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      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 "thread-inl.h"
     22 #include "monitor.h"
     23 
     24 namespace art {
     25 
     26 namespace mirror {
     27   class Object;
     28 }  // namespace mirror
     29 
     30 MonitorPool::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.
     41 void 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 
     91 void 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 
    108 Monitor* 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 
    132 void 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 
    151 void MonitorPool::ReleaseMonitorsToPool(Thread* self, MonitorList::Monitors* monitors) {
    152   for (Monitor* mon : *monitors) {
    153     ReleaseMonitorToPool(self, mon);
    154   }
    155 }
    156 
    157 }  // namespace art
    158