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.
72 const MonoObjectHandle mono_null_value_handle = NULL;
74 #define THIS_IS_AN_OK_NUMBER_OF_HANDLES 100
76 static HandleChunkElem*
77 chunk_element (HandleChunk *chunk, int idx)
79 return &chunk->elems[idx];
82 static HandleChunkElem*
83 handle_to_chunk_element (MonoObjectHandle o)
85 return (HandleChunkElem*)o;
88 /* Given a HandleChunkElem* search through the current handle stack to find its chunk and offset. */
90 chunk_element_to_chunk_idx (HandleStack *stack, HandleChunkElem *elem, int *out_idx)
92 HandleChunk *top = stack->top;
93 HandleChunk *cur = stack->bottom;
98 HandleChunkElem *front = &cur->elems [0];
99 HandleChunkElem *back = &cur->elems [cur->size];
101 if (front <= elem && elem < back) {
102 *out_idx = (int)(elem - front);
107 break; /* didn't find it. */
113 #ifdef MONO_HANDLE_TRACK_OWNER
114 #define SET_OWNER(chunk,idx) do { (chunk)->elems[(idx)].owner = owner; } while (0)
116 #define SET_OWNER(chunk,idx) do { } while (0)
119 #ifdef MONO_HANDLE_TRACK_SP
120 #define SET_SP(handles,chunk,idx) do { (chunk)->elems[(idx)].alloc_sp = handles->stackmark_sp; } while (0)
122 #define SET_SP(handles,chunk,idx) do { } while (0)
125 #ifdef MONO_HANDLE_TRACK_SP
127 mono_handle_chunk_leak_check (HandleStack *handles) {
128 if (handles->stackmark_sp) {
129 /* walk back from the top to the topmost non-empty chunk */
130 HandleChunk *c = handles->top;
131 while (c && c->size <= 0 && c != handles->bottom) {
134 if (c == NULL || c->size == 0)
136 g_assert (c && c->size > 0);
137 HandleChunkElem *e = chunk_element (c, c->size - 1);
138 if (e->alloc_sp < handles->stackmark_sp) {
139 /* If we get here, the topmost object on the handle stack was
140 * allocated from a function that is deeper in the call stack than
141 * the most recent HANDLE_FUNCTION_ENTER. That means it was
142 * probably not wrapped in a HANDLE_FUNCTION_ENTER/_RETURN pair
143 * and will never be reclaimed. */
144 g_warning ("Handle %p (object = %p) (allocated from \"%s\") is leaking.\n", e, e->o,
145 #ifdef MONO_HANDLE_TRACK_OWNER
156 /* Actual handles implementation */
158 #ifndef MONO_HANDLE_TRACK_OWNER
159 mono_handle_new (MonoObject *obj)
161 mono_handle_new (MonoObject *obj, const char *owner)
164 MonoThreadInfo *info = mono_thread_info_current ();
165 HandleStack *handles = (HandleStack *)info->handle_stack;
166 HandleChunk *top = handles->top;
167 #ifdef MONO_HANDLE_TRACK_SP
168 mono_handle_chunk_leak_check (handles);
172 if (G_LIKELY (top->size < OBJECTS_PER_HANDLES_CHUNK)) {
174 gpointer* objslot = &top->elems [idx].o;
175 /* can be interrupted anywhere here, so:
176 * 1. make sure the new slot is null
177 * 2. make the new slot scannable (increment size)
178 * 3. put a valid object in there
180 * (have to do 1 then 3 so that if we're interrupted
181 * between 1 and 2, the object is still live)
184 mono_memory_write_barrier ();
186 mono_memory_write_barrier ();
189 SET_SP (handles, top, idx);
192 if (G_LIKELY (top->next)) {
194 /* make sure size == 0 is visible to a GC thread before it sees the new top */
195 mono_memory_write_barrier ();
200 HandleChunk *new_chunk = g_new (HandleChunk, 1);
202 new_chunk->prev = top;
203 new_chunk->next = NULL;
204 /* make sure size == 0 before new chunk is visible */
205 mono_memory_write_barrier ();
206 top->next = new_chunk;
207 handles->top = new_chunk;
212 #ifndef MONO_HANDLE_TRACK_OWNER
213 mono_handle_new_interior (gpointer rawptr)
215 mono_handle_new_interior (gpointer rawptr, const char *owner)
218 MonoThreadInfo *info = mono_thread_info_current ();
219 HandleStack *handles = (HandleStack *)info->handle_stack;
220 HandleChunk *top = handles->interior;
221 #ifdef MONO_HANDLE_TRACK_SP
222 mono_handle_chunk_leak_check (handles);
228 * Don't extend the chunk now, interior handles are
229 * only used for icall arguments, they shouldn't
