gecko-dev/xpcom/threads/TaskController.cpp

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C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "TaskController.h"
#include "nsIIdleRunnable.h"
#include "nsIRunnable.h"
#include "nsThreadUtils.h"
#include <algorithm>
#include <initializer_list>
#include "mozilla/AbstractEventQueue.h"
#include "mozilla/BackgroundHangMonitor.h"
#include "mozilla/InputTaskManager.h"
#include "mozilla/StaticMutex.h"
#include "mozilla/SchedulerGroup.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/Unused.h"
#include "nsIThreadInternal.h"
#include "nsQueryObject.h"
#include "nsThread.h"
namespace mozilla {
std::unique_ptr<TaskController> TaskController::sSingleton;
uint64_t Task::sCurrentTaskSeqNo = 0;
bool TaskManager::
UpdateCachesForCurrentIterationAndReportPriorityModifierChanged(
const MutexAutoLock& aProofOfLock, IterationType aIterationType) {
mCurrentSuspended = IsSuspended(aProofOfLock);
if (aIterationType == IterationType::EVENT_LOOP_TURN) {
int32_t oldModifier = mCurrentPriorityModifier;
mCurrentPriorityModifier =
GetPriorityModifierForEventLoopTurn(aProofOfLock);
if (mCurrentPriorityModifier != oldModifier) {
return true;
}
}
return false;
}
Task* Task::GetHighestPriorityDependency() {
Task* currentTask = this;
while (!currentTask->mDependencies.empty()) {
auto iter = currentTask->mDependencies.begin();
while (iter != currentTask->mDependencies.end()) {
if ((*iter)->mCompleted) {
auto oldIter = iter;
iter++;
// Completed tasks are removed here to prevent needlessly keeping them
// alive or iterating over them in the future.
currentTask->mDependencies.erase(oldIter);
continue;
}
currentTask = iter->get();
break;
}
}
return currentTask == this ? nullptr : currentTask;
}
TaskController* TaskController::Get() {
MOZ_ASSERT(sSingleton.get());
return sSingleton.get();
}
bool TaskController::Initialize() {
MOZ_ASSERT(!sSingleton);
sSingleton = std::make_unique<TaskController>();
return sSingleton->InitializeInternal();
}
bool TaskController::InitializeInternal() {
mMTProcessingRunnable = NS_NewRunnableFunction(
"TaskController::ExecutePendingMTTasks()",
[]() { TaskController::Get()->ProcessPendingMTTask(); });
mMTBlockingProcessingRunnable = NS_NewRunnableFunction(
"TaskController::ExecutePendingMTTasks()",
[]() { TaskController::Get()->ProcessPendingMTTask(true); });
return true;
}
void TaskController::SetPerformanceCounterState(
PerformanceCounterState* aPerformanceCounterState) {
mPerformanceCounterState = aPerformanceCounterState;
}
/* static */
void TaskController::Shutdown() {
InputTaskManager::Cleanup();
if (sSingleton) {
sSingleton->ShutdownInternal();
}
MOZ_ASSERT(!sSingleton);
}
void TaskController::ShutdownInternal() { sSingleton = nullptr; }
void TaskController::AddTask(already_AddRefed<Task>&& aTask) {
MutexAutoLock lock(mGraphMutex);
RefPtr<Task> task(aTask);
if (TaskManager* manager = task->GetManager()) {
if (manager->mTaskCount == 0) {
mTaskManagers.insert(manager);
}
manager->DidQueueTask();
// Set this here since if this manager's priority modifier doesn't change
// we will not reprioritize when iterating over the queue.
