3 * Handle to object in native code
6 * - Ludovic Henry <ludovic@xamarin.com>
7 * - Aleksey Klieger <aleksey.klieger@xamarin.com>
8 * - Rodrigo Kumpera <kumpera@xamarin.com>
10 * Copyright 2016 Dot net foundation.
11 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
17 #include <mono/metadata/handle.h>
18 #include <mono/metadata/object-internals.h>
19 #include <mono/metadata/gc-internals.h>
20 #include <mono/utils/atomic.h>
21 #include <mono/utils/mono-lazy-init.h>
22 #include <mono/utils/mono-threads.h>
23 /* TODO (missing pieces)
28 mix/max/avg size of stack marks
31 Actually do something in mono_handle_verify
33 Shrink the handles stack in mono_handle_stack_scan
34 Properly report it to the profiler.
35 Add a boehm implementation
37 TODO (things to explore):
39 There's no convenient way to wrap the object allocation function.
41 MonoCultureInfoHandle culture = MONO_HANDLE_NEW (MonoCultureInfo, mono_object_new_checked (domain, klass, &error));
43 Maybe what we need is a round of cleanup around all exposed types in the runtime to unify all helpers under the same hoof.
44 Combine: MonoDefaults, GENERATE_GET_CLASS_WITH_CACHE, TYPED_HANDLE_DECL and friends.
45 This would solve the age old issue of making it clear which types are optional and tell that to the linker.
46 We could then generate neat type safe wrappers.
52 * If we are running with cooperative GC, all the handle stack
53 * manipulation will complete before a GC thread scans the handle
54 * stack. If we are using async suspend, however, a thread may be
55 * trying to allocate a new handle, or unwind the handle stack when
56 * the GC stops the world.
58 * In particular, we need to ensure that if the mutator thread is
59 * suspended while manipulating the handle stack, the stack is in a
60 * good enough state to be scanned. In particular, the size of each
61 * chunk should be updated before an object is written into the
62 * handle, and chunks to be scanned (between bottom and top) should
65 * Note that the handle stack is scanned PRECISELY (see
66 * sgen_client_scan_thread_data ()). That means there should not be
67 * stale objects scanned. So when we manipulate the size of a chunk,
68 * wemust ensure that the newly scannable slot is either null or
69 * points to a valid value.
76 return (HandleStack *)mono_gc_alloc_fixed (sizeof (HandleStack), MONO_GC_DESCRIPTOR_NULL, MONO_ROOT_SOURCE_HANDLE, "Thread Handle Stack");
80 free_handle_stack (HandleStack *stack)
82 mono_gc_free_fixed (stack);
88 return (HandleChunk *)GC_MALLOC (sizeof (HandleChunk));
92 free_handle_chunk (HandleChunk *chunk)
99 return g_new (HandleStack, 1);
103 free_handle_stack (HandleStack *stack)
111 return g_new (HandleChunk, 1);
115 free_handle_chunk (HandleChunk *chunk)
121 const MonoObjectHandle mono_null_value_handle = NULL;
123 #define THIS_IS_AN_OK_NUMBER_OF_HANDLES 100
125 static HandleChunkElem*
126 chunk_element (HandleChunk *chunk, int idx)
128 return &chunk->elems[idx];
131 static HandleChunkElem*
132 handle_to_chunk_element (MonoObjectHandle o)
134 return (HandleChunkElem*)o;
137 /* Given a HandleChunkElem* search through the current handle stack to find its chunk and offset. */
139 chunk_element_to_chunk_idx (HandleStack *stack, HandleChunkElem *elem, int *out_idx)
141 HandleChunk *top = stack->top;
142 HandleChunk *cur = stack->bottom;
146 while (cur != NULL) {
147 HandleChunkElem *front = &cur->elems [0];
148 HandleChunkElem *back = &cur->elems [cur->size];
150 if (front <= elem && elem < back) {
151 *out_idx = (int)(elem - front);
156 break; /* didn't find it. */
