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sequence_manager_impl.cc
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sequence_manager_impl.cc
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// Copyright 2018 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/sequence_manager/sequence_manager_impl.h"
#include <atomic>
#include <queue>
#include <vector>
#include "base/compiler_specific.h"
#include "base/debug/crash_logging.h"
#include "base/debug/stack_trace.h"
#include "base/functional/bind.h"
#include "base/functional/callback.h"
#include "base/functional/callback_helpers.h"
#include "base/json/json_writer.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/notreached.h"
#include "base/observer_list.h"
#include "base/rand_util.h"
#include "base/ranges/algorithm.h"
#include "base/task/sequence_manager/enqueue_order.h"
#include "base/task/sequence_manager/task_time_observer.h"
#include "base/task/sequence_manager/thread_controller_impl.h"
#include "base/task/sequence_manager/thread_controller_with_message_pump_impl.h"
#include "base/task/sequence_manager/time_domain.h"
#include "base/task/sequence_manager/wake_up_queue.h"
#include "base/task/sequence_manager/work_queue.h"
#include "base/task/sequence_manager/work_queue_sets.h"
#include "base/task/task_features.h"
#include "base/threading/thread_id_name_manager.h"
#include "base/time/default_tick_clock.h"
#include "base/time/tick_clock.h"
#include "base/trace_event/base_tracing.h"
#include "build/build_config.h"
#include "third_party/abseil-cpp/absl/base/attributes.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
#if defined(STARBOARD)
#include <pthread.h>
#include "base/check_op.h"
#include "starboard/thread.h"
#endif
namespace base {
namespace sequence_manager {
namespace {
#if defined(STARBOARD)
ABSL_CONST_INIT pthread_once_t s_once_flag = PTHREAD_ONCE_INIT;
ABSL_CONST_INIT SbThreadLocalKey s_thread_local_key = kSbThreadLocalKeyInvalid;
void InitThreadLocalKey() {
s_thread_local_key = SbThreadCreateLocalKey(NULL);
DCHECK(SbThreadIsValidLocalKey(s_thread_local_key));
}
void EnsureThreadLocalKeyInited() {
pthread_once(&s_once_flag, InitThreadLocalKey);
DCHECK(SbThreadIsValidLocalKey(s_thread_local_key));
}
internal::SequenceManagerImpl* GetThreadLocalSequenceManager() {
return static_cast<internal::SequenceManagerImpl*>(
SbThreadGetLocalValue(s_thread_local_key));
}
#else
ABSL_CONST_INIT thread_local internal::SequenceManagerImpl*
thread_local_sequence_manager = nullptr;
#endif
class TracedBaseValue : public trace_event::ConvertableToTraceFormat {
public:
explicit TracedBaseValue(Value value) : value_(std::move(value)) {}
~TracedBaseValue() override = default;
void AppendAsTraceFormat(std::string* out) const override {
if (!value_.is_none()) {
std::string tmp;
JSONWriter::Write(value_, &tmp);
*out += tmp;
} else {
*out += "{}";
}
}
private:
base::Value value_;
};
} // namespace
std::unique_ptr<SequenceManager> CreateSequenceManagerOnCurrentThread(
SequenceManager::Settings settings) {
return internal::SequenceManagerImpl::CreateOnCurrentThread(
std::move(settings));
}
std::unique_ptr<SequenceManager> CreateSequenceManagerOnCurrentThreadWithPump(
std::unique_ptr<MessagePump> message_pump,
SequenceManager::Settings settings) {
std::unique_ptr<SequenceManager> manager =
internal::SequenceManagerImpl::CreateUnbound(std::move(settings));
manager->BindToMessagePump(std::move(message_pump));
return manager;
}
std::unique_ptr<SequenceManager> CreateUnboundSequenceManager(
SequenceManager::Settings settings) {
return internal::SequenceManagerImpl::CreateUnbound(std::move(settings));
}
namespace internal {
std::unique_ptr<SequenceManagerImpl> CreateUnboundSequenceManagerImpl(
PassKey<base::internal::SequenceManagerThreadDelegate>,
SequenceManager::Settings settings) {
return SequenceManagerImpl::CreateUnbound(std::move(settings));
}
using TimeRecordingPolicy =
base::sequence_manager::TaskQueue::TaskTiming::TimeRecordingPolicy;
namespace {
constexpr TimeDelta kLongTaskTraceEventThreshold = Milliseconds(50);
// Proportion of tasks which will record thread time for metrics.
const double kTaskSamplingRateForRecordingCPUTime = 0.01;
// Proprortion of SequenceManagers which will record thread time for each task,
// enabling advanced metrics.
