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// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/reporting/resources/resource_manager.h"
#include <atomic>
#include <cstdint>
#include <optional>
#include <utility>
#include "base/logging.h"
#include "base/memory/ref_counted.h"
#include "base/memory/scoped_refptr.h"
#include "base/sequence_checker.h"
#include "base/task/bind_post_task.h"
#include "base/task/sequenced_task_runner.h"
#include "base/task/task_traits.h"
#include "base/task/thread_pool.h"
namespace reporting {
ResourceManager::ResourceManager(uint64_t total_size)
: total_(total_size),
sequenced_task_runner_(base::ThreadPool::CreateSequencedTaskRunner(
{base::TaskPriority::BEST_EFFORT})) {
DETACH_FROM_SEQUENCE(sequence_checker_);
}
ResourceManager::~ResourceManager() = default;
bool ResourceManager::Reserve(uint64_t size) {
uint64_t old_used = used_.fetch_add(size);
if (old_used + size > total_) {
used_.fetch_sub(size);
return false;
}
return true;
}
void ResourceManager::Discard(uint64_t size) {
CHECK_LE(size, used_.load());
used_.fetch_sub(size);
sequenced_task_runner_->PostTask(
FROM_HERE, base::BindOnce(&ResourceManager::FlushCallbacks,
base::WrapRefCounted(this)));
}
uint64_t ResourceManager::GetTotal() const {
return total_;
}
uint64_t ResourceManager::GetUsed() const {
return used_.load();
}
void ResourceManager::Test_SetTotal(uint64_t test_total) {
total_ = test_total;
}
void ResourceManager::RegisterCallback(uint64_t size, base::OnceClosure cb) {
sequenced_task_runner_->PostTask(
FROM_HERE, base::BindOnce(
[](scoped_refptr<ResourceManager> self, uint64_t size,
base::OnceClosure cb) {
DCHECK_CALLED_ON_VALID_SEQUENCE(self->sequence_checker_);
self->resource_callbacks_.emplace(size, std::move(cb));
// Attempt to apply remaining callbacks
// (this is especially important if the new callback is
// registered with no allocations to be released - we
// don't want the callback to wait indefinitely in this
// case).
self->FlushCallbacks();
},
base::WrapRefCounted(this), size,
base::BindPostTaskToCurrentDefault(std::move(cb))));
}
void ResourceManager::FlushCallbacks() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
int64_t remained = GetTotal() - GetUsed(); // No synchronization whatsoever.
while (remained > 0 && !resource_callbacks_.empty()) {
auto& cb_pair = resource_callbacks_.front();
if (cb_pair.first > static_cast<uint64_t>(remained)) {
break;
}
remained -= cb_pair.first;
std::move(cb_pair.second).Run();
resource_callbacks_.pop();
}
}
ScopedReservation::ScopedReservation() noexcept = default;
ScopedReservation::ScopedReservation(
uint64_t size,
scoped_refptr<ResourceManager> resource_manager) noexcept
: resource_manager_(resource_manager) {
if (size == 0uL || !resource_manager->Reserve(size)) {
return;
}
size_ = size;
}
ScopedReservation::ScopedReservation(
uint64_t size,
const ScopedReservation& other_reservation) noexcept
: resource_manager_(other_reservation.resource_manager_) {
if (size == 0uL || !resource_manager_.get() ||
!resource_manager_->Reserve(size)) {
return;
}
size_ = size;
}
ScopedReservation::ScopedReservation(ScopedReservation&& other) noexcept
: resource_manager_(other.resource_manager_),
size_(std::exchange(other.size_, std::nullopt)) {}
bool ScopedReservation::reserved() const {
return size_.has_value();
}
bool ScopedReservation::Reduce(uint64_t new_size) {
if (!reserved()) {
return false;
}
if (new_size < 0 || size_.value() < new_size) {
return false;
}
resource_manager_->Discard(size_.value() - new_size);
if (new_size > 0) {
size_ = new_size;
} else {
size_ = std::nullopt;
}
return true;
}
void ScopedReservation::HandOver(ScopedReservation& other) {
if (resource_manager_.get()) {
CHECK_EQ(resource_manager_.get(), other.resource_manager_.get())
<< "Reservations are not related";
} else {
CHECK(!reserved()) << "Unattached reservation may not have size";
resource_manager_ = other.resource_manager_;
}
if (!other.reserved()) {
return; // Nothing changes.
}
const uint64_t old_size = (reserved() ? size_.value() : 0uL);
size_ = old_size + std::exchange(other.size_, std::nullopt).value();
}
ScopedReservation::~ScopedReservation() {
if (reserved()) {
resource_manager_->Discard(size_.value());
}
}
} // namespace reporting
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