_or_remove_disappearing_link ((MonoObject*)copy, link, GENERATION_OLD);
491 SGEN_LOG (5, "Upgraded dislink at %p to major because object %p moved to %p", link, object, copy);
495 *link = HIDE_POINTER (copy, track);
496 SGEN_LOG (5, "Updated dislink at %p to %p", link, DISLINK_OBJECT (link));
501 } SGEN_HASH_TABLE_FOREACH_END;
504 /* LOCKING: requires that the GC lock is held */
506 sgen_null_links_for_domain (MonoDomain *domain, int generation)
510 SgenHashTable *hash = get_dislink_hash_table (generation);
511 SGEN_HASH_TABLE_FOREACH (hash, link, dummy) {
512 char *object = DISLINK_OBJECT (link);
513 if (*link && object && !((MonoObject*)object)->vtable) {
514 gboolean free = TRUE;
520 * This can happen if finalizers are not ran, i.e. Environment.Exit ()
521 * is called from finalizer like in finalizer-abort.cs.
523 SGEN_LOG (5, "Disappearing link %p not freed", link);
526 SGEN_HASH_TABLE_FOREACH_REMOVE (free);
530 } SGEN_HASH_TABLE_FOREACH_END;
533 /* LOCKING: requires that the GC lock is held */
535 sgen_null_links_with_predicate (int generation, WeakLinkAlivePredicateFunc predicate, void *data)
539 SgenHashTable *hash = get_dislink_hash_table (generation);
540 SGEN_HASH_TABLE_FOREACH (hash, link, dummy) {
541 char *object = DISLINK_OBJECT (link);
546 is_alive = predicate ((MonoObject*)object, data);
550 SGEN_LOG (5, "Dislink nullified by predicate at %p to GCed object %p", link, object);
551 SGEN_HASH_TABLE_FOREACH_REMOVE (TRUE);
554 } SGEN_HASH_TABLE_FOREACH_END;
558 sgen_remove_finalizers_for_domain (MonoDomain *domain, int generation)
560 SgenHashTable *hash_table = get_finalize_entry_hash_table (generation);
564 SGEN_HASH_TABLE_FOREACH (hash_table, object, dummy) {
565 object = tagged_object_get_object (object);
567 if (mono_object_domain (object) == domain) {
568 SGEN_LOG (5, "Unregistering finalizer for object: %p (%s)", object, sgen_safe_name (object));
570 SGEN_HASH_TABLE_FOREACH_REMOVE (TRUE);
573 } SGEN_HASH_TABLE_FOREACH_END;
576 /* LOCKING: requires that the GC lock is held */
578 process_dislink_stage_entry (MonoObject *obj, void *_link)
582 add_or_remove_disappearing_link (NULL, link, GENERATION_NURSERY);
583 add_or_remove_disappearing_link (NULL, link, GENERATION_OLD);
585 if (ptr_in_nursery (obj))
586 add_or_remove_disappearing_link (obj, link, GENERATION_NURSERY);
588 add_or_remove_disappearing_link (obj, link, GENERATION_OLD);
592 #define NUM_DISLINK_STAGE_ENTRIES 1024
594 static volatile gint32 next_dislink_stage_entry = 0;
595 static StageEntry dislink_stage_entries [NUM_DISLINK_STAGE_ENTRIES];
597 /* LOCKING: requires that the GC lock is held */
599 sgen_process_dislink_stage_entries (void)
601 process_stage_entries (NUM_DISLINK_STAGE_ENTRIES, &next_dislink_stage_entry, dislink_stage_entries, process_dislink_stage_entry);
605 sgen_register_disappearing_link (MonoObject *obj, void **link, gboolean track, gboolean in_gc)
607 if (MONO_GC_WEAK_UPDATE_ENABLED ()) {
608 MonoVTable *vt = obj ? (MonoVTable*)SGEN_LOAD_VTABLE (obj) : NULL;
609 MONO_GC_WEAK_UPDATE ((mword)link,
610 *link ? (mword)DISLINK_OBJECT (link) : (mword)0,
612 obj ? (mword)sgen_safe_object_get_size (obj) : (mword)0,
613 obj ? vt->klass->name_space : NULL,
614 obj ? vt->klass->name : NULL,
619 *link = HIDE_POINTER (obj, track);
625 process_dislink_stage_entry (obj, link);
627 while (!add_stage_entry (NUM_DISLINK_STAGE_ENTRIES, &next_dislink_stage_entry, dislink_stage_entries, obj, link)) {
629 sgen_process_dislink_stage_entries ();
636 process_dislink_stage_entry (obj, link);
642 #endif /* HAVE_SGEN_GC */