232 g_assert (top->size < OBJECTS_PER_HANDLES_CHUNK);
234 gpointer *objslot = &top->elems [idx].o;
236 mono_memory_write_barrier ();
238 mono_memory_write_barrier ();
241 SET_SP (handles, top, idx);
246 mono_handle_stack_alloc (void)
248 HandleStack *stack = g_new0 (HandleStack, 1);
249 HandleChunk *chunk = g_new0 (HandleChunk, 1);
250 HandleChunk *interior = g_new0 (HandleChunk, 1);
252 mono_memory_write_barrier ();
253 stack->top = stack->bottom = chunk;
254 stack->interior = interior;
255 #ifdef MONO_HANDLE_TRACK_SP
256 stack->stackmark_sp = NULL;
262 mono_handle_stack_free (HandleStack *stack)
266 HandleChunk *c = stack->bottom;
267 stack->top = stack->bottom = NULL;
268 mono_memory_write_barrier ();
270 HandleChunk *next = c->next;
275 g_free (stack->interior);
280 mono_handle_stack_free_domain (HandleStack *stack, MonoDomain *domain)
282 /* Called by the GC while clearing out objects of the given domain from the heap. */
283 /* If there are no handles-related bugs, there is nothing to do: if a
284 * thread accessed objects from the domain it was aborted, so any
285 * threads left alive cannot have any handles that point into the
286 * unloading domain. However if there is a handle leak, the handle stack is not */
289 /* Root domain only unloaded when mono is shutting down, don't need to check anything */
290 if (domain == mono_get_root_domain () || mono_runtime_is_shutting_down ())
292 HandleChunk *cur = stack->bottom;
293 HandleChunk *last = stack->top;
297 for (int idx = 0; idx < cur->size; ++idx) {
298 HandleChunkElem *elem = &cur->elems[idx];
301 g_assert (mono_object_domain (elem->o) != domain);
307 /* We don't examine the interior pointers here because the GC treats
308 * them conservatively and anyway we don't have enough information here to
309 * find the object's vtable.
314 check_handle_stack_monotonic (HandleStack *stack)
316 /* check that every allocated handle in the current handle stack is at no higher in the native stack than its predecessors */
317 #ifdef MONO_HANDLE_TRACK_SP
318 HandleChunk *cur = stack->bottom;
319 HandleChunk *last = stack->top;
322 HandleChunkElem *prev = NULL;
323 gboolean monotonic = TRUE;
325 for (int i = 0;i < cur->size; ++i) {
326 HandleChunkElem *elem = chunk_element (cur, i);
327 if (prev && elem->alloc_sp < prev->alloc_sp) {
329 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,
330 #ifdef MONO_HANDLE_TRACK_OWNER
346 g_assert (monotonic);
351 mono_handle_stack_scan (HandleStack *stack, GcScanFunc func, gpointer gc_data, gboolean precise)
353 if (precise) /* run just once (per handle stack) per GC */
354 check_handle_stack_monotonic (stack);
356 We're called twice - on the imprecise pass we call func to pin the
357 objects where the handle points to its interior. On the precise
358 pass, we scan all the objects where the handles point to the start of
361 Note that if we're running, we know the world is stopped.
364 HandleChunk *cur = stack->bottom;
365 HandleChunk *last = stack->top;
368 for (int i = 0; i < cur->size; ++i) {
369 HandleChunkElem* elem = chunk_element (cur, i);
370 gpointer* obj_slot = &elem->o;
371 if (*obj_slot != NULL)
372 func (obj_slot, gc_data);
379 HandleChunk *cur = stack->interior;
383 for (int i = 0; i < cur->size; ++i) {
384 HandleChunkElem* elem = chunk_element (cur, i);
385 gpointer* ptr_slot = &elem->o;
386 if (*ptr_slot != NULL)
387 func (ptr_slot, gc_data);
393 mono_stack_mark_record_size (MonoThreadInfo *info, HandleStackMark *stackmark, const char *func_name)
395 HandleStack *handles = (HandleStack *)info->handle_stack;
396 HandleChunk *cur = stackmark->chunk;
397 int size = -stackmark->size; //discard the starting point of the stack
400 if (cur == handles->top)
405 if (size > THIS_IS_AN_OK_NUMBER_OF_HANDLES)
406 g_warning ("%s USED %d handles\n", func_name, size);
410 * Pop the stack until @stackmark and make @value the top value.
