2 * handle.c: Handle to object in native code
5 * - Ludovic Henry <ludovic@xamarin.com>
6 * - Aleksey Klieger <aleksey.klieger@xamarin.com>
7 * - Rodrigo Kumpera <kumpera@xamarin.com>
9 * Copyright 2016 Dot net foundation.
10 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
16 #include <mono/metadata/handle.h>
17 #include <mono/metadata/object-internals.h>
18 #include <mono/metadata/gc-internals.h>
19 #include <mono/utils/atomic.h>
20 #include <mono/utils/mono-lazy-init.h>
21 #include <mono/utils/mono-threads.h>
22 /* TODO (missing pieces)
27 mix/max/avg size of stack marks
30 Actually do something in mono_handle_verify
32 Shrink the handles stack in mono_handle_stack_scan
33 Properly report it to the profiler.
34 Add a boehm implementation
36 TODO (things to explore):
38 There's no convenient way to wrap the object allocation function.
40 MonoCultureInfoHandle culture = MONO_HANDLE_NEW (MonoCultureInfo, mono_object_new_checked (domain, klass, &error));
42 Maybe what we need is a round of cleanup around all exposed types in the runtime to unify all helpers under the same hoof.
43 Combine: MonoDefaults, GENERATE_GET_CLASS_WITH_CACHE, TYPED_HANDLE_DECL and friends.
44 This would solve the age old issue of making it clear which types are optional and tell that to the linker.
45 We could then generate neat type safe wrappers.
51 * If we are running with cooperative GC, all the handle stack
52 * manipulation will complete before a GC thread scans the handle
53 * stack. If we are using async suspend, however, a thread may be
54 * trying to allocate a new handle, or unwind the handle stack when
55 * the GC stops the world.
57 * In particular, we need to ensure that if the mutator thread is
58 * suspended while manipulating the handle stack, the stack is in a
59 * good enough state to be scanned. In particular, the size of each
60 * chunk should be updated before an object is written into the
61 * handle, and chunks to be scanned (between bottom and top) should
64 * Note that the handle stack is scanned PRECISELY (see
65 * sgen_client_scan_thread_data ()). That means there should not be
66 * stale objects scanned. So when we manipulate the size of a chunk,
67 * wemust ensure that the newly scannable slot is either null or
68 * points to a valid value.
71 const MonoObjectHandle mono_null_value_handle = NULL;
73 #define THIS_IS_AN_OK_NUMBER_OF_HANDLES 100
75 /* Actual handles implementation */
77 mono_handle_new (MonoObject *object)
79 MonoThreadInfo *info = mono_thread_info_current ();
80 HandleStack *handles = (HandleStack *)info->handle_stack;
81 HandleChunk *top = handles->top;
84 if (G_LIKELY (top->size < OBJECTS_PER_HANDLES_CHUNK)) {
86 /* can be interrupted anywhere here, so:
87 * 1. make sure the new slot is null
88 * 2. make the new slot scannable (increment size)
89 * 3. put a valid object in there
91 * (have to do 1 then 3 so that if we're interrupted
92 * between 1 and 2, the object is still live)
94 top->objects [idx] = NULL;
95 mono_memory_write_barrier ();
97 mono_memory_write_barrier ();
98 MonoObject **h = &top->objects [idx];
102 if (G_LIKELY (top->next)) {
104 /* make sure size == 0 is visible to a GC thread before it sees the new top */
105 mono_memory_write_barrier ();
110 HandleChunk *new_chunk = g_new (HandleChunk, 1);
112 new_chunk->prev = top;
113 new_chunk->next = NULL;
114 /* make sure size == 0 before new chunk is visible */
115 mono_memory_write_barrier ();
116 top->next = new_chunk;
117 handles->top = new_chunk;
124 mono_handle_stack_alloc (void)
126 HandleStack *stack = g_new (HandleStack, 1);
127 HandleChunk *chunk = g_new (HandleChunk, 1);
130 chunk->prev = chunk->next = NULL;
131 mono_memory_write_barrier ();
132 stack->top = stack->bottom = chunk;
137 mono_handle_stack_free (HandleStack *stack)
141 HandleChunk *c = stack->bottom;
142 stack->top = stack->bottom = NULL;
143 mono_memory_write_barrier ();
145 HandleChunk *next = c->next;
154 mono_handle_stack_scan (HandleStack *stack, GcScanFunc func, gpointer gc_data)
156 /* if we're running, we know the world is stopped.
158 HandleChunk *cur = stack->bottom;
159 HandleChunk *last = stack->top;
166 for (i = 0; i < cur->size; ++i) {
167 if (cur->objects [i] != NULL)
168 func ((gpointer*)&cur->objects [i], gc_data);
177 mono_stack_mark_record_size (MonoThreadInfo *info, HandleStackMark *stackmark, const char *func_name)
179 HandleStack *handles = (HandleStack *)info->handle_stack;
180 HandleChunk *cur = stackmark->chunk;
181 int size = -stackmark->size; //discard the starting point of the stack
184 if (cur == handles->top)
189 if (size > THIS_IS_AN_OK_NUMBER_OF_HANDLES)
190 g_warning ("%s USED %d handles\n", func_name, size);
194 * Pop the stack until @stackmark and make @value the top value.
196 * @return the new handle for what @value points to
199 mono_stack_mark_pop_value (MonoThreadInfo *info, HandleStackMark *stackmark, MonoRawHandle value)
204 /* Temporary place for some of the handle enabled wrapper functions*/
207 mono_string_new_handle (MonoDomain *domain, const char *data, MonoError *error)
209 return MONO_HANDLE_NEW (MonoString, mono_string_new_checked (domain, data, error));
213 mono_array_new_handle (MonoDomain *domain, MonoClass *eclass, uintptr_t n, MonoError *error)
215 return MONO_HANDLE_NEW (MonoArray, mono_array_new_checked (domain, eclass, n, error));
218 #ifdef ENABLE_CHECKED_BUILD
219 /* Checked build helpers */
221 mono_handle_verify (MonoRawHandle raw_handle)
228 mono_array_handle_length (MonoArrayHandle arr)
230 MONO_REQ_GC_UNSAFE_MODE;
232 return MONO_HANDLE_RAW (arr)->max_length;
236 mono_gchandle_from_handle (MonoObjectHandle handle, mono_bool pinned)
238 return mono_gchandle_new (MONO_HANDLE_RAW(handle), pinned);
242 mono_gchandle_get_target_handle (uint32_t gchandle)
244 return MONO_HANDLE_NEW (MonoObject, mono_gchandle_get_target);
248 mono_array_handle_pin_with_size (MonoArrayHandle handle, int size, uintptr_t idx, uint32_t *gchandle)
250 g_assert (gchandle != NULL);
251 *gchandle = mono_gchandle_from_handle (MONO_HANDLE_CAST(MonoObject,handle), TRUE);
252 MonoArray *raw = MONO_HANDLE_RAW (handle);
253 return mono_array_addr_with_size (raw, size, idx);
257 mono_array_handle_memcpy_refs (MonoArrayHandle dest, uintptr_t dest_idx, MonoArrayHandle src, uintptr_t src_idx, uintptr_t len)
259 mono_array_memcpy_refs (MONO_HANDLE_RAW (dest), dest_idx, MONO_HANDLE_RAW (src), src_idx, len);