task->mPriorityModifier = manager->mCurrentPriorityModifier;
}
#ifdef MOZ_GECKO_PROFILER
task->mInsertionTime = TimeStamp::Now();
#endif
#ifdef DEBUG
task->mIsInGraph = true;
for (const RefPtr<Task>& otherTask : task->mDependencies) {
MOZ_ASSERT(!otherTask->mTaskManager ||
otherTask->mTaskManager == task->mTaskManager);
}
#endif
LogTask::LogDispatch(task);
auto insertion = mMainThreadTasks.insert(std::move(task));
MOZ_ASSERT(insertion.second);
(*insertion.first)->mIterator = insertion.first;
MaybeInterruptTask(*insertion.first);
}
void TaskController::WaitForTaskOrMessage() {
MutexAutoLock lock(mGraphMutex);
while (!mMayHaveMainThreadTask) {
AUTO_PROFILER_LABEL("TaskController::WaitForTaskOrMessage", IDLE);
mMainThreadCV.Wait();
}
}
void TaskController::ExecuteNextTaskOnlyMainThread() {
MOZ_ASSERT(NS_IsMainThread());
MutexAutoLock lock(mGraphMutex);
ExecuteNextTaskOnlyMainThreadInternal(lock);
}
void TaskController::ProcessPendingMTTask(bool aMayWait) {
MOZ_ASSERT(NS_IsMainThread());
MutexAutoLock lock(mGraphMutex);
for (;;) {
// We only ever process one event here. However we may sometimes
// not actually process a real event because of suspended tasks.
// This loop allows us to wait until we've processed something
// in that scenario.
mMTTaskRunnableProcessedTask = ExecuteNextTaskOnlyMainThreadInternal(lock);
if (mMTTaskRunnableProcessedTask || !aMayWait) {
break;
}
BackgroundHangMonitor().NotifyWait();
{
// ProcessNextEvent will also have attempted to wait, however we may have
// given it a Runnable when all the tasks in our task graph were suspended
// but we weren't able to cheaply determine that.
AUTO_PROFILER_LABEL("TaskController::ProcessPendingMTTask", IDLE);
mMainThreadCV.Wait();
}
BackgroundHangMonitor().NotifyActivity();
}
if (mMayHaveMainThreadTask) {
EnsureMainThreadTasksScheduled();
}
}
void TaskController::ReprioritizeTask(Task* aTask, uint32_t aPriority) {
MutexAutoLock lock(mGraphMutex);
std::set<RefPtr<Task>, Task::PriorityCompare>* queue = &mMainThreadTasks;
MOZ_ASSERT(aTask->mIterator != queue->end());
queue->erase(aTask->mIterator);
aTask->mPriority = aPriority;
auto insertion = queue->insert(aTask);
MOZ_ASSERT(insertion.second);
aTask->mIterator = insertion.first;
MaybeInterruptTask(aTask);
}
// Code supporting runnable compatibility.
// Task that wraps a runnable.
class RunnableTask : public Task {
public:
RunnableTask(already_AddRefed<nsIRunnable>&& aRunnable, int32_t aPriority,
bool aMainThread = true)
: Task(aMainThread, aPriority), mRunnable(aRunnable) {}
virtual bool Run() override {
#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
MOZ_ASSERT(NS_IsMainThread());
// If we're on the main thread, we want to record our current
// runnable's name in a static so that BHR can record it.
Array<char, nsThread::kRunnableNameBufSize> restoreRunnableName;
restoreRunnableName[0] = '\0';
auto clear = MakeScopeExit([&] {
MOZ_ASSERT(NS_IsMainThread());
nsThread::sMainThreadRunnableName = restoreRunnableName;
});
nsAutoCString name;
nsThread::GetLabeledRunnableName(mRunnable, name,
EventQueuePriority(GetPriority()));
restoreRunnableName = nsThread::sMainThreadRunnableName;
// Copy the name into sMainThreadRunnableName's buffer, and append a
// terminating null.