const double kThreadSamplingRateForRecordingCPUTime = 0.0001;
void ReclaimMemoryFromQueue(internal::TaskQueueImpl* queue, LazyNow* lazy_now) {
queue->ReclaimMemory(lazy_now->Now());
// If the queue was shut down as a side-effect of reclaiming memory, |queue|
// will still be valid but the work queues will have been removed by
// TaskQueueImpl::UnregisterTaskQueue.
if (queue->delayed_work_queue()) {
queue->delayed_work_queue()->RemoveAllCanceledTasksFromFront();
queue->immediate_work_queue()->RemoveAllCanceledTasksFromFront();
}
}
SequenceManager::MetricRecordingSettings InitializeMetricRecordingSettings(
bool randomised_sampling_enabled) {
if (!randomised_sampling_enabled)
return SequenceManager::MetricRecordingSettings(0);
bool records_cpu_time_for_each_task =
base::RandDouble() < kThreadSamplingRateForRecordingCPUTime;
return SequenceManager::MetricRecordingSettings(
records_cpu_time_for_each_task ? 1
: kTaskSamplingRateForRecordingCPUTime);
}
// Writes |address| in hexadecimal ("0x11223344") form starting from |output|
// and moving backwards in memory. Returns a pointer to the first digit of the
// result. Does *not* NUL-terminate the number.
#if !BUILDFLAG(IS_NACL)
char* PrependHexAddress(char* output, const void* address) {
uintptr_t value = reinterpret_cast<uintptr_t>(address);
static const char kHexChars[] = "0123456789ABCDEF";
do {
*output-- = kHexChars[value % 16];
value /= 16;
} while (value);
*output-- = 'x';
*output = '0';
return output;
}
#endif // !BUILDFLAG(IS_NACL)
// Controls whether canceled tasks are removed from the front of the queue when
// deciding when the next wake up should happen.
// Note: An atomic is used here because some tests can initialize two different
// sequence managers on different threads (e.g. by using base::Thread).
std::atomic_bool g_no_wake_ups_for_canceled_tasks{true};
#if BUILDFLAG(IS_WIN)
bool g_explicit_high_resolution_timer_win = false;
#endif // BUILDFLAG(IS_WIN)
} // namespace
// static
SequenceManagerImpl* SequenceManagerImpl::GetCurrent() {
#if defined(STARBOARD)
return GetThreadLocalSequenceManager();
#else
// Workaround false-positive MSAN use-of-uninitialized-value on
// thread_local storage for loaded libraries:
// https://github.com/google/sanitizers/issues/1265
MSAN_UNPOISON(&thread_local_sequence_manager, sizeof(SequenceManagerImpl*));
return thread_local_sequence_manager;
#endif
}
SequenceManagerImpl::SequenceManagerImpl(
std::unique_ptr<internal::ThreadController> controller,
SequenceManager::Settings settings)
: associated_thread_(controller->GetAssociatedThread()),
controller_(std::move(controller)),
settings_(std::move(settings)),
metric_recording_settings_(InitializeMetricRecordingSettings(
settings_.randomised_sampling_enabled)),
add_queue_time_to_tasks_(settings_.add_queue_time_to_tasks),
empty_queues_to_reload_(associated_thread_),
main_thread_only_(this, associated_thread_, settings_, settings_.clock),
clock_(settings_.clock) {
TRACE_EVENT_OBJECT_CREATED_WITH_ID(
TRACE_DISABLED_BY_DEFAULT("sequence_manager"), "SequenceManager", this);
main_thread_only().selector.SetTaskQueueSelectorObserver(this);
main_thread_only().next_time_to_reclaim_memory =
main_thread_clock()->NowTicks() + kReclaimMemoryInterval;
controller_->SetSequencedTaskSource(this);
}
SequenceManagerImpl::~SequenceManagerImpl() {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
TRACE_EVENT_OBJECT_DELETED_WITH_ID(
TRACE_DISABLED_BY_DEFAULT("sequence_manager"), "SequenceManager", this);
#if BUILDFLAG(IS_IOS)
if (settings_.message_loop_type == MessagePumpType::UI &&
associated_thread_->IsBound()) {
controller_->DetachFromMessagePump();
}
#endif
// Make sure no Task is running as given that RunLoop does not support the
// Delegate being destroyed from a Task and
// ThreadControllerWithMessagePumpImpl does not support being destroyed from a
// Task. If we are using a ThreadControllerImpl (i.e. no pump) destruction is
// fine
DCHECK(!controller_->GetBoundMessagePump() ||
main_thread_only().task_execution_stack.empty());
for (internal::TaskQueueImpl* queue : main_thread_only().active_queues) {
main_thread_only().selector.RemoveQueue(queue);
queue->UnregisterTaskQueue();
}
// TODO(altimin): restore default task runner automatically when
// ThreadController is destroyed.
controller_->RestoreDefaultTaskRunner();
main_thread_only().active_queues.clear();
main_thread_only().queues_to_gracefully_shutdown.clear();
main_thread_only().selector.SetTaskQueueSelectorObserver(nullptr);
// In the case of an early startup exits or in some tests a NestingObserver
// may not have been registered.
