141 lines
4.6 KiB
C++
141 lines
4.6 KiB
C++
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "monitor_pool.h"
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#include "base/logging.h"
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#include "base/mutex-inl.h"
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#include "thread-inl.h"
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#include "monitor.h"
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namespace art {
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namespace mirror {
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class Object;
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} // namespace mirror
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MonitorPool::MonitorPool()
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: num_chunks_(0), capacity_(0), first_free_(nullptr) {
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AllocateChunk(); // Get our first chunk.
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}
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// Assumes locks are held appropriately when necessary.
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// We do not need a lock in the constructor, but we need one when in CreateMonitorInPool.
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void MonitorPool::AllocateChunk() {
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DCHECK(first_free_ == nullptr);
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// Do we need to resize?
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if (num_chunks_ == capacity_) {
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if (capacity_ == 0U) {
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// Initialization.
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capacity_ = kInitialChunkStorage;
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uintptr_t* new_backing = new uintptr_t[capacity_];
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monitor_chunks_.StoreRelaxed(new_backing);
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} else {
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size_t new_capacity = 2 * capacity_;
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uintptr_t* new_backing = new uintptr_t[new_capacity];
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uintptr_t* old_backing = monitor_chunks_.LoadRelaxed();
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memcpy(new_backing, old_backing, sizeof(uintptr_t) * capacity_);
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monitor_chunks_.StoreRelaxed(new_backing);
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capacity_ = new_capacity;
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old_chunk_arrays_.push_back(old_backing);
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VLOG(monitor) << "Resizing to capacity " << capacity_;
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}
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}
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// Allocate the chunk.
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void* chunk = allocator_.allocate(kChunkSize);
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// Check we allocated memory.
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CHECK_NE(reinterpret_cast<uintptr_t>(nullptr), reinterpret_cast<uintptr_t>(chunk));
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// Check it is aligned as we need it.
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CHECK_EQ(0U, reinterpret_cast<uintptr_t>(chunk) % kMonitorAlignment);
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// Add the chunk.
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*(monitor_chunks_.LoadRelaxed() + num_chunks_) = reinterpret_cast<uintptr_t>(chunk);
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num_chunks_++;
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// Set up the free list
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Monitor* last = reinterpret_cast<Monitor*>(reinterpret_cast<uintptr_t>(chunk) +
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(kChunkCapacity - 1) * kAlignedMonitorSize);
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last->next_free_ = nullptr;
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// Eagerly compute id.
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last->monitor_id_ = OffsetToMonitorId((num_chunks_ - 1) * kChunkSize +
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(kChunkCapacity - 1) * kAlignedMonitorSize);
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for (size_t i = 0; i < kChunkCapacity - 1; ++i) {
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Monitor* before = reinterpret_cast<Monitor*>(reinterpret_cast<uintptr_t>(last) -
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kAlignedMonitorSize);
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before->next_free_ = last;
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// Derive monitor_id from last.
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before->monitor_id_ = OffsetToMonitorId(MonitorIdToOffset(last->monitor_id_) -
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kAlignedMonitorSize);
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last = before;
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}
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DCHECK(last == reinterpret_cast<Monitor*>(chunk));
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first_free_ = last;
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}
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Monitor* MonitorPool::CreateMonitorInPool(Thread* self, Thread* owner, mirror::Object* obj,
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int32_t hash_code)
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SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
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// We are gonna allocate, so acquire the writer lock.
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MutexLock mu(self, *Locks::allocated_monitor_ids_lock_);
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// Enough space, or need to resize?
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if (first_free_ == nullptr) {
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VLOG(monitor) << "Allocating a new chunk.";
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AllocateChunk();
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}
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Monitor* mon_uninitialized = first_free_;
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first_free_ = first_free_->next_free_;
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// Pull out the id which was preinitialized.
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MonitorId id = mon_uninitialized->monitor_id_;
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// Initialize it.
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Monitor* monitor = new(mon_uninitialized) Monitor(self, owner, obj, hash_code, id);
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return monitor;
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}
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void MonitorPool::ReleaseMonitorToPool(Thread* self, Monitor* monitor) {
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// Might be racy with allocation, so acquire lock.
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MutexLock mu(self, *Locks::allocated_monitor_ids_lock_);
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// Keep the monitor id. Don't trust it's not cleared.
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MonitorId id = monitor->monitor_id_;
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// Call the destructor.
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// TODO: Exception safety?
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monitor->~Monitor();
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// Add to the head of the free list.
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monitor->next_free_ = first_free_;
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first_free_ = monitor;
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// Rewrite monitor id.
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monitor->monitor_id_ = id;
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}
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void MonitorPool::ReleaseMonitorsToPool(Thread* self, MonitorList::Monitors* monitors) {
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for (Monitor* mon : *monitors) {
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ReleaseMonitorToPool(self, mon);
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}
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}
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} // namespace art
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