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_OWNER
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 check_handle_stack_monotonic (HandleStack *stack)
282 /* check that every allocated handle in the current handle stack is at no higher in the native stack than its predecessors */
283 #ifdef MONO_HANDLE_TRACK_SP
284 HandleChunk *cur = stack->bottom;
285 HandleChunk *last = stack->top;
288 HandleChunkElem *prev = NULL;
289 gboolean monotonic = TRUE;
291 for (int i = 0;i < cur->size; ++i) {
292 HandleChunkElem *elem = chunk_element (cur, i);
293 if (prev && elem->alloc_sp < prev->alloc_sp) {
295 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,
296 #ifdef MONO_HANDLE_TRACK_OWNER
312 g_assert (monotonic);
317 mono_handle_stack_scan (HandleStack *stack, GcScanFunc func, gpointer gc_data, gboolean precise)
319 if (precise) /* run just once (per handle stack) per GC */
320 check_handle_stack_monotonic (stack);
322 We're called twice - on the imprecise pass we call func to pin the
323 objects where the handle points to its interior. On the precise
324 pass, we scan all the objects where the handles point to the start of
327 Note that if we're running, we know the world is stopped.
330 HandleChunk *cur = stack->bottom;
331 HandleChunk *last = stack->top;
334 for (int i = 0; i < cur->size; ++i) {
335 HandleChunkElem* elem = chunk_element (cur, i);
336 gpointer* obj_slot = &elem->o;
337 if (*obj_slot != NULL)
338 func (obj_slot, gc_data);
345 HandleChunk *cur = stack->interior;
349 for (int i = 0; i < cur->size; ++i) {
350 HandleChunkElem* elem = chunk_element (cur, i);
351 gpointer* ptr_slot = &elem->o;
352 if (*ptr_slot != NULL)
353 func (ptr_slot, gc_data);
359 mono_stack_mark_record_size (MonoThreadInfo *info, HandleStackMark *stackmark, const char *func_name)
361 HandleStack *handles = (HandleStack *)info->handle_stack;
362 HandleChunk *cur = stackmark->chunk;
363 int size = -stackmark->size; //discard the starting point of the stack
366 if (cur == handles->top)
371 if (size > THIS_IS_AN_OK_NUMBER_OF_HANDLES)
372 g_warning ("%s USED %d handles\n", func_name, size);
376 * Pop the stack until @stackmark and make @value the top value.
378 * @return the new handle for what @value points to
381 mono_stack_mark_pop_value (MonoThreadInfo *info, HandleStackMark *stackmark, MonoRawHandle value)
383 MonoObject *obj = value ? *((MonoObject**)value) : NULL;
384 mono_stack_mark_pop (info, stackmark);
385 #ifndef MONO_HANDLE_TRACK_OWNER
386 return mono_handle_new (obj);
388 return mono_handle_new (obj, "<mono_stack_mark_pop_value>");
392 /* Temporary place for some of the handle enabled wrapper functions*/
395 mono_string_new_handle (MonoDomain *domain, const char *data, MonoError *error)
397 return MONO_HANDLE_NEW (MonoString, mono_string_new_checked (domain, data, error));
401 mono_array_new_handle (MonoDomain *domain, MonoClass *eclass, uintptr_t n, MonoError *error)
403 return MONO_HANDLE_NEW (MonoArray, mono_array_new_checked (domain, eclass, n, error));
407 mono_array_new_full_handle (MonoDomain *domain, MonoClass *array_class, uintptr_t *lengths, intptr_t *lower_bounds, MonoError *error)
409 return MONO_HANDLE_NEW (MonoArray, mono_array_new_full_checked (domain, array_class, lengths, lower_bounds, error));
412 #ifdef ENABLE_CHECKED_BUILD
413 /* Checked build helpers */
415 mono_handle_verify (MonoRawHandle raw_handle)
422 mono_array_handle_length (MonoArrayHandle arr)
424 MONO_REQ_GC_UNSAFE_MODE;
426 return MONO_HANDLE_RAW (arr)->max_length;
430 mono_gchandle_from_handle (MonoObjectHandle handle, mono_bool pinned)
432 /* FIXME: chunk_element_to_chunk_idx does a linear search through the
433 * chunks and we only need it for the assert */
434 MonoThreadInfo *info = mono_thread_info_current ();
435 HandleStack *stack = (HandleStack*) info->handle_stack;
436 HandleChunkElem* elem = handle_to_chunk_element (handle);
438 HandleChunk *chunk = chunk_element_to_chunk_idx (stack, elem, &elem_idx);
439 /* gchandles cannot deal with interior pointers */
440 g_assert (chunk != NULL);
441 return mono_gchandle_new (MONO_HANDLE_RAW (handle), pinned);
445 mono_gchandle_get_target_handle (uint32_t gchandle)
447 return MONO_HANDLE_NEW (MonoObject, mono_gchandle_get_target (gchandle));
451 mono_array_handle_pin_with_size (MonoArrayHandle handle, int size, uintptr_t idx, uint32_t *gchandle)
453 g_assert (gchandle != NULL);
454 *gchandle = mono_gchandle_from_handle (MONO_HANDLE_CAST(MonoObject,handle), TRUE);
455 MonoArray *raw = MONO_HANDLE_RAW (handle);
456 return mono_array_addr_with_size (raw, size, idx);
460 mono_array_handle_memcpy_refs (MonoArrayHandle dest, uintptr_t dest_idx, MonoArrayHandle src, uintptr_t src_idx, uintptr_t len)
462 mono_array_memcpy_refs (MONO_HANDLE_RAW (dest), dest_idx, MONO_HANDLE_RAW (src), src_idx, len);
466 mono_handle_stack_is_empty (HandleStack *stack)
468 return (stack->top == stack->bottom && stack->top->size == 0);