if (main_thread_only().nesting_observer_registered_)
controller_->RemoveNestingObserver(this);
// Let interested parties have one last shot at accessing this.
for (auto& observer : main_thread_only().destruction_observers)
observer.WillDestroyCurrentMessageLoop();
// OK, now make it so that no one can find us.
if (GetMessagePump()) {
DCHECK_EQ(this, GetCurrent());
#if defined(STARBOARD)
EnsureThreadLocalKeyInited();
SbThreadSetLocalValue(s_thread_local_key, nullptr);
#else
thread_local_sequence_manager = nullptr;
#endif
}
}
SequenceManagerImpl::MainThreadOnly::MainThreadOnly(
SequenceManagerImpl* sequence_manager,
const scoped_refptr<AssociatedThreadId>& associated_thread,
const SequenceManager::Settings& settings,
const base::TickClock* clock)
: selector(associated_thread, settings),
default_clock(clock),
time_domain(nullptr),
wake_up_queue(std::make_unique<DefaultWakeUpQueue>(associated_thread,
sequence_manager)),
non_waking_wake_up_queue(
std::make_unique<NonWakingWakeUpQueue>(associated_thread)) {
if (settings.randomised_sampling_enabled) {
metrics_subsampler = base::MetricsSubSampler();
}
}
SequenceManagerImpl::MainThreadOnly::~MainThreadOnly() = default;
// static
std::unique_ptr<ThreadControllerImpl>
SequenceManagerImpl::CreateThreadControllerImplForCurrentThread(
const TickClock* clock) {
return ThreadControllerImpl::Create(GetCurrent(), clock);
}
// static
std::unique_ptr<SequenceManagerImpl> SequenceManagerImpl::CreateOnCurrentThread(
SequenceManager::Settings settings) {
auto thread_controller =
CreateThreadControllerImplForCurrentThread(settings.clock);
std::unique_ptr<SequenceManagerImpl> manager(new SequenceManagerImpl(
std::move(thread_controller), std::move(settings)));
manager->BindToCurrentThread();
return manager;
}
// static
std::unique_ptr<SequenceManagerImpl> SequenceManagerImpl::CreateUnbound(
SequenceManager::Settings settings) {
auto thread_controller =
ThreadControllerWithMessagePumpImpl::CreateUnbound(settings);
return WrapUnique(new SequenceManagerImpl(std::move(thread_controller),
std::move(settings)));
}
// static
void SequenceManagerImpl::InitializeFeatures() {
base::InitializeTaskLeeway();
ApplyNoWakeUpsForCanceledTasks();
TaskQueueImpl::InitializeFeatures();
ThreadControllerWithMessagePumpImpl::InitializeFeatures();
#if BUILDFLAG(IS_WIN)
g_explicit_high_resolution_timer_win =
FeatureList::IsEnabled(kExplicitHighResolutionTimerWin);
#endif // BUILDFLAG(IS_WIN)
TaskQueueSelector::InitializeFeatures();
}
// static
void SequenceManagerImpl::ApplyNoWakeUpsForCanceledTasks() {
// Since kNoWakeUpsForCanceledTasks is not constexpr (forbidden for Features),
// it cannot be used to initialize |g_no_wake_ups_for_canceled_tasks| at
// compile time. At least DCHECK that its initial value matches the default
// value of the feature here.
DCHECK_EQ(
g_no_wake_ups_for_canceled_tasks.load(std::memory_order_relaxed),
kNoWakeUpsForCanceledTasks.default_state == FEATURE_ENABLED_BY_DEFAULT);
g_no_wake_ups_for_canceled_tasks.store(
FeatureList::IsEnabled(kNoWakeUpsForCanceledTasks),
std::memory_order_relaxed);
}
// static
void SequenceManagerImpl::ResetNoWakeUpsForCanceledTasksForTesting() {
g_no_wake_ups_for_canceled_tasks.store(
kNoWakeUpsForCanceledTasks.default_state == FEATURE_ENABLED_BY_DEFAULT,
std::memory_order_relaxed);
}
void SequenceManagerImpl::BindToMessagePump(std::unique_ptr<MessagePump> pump) {
controller_->BindToCurrentThread(std::move(pump));
CompleteInitializationOnBoundThread();
// On Android attach to the native loop when there is one.
#if BUILDFLAG(IS_ANDROID)
if (settings_.message_loop_type == MessagePumpType::UI ||
settings_.message_loop_type == MessagePumpType::JAVA) {
controller_->AttachToMessagePump();
}
#endif
// On iOS attach to the native loop when there is one.
