blob: a923f3f867aba340471b581f0a751c81df7dc649 [file] [log] [blame]
// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <memory>
#include <queue>
#include "include/libplatform/libplatform.h"
#include "include/v8-platform.h"
#include "src/base/platform/condition-variable.h"
#include "src/base/platform/mutex.h"
namespace v8 {
namespace platform {
class V8_PLATFORM_EXPORT DefaultForegroundTaskRunner
: public NON_EXPORTED_BASE(TaskRunner) {
using TimeFunction = double (*)();
class RunTaskScope {
explicit RunTaskScope(
std::shared_ptr<DefaultForegroundTaskRunner> task_runner);
RunTaskScope(const RunTaskScope&) = delete;
RunTaskScope& operator=(const RunTaskScope&) = delete;
std::shared_ptr<DefaultForegroundTaskRunner> task_runner_;
DefaultForegroundTaskRunner(IdleTaskSupport idle_task_support,
TimeFunction time_function);
void Terminate();
std::unique_ptr<Task> PopTaskFromQueue(MessageLoopBehavior wait_for_work);
std::unique_ptr<IdleTask> PopTaskFromIdleQueue();
void WaitForTaskLocked(const base::MutexGuard&);
double MonotonicallyIncreasingTime();
// v8::TaskRunner implementation.
void PostTask(std::unique_ptr<Task> task) override;
void PostDelayedTask(std::unique_ptr<Task> task,
double delay_in_seconds) override;
void PostIdleTask(std::unique_ptr<IdleTask> task) override;
bool IdleTasksEnabled() override;
void PostNonNestableTask(std::unique_ptr<Task> task) override;
bool NonNestableTasksEnabled() const override;
enum Nestability { kNestable, kNonNestable };
// The same as PostTask or PostNonNestableTask, but the lock is already held
// by the caller. The {guard} parameter should make sure that the caller is
// holding the lock.
void PostTaskLocked(std::unique_ptr<Task> task, Nestability nestability,
const base::MutexGuard&);
// A caller of this function has to hold {lock_}. The {guard} parameter should
// make sure that the caller is holding the lock.
std::unique_ptr<Task> PopTaskFromDelayedQueueLocked(const base::MutexGuard&);
// A non-nestable task is poppable only if the task runner is not nested,
// i.e. if a task is not being run from within a task. A nestable task is
// always poppable.
bool HasPoppableTaskInQueue() const;
bool terminated_ = false;
base::Mutex lock_;
base::ConditionVariable event_loop_control_;
int nesting_depth_ = 0;
using TaskQueueEntry = std::pair<Nestability, std::unique_ptr<Task>>;
std::deque<TaskQueueEntry> task_queue_;
IdleTaskSupport idle_task_support_;
std::queue<std::unique_ptr<IdleTask>> idle_task_queue_;
// Some helper constructs for the {delayed_task_queue_}.
using DelayedEntry = std::pair<double, std::unique_ptr<Task>>;
// Define a comparison operator for the delayed_task_queue_ to make sure
// that the unique_ptr in the DelayedEntry is not accessed in the priority
// queue. This is necessary because we have to reset the unique_ptr when we
// remove a DelayedEntry from the priority queue.
struct DelayedEntryCompare {
bool operator()(const DelayedEntry& left, const DelayedEntry& right) const {
return left.first > right.first;
std::priority_queue<DelayedEntry, std::vector<DelayedEntry>,
TimeFunction time_function_;
} // namespace platform
} // namespace v8