1 /*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #ifndef ART_RUNTIME_GC_SPACE_BUMP_POINTER_SPACE_WALK_INL_H_
18 #define ART_RUNTIME_GC_SPACE_BUMP_POINTER_SPACE_WALK_INL_H_
19
20 #include "bump_pointer_space.h"
21
22 #include "base/bit_utils.h"
23 #include "mirror/object-inl.h"
24 #include "thread-current-inl.h"
25
26 namespace art {
27 namespace gc {
28 namespace space {
29
30 template <typename Visitor>
Walk(Visitor && visitor)31 inline void BumpPointerSpace::Walk(Visitor&& visitor) {
32 uint8_t* pos = Begin();
33 uint8_t* end = End();
34 uint8_t* main_end = pos;
35 // Internal indirection w/ NO_THREAD_SAFETY_ANALYSIS. Optimally, we'd like to have an annotation
36 // like
37 // REQUIRES_AS(visitor.operator(mirror::Object*))
38 // on Walk to expose the interprocedural nature of locks here without having to duplicate the
39 // function.
40 //
41 // NO_THREAD_SAFETY_ANALYSIS is a workaround. The problem with the workaround of course is that
42 // it doesn't complain at the callsite. However, that is strictly not worse than the
43 // ObjectCallback version it replaces.
44 auto no_thread_safety_analysis_visit = [&](mirror::Object* obj) NO_THREAD_SAFETY_ANALYSIS {
45 visitor(obj);
46 };
47
48 {
49 MutexLock mu(Thread::Current(), block_lock_);
50 // If we have 0 blocks then we need to update the main header since we have bump pointer style
51 // allocation into an unbounded region (actually bounded by Capacity()).
52 if (num_blocks_ == 0) {
53 UpdateMainBlock();
54 }
55 main_end = Begin() + main_block_size_;
56 if (num_blocks_ == 0) {
57 // We don't have any other blocks, this means someone else may be allocating into the main
58 // block. In this case, we don't want to try and visit the other blocks after the main block
59 // since these could actually be part of the main block.
60 end = main_end;
61 }
62 }
63 // Walk all of the objects in the main block first.
64 while (pos < main_end) {
65 mirror::Object* obj = reinterpret_cast<mirror::Object*>(pos);
66 // No read barrier because obj may not be a valid object.
67 if (obj->GetClass<kDefaultVerifyFlags, kWithoutReadBarrier>() == nullptr) {
68 // There is a race condition where a thread has just allocated an object but not set the
69 // class. We can't know the size of this object, so we don't visit it and exit the function
70 // since there is guaranteed to be not other blocks.
71 return;
72 } else {
73 no_thread_safety_analysis_visit(obj);
74 pos = reinterpret_cast<uint8_t*>(GetNextObject(obj));
75 }
76 }
77 // Walk the other blocks (currently only TLABs).
78 while (pos < end) {
79 BlockHeader* header = reinterpret_cast<BlockHeader*>(pos);
80 size_t block_size = header->size_;
81 pos += sizeof(BlockHeader); // Skip the header so that we know where the objects
82 mirror::Object* obj = reinterpret_cast<mirror::Object*>(pos);
83 const mirror::Object* end_obj = reinterpret_cast<const mirror::Object*>(pos + block_size);
84 CHECK_LE(reinterpret_cast<const uint8_t*>(end_obj), End());
85 // We don't know how many objects are allocated in the current block. When we hit a null class
86 // assume its the end. TODO: Have a thread update the header when it flushes the block?
87 // No read barrier because obj may not be a valid object.
88 while (obj < end_obj && obj->GetClass<kDefaultVerifyFlags, kWithoutReadBarrier>() != nullptr) {
89 no_thread_safety_analysis_visit(obj);
90 obj = GetNextObject(obj);
91 }
92 pos += block_size;
93 }
94 }
95
96 } // namespace space
97 } // namespace gc
98 } // namespace art
99
100 #endif // ART_RUNTIME_GC_SPACE_BUMP_POINTER_SPACE_WALK_INL_H_
101