#if BUILDFLAG(IS_IOS) || defined(STARBOARD)
if (settings_.message_loop_type == MessagePumpType::UI) {
controller_->AttachToMessagePump();
}
#endif
}
void SequenceManagerImpl::BindToCurrentThread() {
associated_thread_->BindToCurrentThread();
CompleteInitializationOnBoundThread();
}
scoped_refptr<SequencedTaskRunner>
SequenceManagerImpl::GetTaskRunnerForCurrentTask() {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
if (main_thread_only().task_execution_stack.empty())
return nullptr;
return main_thread_only()
.task_execution_stack.back()
.pending_task.task_runner;
}
void SequenceManagerImpl::CompleteInitializationOnBoundThread() {
controller_->AddNestingObserver(this);
main_thread_only().nesting_observer_registered_ = true;
if (GetMessagePump()) {
DCHECK(!GetCurrent())
<< "Can't register a second SequenceManagerImpl on the same thread.";
#if defined(STARBOARD)
EnsureThreadLocalKeyInited();
SbThreadSetLocalValue(s_thread_local_key, this);
#else
thread_local_sequence_manager = this;
#endif
}
}
void SequenceManagerImpl::SetTimeDomain(TimeDomain* time_domain) {
DCHECK(!main_thread_only().time_domain);
DCHECK(time_domain);
time_domain->OnAssignedToSequenceManager(this);
controller_->SetTickClock(time_domain);
main_thread_only().time_domain = time_domain;
clock_.store(time_domain, std::memory_order_release);
}
void SequenceManagerImpl::ResetTimeDomain() {
controller_->SetTickClock(main_thread_only().default_clock);
clock_.store(main_thread_only().default_clock.get(),
std::memory_order_release);
main_thread_only().time_domain = nullptr;
}
std::unique_ptr<internal::TaskQueueImpl>
SequenceManagerImpl::CreateTaskQueueImpl(const TaskQueue::Spec& spec) {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
std::unique_ptr<internal::TaskQueueImpl> task_queue =
std::make_unique<internal::TaskQueueImpl>(
this,
spec.non_waking ? main_thread_only().non_waking_wake_up_queue.get()
: main_thread_only().wake_up_queue.get(),
spec);
main_thread_only().active_queues.insert(task_queue.get());
main_thread_only().selector.AddQueue(
task_queue.get(), settings().priority_settings.default_priority());
return task_queue;
}
void SequenceManagerImpl::SetAddQueueTimeToTasks(bool enable) {
base::subtle::NoBarrier_Store(&add_queue_time_to_tasks_, enable ? 1 : 0);
}
bool SequenceManagerImpl::GetAddQueueTimeToTasks() {
return base::subtle::NoBarrier_Load(&add_queue_time_to_tasks_);
}
void SequenceManagerImpl::SetObserver(Observer* observer) {
main_thread_only().observer = observer;
}
void SequenceManagerImpl::ShutdownTaskQueueGracefully(
std::unique_ptr<internal::TaskQueueImpl> task_queue) {
main_thread_only().queues_to_gracefully_shutdown[task_queue.get()] =
std::move(task_queue);
}
void SequenceManagerImpl::UnregisterTaskQueueImpl(
std::unique_ptr<internal::TaskQueueImpl> task_queue) {
TRACE_EVENT1("sequence_manager", "SequenceManagerImpl::UnregisterTaskQueue",
"queue_name", task_queue->GetName());
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
main_thread_only().selector.RemoveQueue(task_queue.get());
// After UnregisterTaskQueue returns no new tasks can be posted.
// It's important to call it first to avoid race condition between removing
// the task queue from various lists here and adding it to the same lists
// when posting a task.
task_queue->UnregisterTaskQueue();
// Add |task_queue| to |main_thread_only().queues_to_delete| so we can prevent
// it from being freed while any of our structures hold hold a raw pointer to
// it.
main_thread_only().active_queues.erase(task_queue.get());
main_thread_only().queues_to_delete[task_queue.get()] = std::move(task_queue);
}
AtomicFlagSet::AtomicFlag
SequenceManagerImpl::GetFlagToRequestReloadForEmptyQueue(
TaskQueueImpl* task_queue) {
return empty_queues_to_reload_.AddFlag(BindRepeating(
&TaskQueueImpl::ReloadEmptyImmediateWorkQueue, Unretained(task_queue)));
}
void SequenceManagerImpl::ReloadEmptyWorkQueues() const {
// There are two cases where a queue needs reloading. First, it might be
// completely empty and we've just posted a task (this method handles that
// case). Secondly if the work queue becomes empty when calling
// WorkQueue::TakeTaskFromWorkQueue (handled there).