162 #ifdef MONO_HANDLE_TRACK_OWNER
163 #define SET_OWNER(chunk,idx) do { (chunk)->elems[(idx)].owner = owner; } while (0)
165 #define SET_OWNER(chunk,idx) do { } while (0)
168 #ifdef MONO_HANDLE_TRACK_SP
169 #define SET_SP(handles,chunk,idx) do { (chunk)->elems[(idx)].alloc_sp = handles->stackmark_sp; } while (0)
171 #define SET_SP(handles,chunk,idx) do { } while (0)
174 #ifdef MONO_HANDLE_TRACK_SP
176 mono_handle_chunk_leak_check (HandleStack *handles) {
177 if (handles->stackmark_sp) {
178 /* walk back from the top to the topmost non-empty chunk */
179 HandleChunk *c = handles->top;
180 while (c && c->size <= 0 && c != handles->bottom) {
183 if (c == NULL || c->size == 0)
185 g_assert (c && c->size > 0);
186 HandleChunkElem *e = chunk_element (c, c->size - 1);
187 if (e->alloc_sp < handles->stackmark_sp) {
188 /* If we get here, the topmost object on the handle stack was
189 * allocated from a function that is deeper in the call stack than
190 * the most recent HANDLE_FUNCTION_ENTER. That means it was
191 * probably not wrapped in a HANDLE_FUNCTION_ENTER/_RETURN pair
192 * and will never be reclaimed. */
193 g_warning ("Handle %p (object = %p) (allocated from \"%s\") is leaking.\n", e, e->o,
194 #ifdef MONO_HANDLE_TRACK_OWNER
205 /* Actual handles implementation */
207 #ifndef MONO_HANDLE_TRACK_OWNER
208 mono_handle_new (MonoObject *obj)
210 mono_handle_new (MonoObject *obj, const char *owner)
213 MonoThreadInfo *info = mono_thread_info_current ();
214 HandleStack *handles = (HandleStack *)info->handle_stack;
215 HandleChunk *top = handles->top;
216 #ifdef MONO_HANDLE_TRACK_SP
217 mono_handle_chunk_leak_check (handles);
221 if (G_LIKELY (top->size < OBJECTS_PER_HANDLES_CHUNK)) {
223 gpointer* objslot = &top->elems [idx].o;
224 /* can be interrupted anywhere here, so:
225 * 1. make sure the new slot is null
226 * 2. make the new slot scannable (increment size)
227 * 3. put a valid object in there
229 * (have to do 1 then 3 so that if we're interrupted
230 * between 1 and 2, the object is still live)
233 mono_memory_write_barrier ();
235 mono_memory_write_barrier ();
238 SET_SP (handles, top, idx);
241 if (G_LIKELY (top->next)) {
243 /* make sure size == 0 is visible to a GC thread before it sees the new top */
244 mono_memory_write_barrier ();
249 HandleChunk *new_chunk = new_handle_chunk ();
251 new_chunk->prev = top;
252 new_chunk->next = NULL;
253 /* make sure size == 0 before new chunk is visible */
254 mono_memory_write_barrier ();
255 top->next = new_chunk;
256 handles->top = new_chunk;
261 #ifndef MONO_HANDLE_TRACK_OWNER
262 mono_handle_new_interior (gpointer rawptr)
264 mono_handle_new_interior (gpointer rawptr, const char *owner)
267 MonoThreadInfo *info = mono_thread_info_current ();
268 HandleStack *handles = (HandleStack *)info->handle_stack;
269 HandleChunk *top = handles->interior;
270 #ifdef MONO_HANDLE_TRACK_SP
271 mono_handle_chunk_leak_check (handles);
277 * Don't extend the chunk now, interior handles are
278 * only used for icall arguments, they shouldn't
281 g_assert (top->size < OBJECTS_PER_HANDLES_CHUNK);
283 gpointer *objslot = &top->elems [idx].o;
285 mono_memory_write_barrier ();
287 mono_memory_write_barrier ();
290 SET_SP (handles, top, idx);
295 mono_handle_stack_alloc (void)
297 HandleStack *stack = new_handle_stack ();
298 HandleChunk *chunk = new_handle_chunk ();
299 HandleChunk *interior = new_handle_chunk ();
301 chunk->prev = chunk->next = NULL;
303 interior->prev = interior->next = NULL;
305 mono_memory_write_barrier ();
306 stack->top = stack->bottom = chunk;
307 stack->interior = interior;