412 * @return the new handle for what @value points to
415 mono_stack_mark_pop_value (MonoThreadInfo *info, HandleStackMark *stackmark, MonoRawHandle value)
417 MonoObject *obj = value ? *((MonoObject**)value) : NULL;
418 mono_stack_mark_pop (info, stackmark);
419 #ifndef MONO_HANDLE_TRACK_OWNER
420 return mono_handle_new (obj);
422 return mono_handle_new (obj, "<mono_stack_mark_pop_value>");
426 /* Temporary place for some of the handle enabled wrapper functions*/
429 mono_string_new_handle (MonoDomain *domain, const char *data, MonoError *error)
431 return MONO_HANDLE_NEW (MonoString, mono_string_new_checked (domain, data, error));
435 mono_array_new_handle (MonoDomain *domain, MonoClass *eclass, uintptr_t n, MonoError *error)
437 return MONO_HANDLE_NEW (MonoArray, mono_array_new_checked (domain, eclass, n, error));
441 mono_array_new_full_handle (MonoDomain *domain, MonoClass *array_class, uintptr_t *lengths, intptr_t *lower_bounds, MonoError *error)
443 return MONO_HANDLE_NEW (MonoArray, mono_array_new_full_checked (domain, array_class, lengths, lower_bounds, error));
446 #ifdef ENABLE_CHECKED_BUILD
447 /* Checked build helpers */
449 mono_handle_verify (MonoRawHandle raw_handle)
456 mono_array_handle_length (MonoArrayHandle arr)
458 MONO_REQ_GC_UNSAFE_MODE;
460 return MONO_HANDLE_RAW (arr)->max_length;
464 mono_gchandle_from_handle (MonoObjectHandle handle, mono_bool pinned)
466 /* FIXME: chunk_element_to_chunk_idx does a linear search through the
467 * chunks and we only need it for the assert */
468 MonoThreadInfo *info = mono_thread_info_current ();
469 HandleStack *stack = (HandleStack*) info->handle_stack;
470 HandleChunkElem* elem = handle_to_chunk_element (handle);
472 HandleChunk *chunk = chunk_element_to_chunk_idx (stack, elem, &elem_idx);
473 /* gchandles cannot deal with interior pointers */
474 g_assert (chunk != NULL);
475 return mono_gchandle_new (MONO_HANDLE_RAW (handle), pinned);
479 mono_gchandle_get_target_handle (uint32_t gchandle)
481 return MONO_HANDLE_NEW (MonoObject, mono_gchandle_get_target (gchandle));
485 mono_array_handle_pin_with_size (MonoArrayHandle handle, int size, uintptr_t idx, uint32_t *gchandle)
487 g_assert (gchandle != NULL);
488 *gchandle = mono_gchandle_from_handle (MONO_HANDLE_CAST(MonoObject,handle), TRUE);
489 MonoArray *raw = MONO_HANDLE_RAW (handle);
490 return mono_array_addr_with_size (raw, size, idx);
494 mono_string_handle_pin_chars (MonoStringHandle handle, uint32_t *gchandle)
496 g_assert (gchandle != NULL);
497 *gchandle = mono_gchandle_from_handle (MONO_HANDLE_CAST (MonoObject, handle), TRUE);
498 MonoString *raw = MONO_HANDLE_RAW (handle);
499 return mono_string_chars (raw);
503 mono_array_handle_memcpy_refs (MonoArrayHandle dest, uintptr_t dest_idx, MonoArrayHandle src, uintptr_t src_idx, uintptr_t len)
505 mono_array_memcpy_refs (MONO_HANDLE_RAW (dest), dest_idx, MONO_HANDLE_RAW (src), src_idx, len);
509 mono_handle_stack_is_empty (HandleStack *stack)
511 return (stack->top == stack->bottom && stack->top->size == 0);