//
// Invokes callbacks created by GetFlagToRequestReloadForEmptyQueue above.
empty_queues_to_reload_.RunActiveCallbacks();
}
void SequenceManagerImpl::MoveReadyDelayedTasksToWorkQueues(LazyNow* lazy_now) {
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManagerImpl::MoveReadyDelayedTasksToWorkQueues");
EnqueueOrder delayed_task_group_enqueue_order = GetNextSequenceNumber();
main_thread_only().wake_up_queue->MoveReadyDelayedTasksToWorkQueues(
lazy_now, delayed_task_group_enqueue_order);
main_thread_only()
.non_waking_wake_up_queue->MoveReadyDelayedTasksToWorkQueues(
lazy_now, delayed_task_group_enqueue_order);
}
void SequenceManagerImpl::OnBeginNestedRunLoop() {
main_thread_only().nesting_depth++;
if (main_thread_only().observer)
main_thread_only().observer->OnBeginNestedRunLoop();
}
void SequenceManagerImpl::OnExitNestedRunLoop() {
main_thread_only().nesting_depth--;
DCHECK_GE(main_thread_only().nesting_depth, 0);
if (main_thread_only().nesting_depth == 0) {
// While we were nested some non-nestable tasks may have been deferred. We
// push them back onto the *front* of their original work queues, that's why
// we iterate |non_nestable_task_queue| in LIFO order (we want
// |non_nestable_task.front()| to be the last task pushed at the front of
// |task_queue|).
LazyNow exited_nested_now(main_thread_clock());
while (!main_thread_only().non_nestable_task_queue.empty()) {
internal::TaskQueueImpl::DeferredNonNestableTask& non_nestable_task =
main_thread_only().non_nestable_task_queue.back();
if (!non_nestable_task.task.queue_time.is_null()) {
// Adjust the deferred tasks' queue time to now so that intentionally
// deferred tasks are not unfairly considered as having been stuck in
// the queue for a while. Note: this does not affect task ordering as
// |enqueue_order| is untouched and deferred tasks will still be pushed
// back to the front of the queue.
non_nestable_task.task.queue_time = exited_nested_now.Now();
}
auto* const task_queue = non_nestable_task.task_queue;
task_queue->RequeueDeferredNonNestableTask(std::move(non_nestable_task));
main_thread_only().non_nestable_task_queue.pop_back();
}
}
if (main_thread_only().observer)
main_thread_only().observer->OnExitNestedRunLoop();
}
void SequenceManagerImpl::ScheduleWork() {
controller_->ScheduleWork();
}
void SequenceManagerImpl::SetNextWakeUp(LazyNow* lazy_now,
absl::optional<WakeUp> wake_up) {
auto next_wake_up = AdjustWakeUp(wake_up, lazy_now);
if (next_wake_up && next_wake_up->is_immediate()) {
ScheduleWork();
} else {
controller_->SetNextDelayedDoWork(lazy_now, next_wake_up);
}
}
void SequenceManagerImpl::MaybeEmitTaskDetails(
perfetto::EventContext& ctx,
const SequencedTaskSource::SelectedTask& selected_task) const {
#if BUILDFLAG(ENABLE_BASE_TRACING)
// Other parameters are included only when "scheduler" category is enabled.
const uint8_t* scheduler_category_enabled =
TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED("scheduler");
if (!*scheduler_category_enabled)
return;
auto* event = ctx.event<perfetto::protos::pbzero::ChromeTrackEvent>();
auto* sequence_manager_task = event->set_sequence_manager_task();
sequence_manager_task->set_priority(
settings().priority_settings.TaskPriorityToProto(selected_task.priority));
sequence_manager_task->set_queue_name(selected_task.task_queue_name);
#endif // BUILDFLAG(ENABLE_BASE_TRACING)
}
absl::optional<SequenceManagerImpl::SelectedTask>
SequenceManagerImpl::SelectNextTask(LazyNow& lazy_now,
SelectTaskOption option) {
absl::optional<SelectedTask> selected_task =
SelectNextTaskImpl(lazy_now, option);
return selected_task;
}
#if DCHECK_IS_ON() && !BUILDFLAG(IS_NACL)
void SequenceManagerImpl::LogTaskDebugInfo(
const WorkQueue* selected_work_queue) const {
const Task* task = selected_work_queue->GetFrontTask();
switch (settings_.task_execution_logging) {
case Settings::TaskLogging::kNone:
break;
case Settings::TaskLogging::kEnabled:
LOG(INFO) << "#" << static_cast<uint64_t>(task->enqueue_order()) << " "
<< selected_work_queue->task_queue()->GetName()
<< (task->cross_thread_ ? " Run crossthread " : " Run ")
<< task->posted_from.ToString();
break;
case Settings::TaskLogging::kEnabledWithBacktrace: {
std::array<const void*, PendingTask::kTaskBacktraceLength + 1> task_trace;
task_trace[0] = task->posted_from.program_counter();
ranges::copy(task->task_backtrace, task_trace.begin() + 1);
size_t length = 0;
while (length < task_trace.size() && task_trace[length])
++length;
if (length == 0)
break;
