monitor_pool.cc revision 8cf9cb386cd9286d67e879f1ee501ec00d72a4e1 
1/*
2 * Copyright (C) 2014 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#include "monitor_pool.h"
18
19#include "base/logging.h"
20#include "base/mutex-inl.h"
21#include "monitor.h"
22#include "thread-current-inl.h"
23
24namespace art {
25
26namespace mirror {
27  class Object;
28}  // namespace mirror
29
30MonitorPool::MonitorPool()
31    : current_chunk_list_index_(0), num_chunks_(0), current_chunk_list_capacity_(0),
32    first_free_(nullptr) {
33  for (size_t i = 0; i < kMaxChunkLists; ++i) {
34    monitor_chunks_[i] = nullptr;  // Not absolutely required, but ...
35  }
36  AllocateChunk();  // Get our first chunk.
37}
38
39// Assumes locks are held appropriately when necessary.
40// We do not need a lock in the constructor, but we need one when in CreateMonitorInPool.
41void MonitorPool::AllocateChunk() {
42  DCHECK(first_free_ == nullptr);
43
44  // Do we need to allocate another chunk list?
45  if (num_chunks_ == current_chunk_list_capacity_) {
46    if (current_chunk_list_capacity_ != 0U) {
47      ++current_chunk_list_index_;
48      CHECK_LT(current_chunk_list_index_, kMaxChunkLists) << "Out of space for inflated monitors";
49      VLOG(monitor) << "Expanding to capacity "
50          << 2 * ChunkListCapacity(current_chunk_list_index_) - kInitialChunkStorage;
51    }  // else we're initializing
52    current_chunk_list_capacity_ = ChunkListCapacity(current_chunk_list_index_);
53    uintptr_t* new_list = new uintptr_t[current_chunk_list_capacity_]();
54    DCHECK(monitor_chunks_[current_chunk_list_index_] == nullptr);
55    monitor_chunks_[current_chunk_list_index_] = new_list;
56    num_chunks_ = 0;
57  }
58
59  // Allocate the chunk.
60  void* chunk = allocator_.allocate(kChunkSize);
61  // Check we allocated memory.
62  CHECK_NE(reinterpret_cast<uintptr_t>(nullptr), reinterpret_cast<uintptr_t>(chunk));
63  // Check it is aligned as we need it.
64  CHECK_EQ(0U, reinterpret_cast<uintptr_t>(chunk) % kMonitorAlignment);
65
66  // Add the chunk.
67  monitor_chunks_[current_chunk_list_index_][num_chunks_] = reinterpret_cast<uintptr_t>(chunk);
68  num_chunks_++;
69
70  // Set up the free list
71  Monitor* last = reinterpret_cast<Monitor*>(reinterpret_cast<uintptr_t>(chunk) +
72                                             (kChunkCapacity - 1) * kAlignedMonitorSize);
73  last->next_free_ = nullptr;
74  // Eagerly compute id.
75  last->monitor_id_ = OffsetToMonitorId(current_chunk_list_index_* (kMaxListSize * kChunkSize)
76      + (num_chunks_ - 1) * kChunkSize + (kChunkCapacity - 1) * kAlignedMonitorSize);
77  for (size_t i = 0; i < kChunkCapacity - 1; ++i) {
78    Monitor* before = reinterpret_cast<Monitor*>(reinterpret_cast<uintptr_t>(last) -
79                                                 kAlignedMonitorSize);
80    before->next_free_ = last;
81    // Derive monitor_id from last.
82    before->monitor_id_ = OffsetToMonitorId(MonitorIdToOffset(last->monitor_id_) -
83                                            kAlignedMonitorSize);
84
85    last = before;
86  }
87  DCHECK(last == reinterpret_cast<Monitor*>(chunk));
88  first_free_ = last;
89}
90
91void MonitorPool::FreeInternal() {
92  // This is on shutdown with NO_THREAD_SAFETY_ANALYSIS, can't/don't need to lock.
93  DCHECK_NE(current_chunk_list_capacity_, 0UL);
94  for (size_t i = 0; i <= current_chunk_list_index_; ++i) {
95    DCHECK_NE(monitor_chunks_[i], static_cast<uintptr_t*>(nullptr));
96    for (size_t j = 0; j < ChunkListCapacity(i); ++j) {
97      if (i < current_chunk_list_index_ || j < num_chunks_) {
98        DCHECK_NE(monitor_chunks_[i][j], 0U);
99        allocator_.deallocate(reinterpret_cast<uint8_t*>(monitor_chunks_[i][j]), kChunkSize);
100      } else {
101        DCHECK_EQ(monitor_chunks_[i][j], 0U);
102      }
103    }
104    delete[] monitor_chunks_[i];
105  }
106}
107
108Monitor* MonitorPool::CreateMonitorInPool(Thread* self, Thread* owner, mirror::Object* obj,
109                                          int32_t hash_code)
110    REQUIRES_SHARED(Locks::mutator_lock_) {
111  // We are gonna allocate, so acquire the writer lock.
112  MutexLock mu(self, *Locks::allocated_monitor_ids_lock_);
113
114  // Enough space, or need to resize?
115  if (first_free_ == nullptr) {
116    VLOG(monitor) << "Allocating a new chunk.";
117    AllocateChunk();
118  }
119
120  Monitor* mon_uninitialized = first_free_;
121  first_free_ = first_free_->next_free_;
122
123  // Pull out the id which was preinitialized.
124  MonitorId id = mon_uninitialized->monitor_id_;
125
126  // Initialize it.
127  Monitor* monitor = new(mon_uninitialized) Monitor(self, owner, obj, hash_code, id);
128
129  return monitor;
130}
131
132void MonitorPool::ReleaseMonitorToPool(Thread* self, Monitor* monitor) {
133  // Might be racy with allocation, so acquire lock.
134  MutexLock mu(self, *Locks::allocated_monitor_ids_lock_);
135
136  // Keep the monitor id. Don't trust it's not cleared.
137  MonitorId id = monitor->monitor_id_;
138
139  // Call the destructor.
140  // TODO: Exception safety?
141  monitor->~Monitor();
142
143  // Add to the head of the free list.
144  monitor->next_free_ = first_free_;
145  first_free_ = monitor;
146
147  // Rewrite monitor id.
148  monitor->monitor_id_ = id;
149}
150
151void MonitorPool::ReleaseMonitorsToPool(Thread* self, MonitorList::Monitors* monitors) {
152  for (Monitor* mon : *monitors) {
153    ReleaseMonitorToPool(self, mon);
154  }
155}
156
157}  // namespace art
158