308 #ifdef MONO_HANDLE_TRACK_SP
309 stack->stackmark_sp = NULL;
315 mono_handle_stack_free (HandleStack *stack)
319 HandleChunk *c = stack->bottom;
320 stack->top = stack->bottom = NULL;
321 mono_memory_write_barrier ();
323 HandleChunk *next = c->next;
324 free_handle_chunk (c);
327 free_handle_chunk (c);
328 free_handle_chunk (stack->interior);
329 free_handle_stack (stack);
333 mono_handle_stack_free_domain (HandleStack *stack, MonoDomain *domain)
335 /* Called by the GC while clearing out objects of the given domain from the heap. */
336 /* If there are no handles-related bugs, there is nothing to do: if a
337 * thread accessed objects from the domain it was aborted, so any
338 * threads left alive cannot have any handles that point into the
339 * unloading domain. However if there is a handle leak, the handle stack is not */
342 /* Root domain only unloaded when mono is shutting down, don't need to check anything */
343 if (domain == mono_get_root_domain () || mono_runtime_is_shutting_down ())
345 HandleChunk *cur = stack->bottom;
346 HandleChunk *last = stack->top;
350 for (int idx = 0; idx < cur->size; ++idx) {
351 HandleChunkElem *elem = &cur->elems[idx];
354 g_assert (mono_object_domain (elem->o) != domain);
360 /* We don't examine the interior pointers here because the GC treats
361 * them conservatively and anyway we don't have enough information here to
362 * find the object's vtable.
367 check_handle_stack_monotonic (HandleStack *stack)
369 /* check that every allocated handle in the current handle stack is at no higher in the native stack than its predecessors */
370 #ifdef MONO_HANDLE_TRACK_SP
371 HandleChunk *cur = stack->bottom;
372 HandleChunk *last = stack->top;
375 HandleChunkElem *prev = NULL;
376 gboolean monotonic = TRUE;
378 for (int i = 0;i < cur->size; ++i) {
379 HandleChunkElem *elem = chunk_element (cur, i);
380 if (prev && elem->alloc_sp < prev->alloc_sp) {
382 g_warning ("Handle %p (object %p) (allocated from \"%s\") is was allocated deeper in the call stack than its successor (allocated from \"%s\").", prev, prev->o,
383 #ifdef MONO_HANDLE_TRACK_OWNER
399 g_assert (monotonic);
404 mono_handle_stack_scan (HandleStack *stack, GcScanFunc func, gpointer gc_data, gboolean precise)
406 if (precise) /* run just once (per handle stack) per GC */
407 check_handle_stack_monotonic (stack);
409 We're called twice - on the imprecise pass we call func to pin the
410 objects where the handle points to its interior. On the precise
411 pass, we scan all the objects where the handles point to the start of
414 Note that if we're running, we know the world is stopped.
417 HandleChunk *cur = stack->bottom;
418 HandleChunk *last = stack->top;
421 for (int i = 0; i < cur->size; ++i) {
422 HandleChunkElem* elem = chunk_element (cur, i);
423 gpointer* obj_slot = &elem->o;
424 if (*obj_slot != NULL)
425 func (obj_slot, gc_data);
432 HandleChunk *cur = stack->interior;
436 for (int i = 0; i < cur->size; ++i) {
437 HandleChunkElem* elem = chunk_element (cur, i);
438 gpointer* ptr_slot = &elem->o;
439 if (*ptr_slot != NULL)
440 func (ptr_slot, gc_data);
446 mono_stack_mark_record_size (MonoThreadInfo *info, HandleStackMark *stackmark, const char *func_name)
448 HandleStack *handles = (HandleStack *)info->handle_stack;
449 HandleChunk *cur = stackmark->chunk;
450 int size = -stackmark->size; //discard the starting point of the stack
453 if (cur == handles->top)
458 if (size > THIS_IS_AN_OK_NUMBER_OF_HANDLES)
459 g_warning ("%s USED %d handles\n", func_name, size);
463 * Pop the stack until @stackmark and make @value the top value.