LOG(INFO) << "#" << static_cast<uint64_t>(task->enqueue_order()) << " "
<< selected_work_queue->task_queue()->GetName()
<< (task->cross_thread_ ? " Run crossthread " : " Run ")
<< debug::StackTrace(task_trace.data(), length);
break;
}
case Settings::TaskLogging::kReorderedOnly: {
std::vector<const Task*> skipped_tasks;
main_thread_only().selector.CollectSkippedOverLowerPriorityTasks(
selected_work_queue, &skipped_tasks);
if (skipped_tasks.empty())
break;
LOG(INFO) << "#" << static_cast<uint64_t>(task->enqueue_order()) << " "
<< selected_work_queue->task_queue()->GetName()
<< (task->cross_thread_ ? " Run crossthread " : " Run ")
<< task->posted_from.ToString();
for (const Task* skipped_task : skipped_tasks) {
LOG(INFO) << "# (skipped over) "
<< static_cast<uint64_t>(skipped_task->enqueue_order()) << " "
<< skipped_task->posted_from.ToString();
}
}
}
}
#endif // DCHECK_IS_ON() && !BUILDFLAG(IS_NACL)
absl::optional<SequenceManagerImpl::SelectedTask>
SequenceManagerImpl::SelectNextTaskImpl(LazyNow& lazy_now,
SelectTaskOption option) {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManagerImpl::SelectNextTask");
ReloadEmptyWorkQueues();
MoveReadyDelayedTasksToWorkQueues(&lazy_now);
// If we sampled now, check if it's time to reclaim memory next time we go
// idle.
if (lazy_now.has_value() &&
lazy_now.Now() >= main_thread_only().next_time_to_reclaim_memory) {
main_thread_only().memory_reclaim_scheduled = true;
}
while (true) {
internal::WorkQueue* work_queue =
main_thread_only().selector.SelectWorkQueueToService(option);
TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
TRACE_DISABLED_BY_DEFAULT("sequence_manager.debug"), "SequenceManager",
this,
AsValueWithSelectorResultForTracing(work_queue,
/* force_verbose */ false));
if (!work_queue)
return absl::nullopt;
// If the head task was canceled, remove it and run the selector again.
if (UNLIKELY(work_queue->RemoveAllCanceledTasksFromFront()))
continue;
if (UNLIKELY(work_queue->GetFrontTask()->nestable ==
Nestable::kNonNestable &&
main_thread_only().nesting_depth > 0)) {
// Defer non-nestable work. NOTE these tasks can be arbitrarily delayed so
// the additional delay should not be a problem.
// Note because we don't delete queues while nested, it's perfectly OK to
// store the raw pointer for |queue| here.
internal::TaskQueueImpl::DeferredNonNestableTask deferred_task{
work_queue->TakeTaskFromWorkQueue(), work_queue->task_queue(),
work_queue->queue_type()};
main_thread_only().non_nestable_task_queue.push_back(
std::move(deferred_task));
continue;
}
#if DCHECK_IS_ON() && !BUILDFLAG(IS_NACL)
LogTaskDebugInfo(work_queue);
#endif // DCHECK_IS_ON() && !BUILDFLAG(IS_NACL)
main_thread_only().task_execution_stack.emplace_back(
work_queue->TakeTaskFromWorkQueue(), work_queue->task_queue(),
InitializeTaskTiming(work_queue->task_queue()));
ExecutingTask& executing_task =
*main_thread_only().task_execution_stack.rbegin();
NotifyWillProcessTask(&executing_task, &lazy_now);
// Maybe invalidate the delayed task handle. If already invalidated, then
// don't run this task.
if (!executing_task.pending_task.WillRunTask()) {
executing_task.pending_task.task = DoNothing();
}
return SelectedTask(
executing_task.pending_task,
executing_task.task_queue->task_execution_trace_logger(),
executing_task.priority, executing_task.task_queue_name);
}
}
void SequenceManagerImpl::DidRunTask(LazyNow& lazy_now) {
ExecutingTask& executing_task =
*main_thread_only().task_execution_stack.rbegin();
NotifyDidProcessTask(&executing_task, &lazy_now);
main_thread_only().task_execution_stack.pop_back();
if (main_thread_only().nesting_depth == 0)
CleanUpQueues();
}
void SequenceManagerImpl::RemoveAllCanceledDelayedTasksFromFront(
LazyNow* lazy_now) {
if (!g_no_wake_ups_for_canceled_tasks.load(std::memory_order_relaxed))
return;
main_thread_only().wake_up_queue->RemoveAllCanceledDelayedTasksFromFront(
lazy_now);
main_thread_only()
.non_waking_wake_up_queue->RemoveAllCanceledDelayedTasksFromFront(
lazy_now);
}
absl::optional<WakeUp> SequenceManagerImpl::GetPendingWakeUp(
LazyNow* lazy_now,
SelectTaskOption option) const {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
if (auto priority =
main_thread_only().selector.GetHighestPendingPriority(option)) {
// If the selector has non-empty queues we trivially know there is immediate
// work to be done. However we may want to yield to native work if it is
// more important.
return WakeUp{};
}
// There may be some incoming immediate work which we haven't accounted for.
