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