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// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/task/execution_fence.h"
#include <memory>
#include <utility>
#include <vector>
#include "base/check_op.h"
#include "base/feature_list.h"
#include "base/features.h"
#include "base/no_destructor.h"
#include "base/not_fatal_until.h"
#include "base/sequence_checker.h"
#include "base/task/sequence_manager/sequence_manager.h"
#include "base/task/sequence_manager/task_queue.h"
#include "base/task/thread_pool/thread_pool_instance.h"
#include "third_party/abseil-cpp/absl/container/flat_hash_set.h"
namespace base {
using sequence_manager::SequenceManager;
using sequence_manager::TaskQueue;
namespace {
// Global list of SequenceManagers to notify of ScopedBestEffortExecutionFences.
class SequenceManagerRegistry {
public:
SequenceManagerRegistry() = default;
~SequenceManagerRegistry() = default;
SequenceManagerRegistry(const SequenceManagerRegistry&) = delete;
SequenceManagerRegistry& operator=(const SequenceManagerRegistry&) = delete;
static SequenceManagerRegistry& GetInstance() {
static NoDestructor<SequenceManagerRegistry> instance;
return *instance;
}
void AddSequenceManager(SequenceManager* sequence_manager) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
auto [_, inserted] = sequence_managers_.emplace(sequence_manager);
CHECK(inserted, NotFatalUntil::M145);
}
void RemoveSequenceManager(SequenceManager* sequence_manager) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
size_t erased = sequence_managers_.erase(sequence_manager);
CHECK_EQ(erased, 1u, NotFatalUntil::M145);
}
std::vector<std::unique_ptr<TaskQueue::QueueEnabledVoter>>
GetCurrentVoters() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
std::vector<std::unique_ptr<TaskQueue::QueueEnabledVoter>> voters;
for (auto* sequence_manager : sequence_managers_) {
for (TaskQueue* task_queue :
sequence_manager->GetBestEffortTaskQueues()) {
if (task_queue->IsBlockedByScopedExecutionFences()) {
voters.push_back(task_queue->CreateQueueEnabledVoter());
voters.back()->SetVoteToEnable(false);
}
}
}
return voters;
}
private:
SEQUENCE_CHECKER(sequence_checker_);
absl::flat_hash_set<SequenceManager*> sequence_managers_
GUARDED_BY_CONTEXT(sequence_checker_);
};
} // namespace
ScopedThreadPoolExecutionFence::ScopedThreadPoolExecutionFence() {
auto* thread_pool = ThreadPoolInstance::Get();
CHECK(thread_pool, NotFatalUntil::M145);
thread_pool->BeginFence();
}
ScopedThreadPoolExecutionFence::~ScopedThreadPoolExecutionFence() {
auto* thread_pool = ThreadPoolInstance::Get();
CHECK(thread_pool, NotFatalUntil::M145);
thread_pool->EndFence();
}
ScopedBestEffortExecutionFence::ScopedBestEffortExecutionFence() {
if (FeatureList::IsEnabled(
features::kScopedBestEffortExecutionFenceForTaskQueue)) {
task_queue_voters_ =
SequenceManagerRegistry::GetInstance().GetCurrentVoters();
}
auto* thread_pool = ThreadPoolInstance::Get();
CHECK(thread_pool, NotFatalUntil::M145);
thread_pool->BeginBestEffortFence();
}
ScopedBestEffortExecutionFence::~ScopedBestEffortExecutionFence() {
auto* thread_pool = ThreadPoolInstance::Get();
CHECK(thread_pool, NotFatalUntil::M145);
thread_pool->EndBestEffortFence();
}
// static
void ScopedBestEffortExecutionFence::AddSequenceManager(
SequenceManager* sequence_manager) {
SequenceManagerRegistry::GetInstance().AddSequenceManager(sequence_manager);
}
// static
void ScopedBestEffortExecutionFence::RemoveSequenceManager(
SequenceManager* sequence_manager) {
SequenceManagerRegistry::GetInstance().RemoveSequenceManager(
sequence_manager);
}
} // namespace base
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