// NB ReloadEmptyWorkQueues involves a memory barrier, so it's fastest to not
// do this always.
ReloadEmptyWorkQueues();
if (auto priority =
main_thread_only().selector.GetHighestPendingPriority(option)) {
return WakeUp{};
}
// Otherwise we need to find the shortest delay, if any. NB we don't need to
// call MoveReadyDelayedTasksToWorkQueues because it's assumed
// DelayTillNextTask will return TimeDelta>() if the delayed task is due to
// run now.
return AdjustWakeUp(GetNextDelayedWakeUpWithOption(option), lazy_now);
}
absl::optional<WakeUp> SequenceManagerImpl::GetNextDelayedWakeUp() const {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
return main_thread_only().wake_up_queue->GetNextDelayedWakeUp();
}
absl::optional<WakeUp> SequenceManagerImpl::GetNextDelayedWakeUpWithOption(
SelectTaskOption option) const {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
if (option == SelectTaskOption::kSkipDelayedTask)
return absl::nullopt;
return GetNextDelayedWakeUp();
}
absl::optional<WakeUp> SequenceManagerImpl::AdjustWakeUp(
absl::optional<WakeUp> wake_up,
LazyNow* lazy_now) const {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
if (!wake_up)
return absl::nullopt;
// Overdue work needs to be run immediately.
if (lazy_now->Now() >= wake_up->earliest_time())
return WakeUp{};
// If |time_domain| is present, we don't want an actual OS level delayed wake
// up scheduled, so pretend we have no more work. This will result in
// appearing idle and |time_domain| will decide what to do in
// MaybeFastForwardToWakeUp().
if (main_thread_only().time_domain)
return absl::nullopt;
return *wake_up;
}
void SequenceManagerImpl::MaybeAddLeewayToTask(Task& task) const {
if (!main_thread_only().time_domain) {
task.leeway = GetTaskLeewayForCurrentThread();
}
}
// TODO(crbug/1267874): Rename once ExplicitHighResolutionTimerWin experiment is
// shipped.
bool SequenceManagerImpl::HasPendingHighResolutionTasks() {
// Only consider high-res tasks in the |wake_up_queue| (ignore the
// |non_waking_wake_up_queue|).
#if BUILDFLAG(IS_WIN)
if (g_explicit_high_resolution_timer_win) {
absl::optional<WakeUp> wake_up =
main_thread_only().wake_up_queue->GetNextDelayedWakeUp();
if (!wake_up)
return false;
// Under the kExplicitHighResolutionTimerWin experiment, rely on leeway
// being larger than the minimum time of a low resolution timer (16ms). This
// way, we don't need to activate the high resolution timer for precise
// tasks that will run in more than 16ms if there are non precise tasks in
// front of them.
DCHECK_GE(GetDefaultTaskLeeway(),
Milliseconds(Time::kMinLowResolutionThresholdMs));
return wake_up->delay_policy == subtle::DelayPolicy::kPrecise;
}
#endif // BUILDFLAG(IS_WIN)
return main_thread_only().wake_up_queue->has_pending_high_resolution_tasks();
}
bool SequenceManagerImpl::OnSystemIdle() {
bool have_work_to_do = false;
if (main_thread_only().time_domain) {
auto wakeup = main_thread_only().wake_up_queue->GetNextDelayedWakeUp();
have_work_to_do = main_thread_only().time_domain->MaybeFastForwardToWakeUp(
wakeup, controller_->ShouldQuitRunLoopWhenIdle());
}
if (!have_work_to_do) {
MaybeReclaimMemory();
if (main_thread_only().on_next_idle_callback)
std::move(main_thread_only().on_next_idle_callback).Run();
}
return have_work_to_do;
}
void SequenceManagerImpl::WillQueueTask(Task* pending_task) {
controller_->WillQueueTask(pending_task);
}
TaskQueue::TaskTiming SequenceManagerImpl::InitializeTaskTiming(
internal::TaskQueueImpl* task_queue) {
bool records_wall_time =
ShouldRecordTaskTiming(task_queue) == TimeRecordingPolicy::DoRecord;
bool records_thread_time = records_wall_time && ShouldRecordCPUTimeForTask();
return TaskQueue::TaskTiming(records_wall_time, records_thread_time);
}
TimeRecordingPolicy SequenceManagerImpl::ShouldRecordTaskTiming(
const internal::TaskQueueImpl* task_queue) {
if (task_queue->RequiresTaskTiming())
return TimeRecordingPolicy::DoRecord;
if (main_thread_only().nesting_depth == 0 &&
!main_thread_only().task_time_observers.empty()) {
return TimeRecordingPolicy::DoRecord;
}
return TimeRecordingPolicy::DoNotRecord;
}
void SequenceManagerImpl::NotifyWillProcessTask(ExecutingTask* executing_task,
LazyNow* time_before_task) {
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManagerImpl::NotifyWillProcessTaskObservers");