465 * @return the new handle for what @value points to
468 mono_stack_mark_pop_value (MonoThreadInfo *info, HandleStackMark *stackmark, MonoRawHandle value)
470 MonoObject *obj = value ? *((MonoObject**)value) : NULL;
471 mono_stack_mark_pop (info, stackmark);
472 #ifndef MONO_HANDLE_TRACK_OWNER
473 return mono_handle_new (obj);
475 return mono_handle_new (obj, "<mono_stack_mark_pop_value>");
479 /* Temporary place for some of the handle enabled wrapper functions*/
482 mono_string_new_handle (MonoDomain *domain, const char *data, MonoError *error)
484 return MONO_HANDLE_NEW (MonoString, mono_string_new_checked (domain, data, error));
488 mono_array_new_handle (MonoDomain *domain, MonoClass *eclass, uintptr_t n, MonoError *error)
490 return MONO_HANDLE_NEW (MonoArray, mono_array_new_checked (domain, eclass, n, error));
494 mono_array_new_full_handle (MonoDomain *domain, MonoClass *array_class, uintptr_t *lengths, intptr_t *lower_bounds, MonoError *error)
496 return MONO_HANDLE_NEW (MonoArray, mono_array_new_full_checked (domain, array_class, lengths, lower_bounds, error));
499 #ifdef ENABLE_CHECKED_BUILD
500 /* Checked build helpers */
502 mono_handle_verify (MonoRawHandle raw_handle)
509 mono_array_handle_length (MonoArrayHandle arr)
511 MONO_REQ_GC_UNSAFE_MODE;
513 return MONO_HANDLE_RAW (arr)->max_length;
517 mono_gchandle_from_handle (MonoObjectHandle handle, mono_bool pinned)
519 /* FIXME: chunk_element_to_chunk_idx does a linear search through the
520 * chunks and we only need it for the assert */
521 MonoThreadInfo *info = mono_thread_info_current ();
522 HandleStack *stack = (HandleStack*) info->handle_stack;
523 HandleChunkElem* elem = handle_to_chunk_element (handle);
525 HandleChunk *chunk = chunk_element_to_chunk_idx (stack, elem, &elem_idx);
526 /* gchandles cannot deal with interior pointers */
527 g_assert (chunk != NULL);
528 return mono_gchandle_new (MONO_HANDLE_RAW (handle), pinned);
532 mono_gchandle_get_target_handle (uint32_t gchandle)
534 return MONO_HANDLE_NEW (MonoObject, mono_gchandle_get_target (gchandle));
538 mono_array_handle_pin_with_size (MonoArrayHandle handle, int size, uintptr_t idx, uint32_t *gchandle)
540 g_assert (gchandle != NULL);
541 *gchandle = mono_gchandle_from_handle (MONO_HANDLE_CAST(MonoObject,handle), TRUE);
542 MonoArray *raw = MONO_HANDLE_RAW (handle);
543 return mono_array_addr_with_size (raw, size, idx);
547 mono_string_handle_pin_chars (MonoStringHandle handle, uint32_t *gchandle)
549 g_assert (gchandle != NULL);
550 *gchandle = mono_gchandle_from_handle (MONO_HANDLE_CAST (MonoObject, handle), TRUE);
551 MonoString *raw = MONO_HANDLE_RAW (handle);
552 return mono_string_chars (raw);
556 mono_object_handle_pin_unbox (MonoObjectHandle obj, uint32_t *gchandle)
558 g_assert (!MONO_HANDLE_IS_NULL (obj));
559 MonoClass *klass = mono_handle_class (obj);
560 g_assert (klass->valuetype);
561 *gchandle = mono_gchandle_from_handle (obj, TRUE);
562 return mono_object_unbox (MONO_HANDLE_RAW (obj));
566 mono_array_handle_memcpy_refs (MonoArrayHandle dest, uintptr_t dest_idx, MonoArrayHandle src, uintptr_t src_idx, uintptr_t len)
568 mono_array_memcpy_refs (MONO_HANDLE_RAW (dest), dest_idx, MONO_HANDLE_RAW (src), src_idx, len);
572 mono_handle_stack_is_empty (HandleStack *stack)
574 return (stack->top == stack->bottom && stack->top->size == 0);