RecordCrashKeys(executing_task->pending_task);
if (executing_task->task_queue->GetQuiescenceMonitored())
main_thread_only().task_was_run_on_quiescence_monitored_queue = true;
TimeRecordingPolicy recording_policy =
ShouldRecordTaskTiming(executing_task->task_queue);
if (recording_policy == TimeRecordingPolicy::DoRecord)
executing_task->task_timing.RecordTaskStart(time_before_task);
if (!executing_task->task_queue->GetShouldNotifyObservers())
return;
const bool was_blocked_or_low_priority =
executing_task->task_queue->WasBlockedOrLowPriority(
executing_task->pending_task.enqueue_order());
{
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManager.WillProcessTaskObservers");
for (auto& observer : main_thread_only().task_observers) {
observer.WillProcessTask(executing_task->pending_task,
was_blocked_or_low_priority);
}
}
{
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManager.QueueNotifyWillProcessTask");
executing_task->task_queue->NotifyWillProcessTask(
executing_task->pending_task, was_blocked_or_low_priority);
}
if (recording_policy != TimeRecordingPolicy::DoRecord)
return;
if (main_thread_only().nesting_depth == 0) {
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManager.WillProcessTaskTimeObservers");
for (auto& observer : main_thread_only().task_time_observers)
observer.WillProcessTask(executing_task->task_timing.start_time());
}
{
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManager.QueueOnTaskStarted");
executing_task->task_queue->OnTaskStarted(executing_task->pending_task,
executing_task->task_timing);
}
}
void SequenceManagerImpl::NotifyDidProcessTask(ExecutingTask* executing_task,
LazyNow* time_after_task) {
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManagerImpl::NotifyDidProcessTaskObservers");
if (!executing_task->task_queue->GetShouldNotifyObservers())
return;
TaskQueue::TaskTiming& task_timing = executing_task->task_timing;
{
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManager.QueueOnTaskCompleted");
if (task_timing.has_wall_time()) {
executing_task->task_queue->OnTaskCompleted(
executing_task->pending_task, &task_timing, time_after_task);
}
}
bool has_valid_start =
task_timing.state() != TaskQueue::TaskTiming::State::NotStarted;
TimeRecordingPolicy recording_policy =
ShouldRecordTaskTiming(executing_task->task_queue);
// Record end time ASAP to avoid bias due to the overhead of observers.
if (recording_policy == TimeRecordingPolicy::DoRecord && has_valid_start) {
task_timing.RecordTaskEnd(time_after_task);
}
if (has_valid_start && task_timing.has_wall_time() &&
main_thread_only().nesting_depth == 0) {
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManager.DidProcessTaskTimeObservers");
for (auto& observer : main_thread_only().task_time_observers) {
observer.DidProcessTask(task_timing.start_time(), task_timing.end_time());
}
}
{
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManager.DidProcessTaskObservers");
for (auto& observer : main_thread_only().task_observers)
observer.DidProcessTask(executing_task->pending_task);
}
{
TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
"SequenceManager.QueueNotifyDidProcessTask");
executing_task->task_queue->NotifyDidProcessTask(
executing_task->pending_task);
}
// TODO(altimin): Move this back to blink.
if (task_timing.has_wall_time() &&
recording_policy == TimeRecordingPolicy::DoRecord &&
task_timing.wall_duration() > kLongTaskTraceEventThreshold &&
main_thread_only().nesting_depth == 0) {
TRACE_EVENT_INSTANT1("blink", "LongTask", TRACE_EVENT_SCOPE_THREAD,
"duration", task_timing.wall_duration().InSecondsF());
}
}
void SequenceManagerImpl::SetWorkBatchSize(int work_batch_size) {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
DCHECK_GE(work_batch_size, 1);
controller_->SetWorkBatchSize(work_batch_size);
}
void SequenceManagerImpl::SetTimerSlack(TimerSlack timer_slack) {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
controller_->SetTimerSlack(timer_slack);
}
void SequenceManagerImpl::AddTaskObserver(TaskObserver* task_observer) {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
main_thread_only().task_observers.AddObserver(task_observer);
}
void SequenceManagerImpl::RemoveTaskObserver(TaskObserver* task_observer) {
DCHECK_CALLED_ON_VALID_THREAD(associated_thread_->thread_checker);
main_thread_only().task_observers.RemoveObserver(task_observer);
}