uint32_t length = std::min((uint32_t)nsThread::kRunnableNameBufSize - 1,
(uint32_t)name.Length());
memcpy(nsThread::sMainThreadRunnableName.begin(), name.BeginReading(),
length);
nsThread::sMainThreadRunnableName[length] = '\0';
#endif
mRunnable->Run();
mRunnable = nullptr;
return true;
}
void SetIdleDeadline(TimeStamp aDeadline) override {
nsCOMPtr<nsIIdleRunnable> idleRunnable = do_QueryInterface(mRunnable);
if (idleRunnable) {
idleRunnable->SetDeadline(aDeadline);
}
}
PerformanceCounter* GetPerformanceCounter() const override {
return nsThread::GetPerformanceCounterBase(mRunnable);
}
private:
RefPtr<nsIRunnable> mRunnable;
};
void TaskController::DispatchRunnable(already_AddRefed<nsIRunnable>&& aRunnable,
uint32_t aPriority,
TaskManager* aManager) {
RefPtr<RunnableTask> task = new RunnableTask(std::move(aRunnable), aPriority);
task->SetManager(aManager);
TaskController::Get()->AddTask(task.forget());
}
nsIRunnable* TaskController::GetRunnableForMTTask(bool aReallyWait) {
MutexAutoLock lock(mGraphMutex);
while (mMainThreadTasks.empty()) {
if (!aReallyWait) {
return nullptr;
}
AUTO_PROFILER_LABEL("TaskController::GetRunnableForMTTask::Wait", IDLE);
mMainThreadCV.Wait();
}
return aReallyWait ? mMTBlockingProcessingRunnable : mMTProcessingRunnable;
}
bool TaskController::HasMainThreadPendingTasks() {
auto resetIdleState = MakeScopeExit([&idleManager = mIdleTaskManager] {
if (idleManager) {
idleManager->State().ClearCachedIdleDeadline();
}
});
for (bool considerIdle : {false, true}) {
if (considerIdle && !mIdleTaskManager) {
continue;
}
MutexAutoLock lock(mGraphMutex);
if (considerIdle) {
mIdleTaskManager->State().ForgetPendingTaskGuarantee();
// Temporarily unlock so we can peek our idle deadline.
// XXX We could do this _before_ we take the lock if the API would let us.
// We do want to do this before looking at mMainThreadTasks, in case
// someone adds one while we're unlocked.
{
MutexAutoUnlock unlock(mGraphMutex);
mIdleTaskManager->State().CachePeekedIdleDeadline(unlock);
}
}
// Return early if there's no tasks at all.
if (mMainThreadTasks.empty()) {
return false;
}
// We can cheaply count how many tasks are suspended.
uint64_t totalSuspended = 0;
for (TaskManager* manager : mTaskManagers) {
DebugOnly<bool> modifierChanged =
manager
->UpdateCachesForCurrentIterationAndReportPriorityModifierChanged(
lock, TaskManager::IterationType::NOT_EVENT_LOOP_TURN);
MOZ_ASSERT(!modifierChanged);
// The idle manager should be suspended unless we're doing the idle pass.
MOZ_ASSERT(manager != mIdleTaskManager || manager->mCurrentSuspended ||
considerIdle,
"Why are idle tasks not suspended here?");
if (manager->mCurrentSuspended) {
// XXX - If managers manage off-main-thread tasks this breaks! This
// scenario is explicitly not supported.
//
// This is only incremented inside the lock -or- decremented on the main
// thread so this is safe.
totalSuspended += manager->mTaskCount;
}
}
// Thi would break down if we have a non-suspended task depending on a
// suspended task. This is why for the moment we do not allow tasks
// to be dependent on tasks managed by another taskmanager.
if (mMainThreadTasks.size() > totalSuspended) {
// If mIdleTaskManager->mTaskCount is 0, we never updated the suspended
// state of mIdleTaskManager above, hence shouldn't even check it here.
// But in that case idle tasks are not contributing to our suspended task
// count anyway.
if (mIdleTaskManager && mIdleTaskManager->mTaskCount &&
!mIdleTaskManager->mCurrentSuspended) {
MOZ_ASSERT(considerIdle, "Why is mIdleTaskManager not suspended?");
// Check whether the idle tasks were really needed to make our "we have
// an unsuspended task" decision. If they were, we need to force-enable
// idle tasks until we run our next task.
if (mMainThreadTasks.size() - mIdleTaskManager->mTaskCount <=
totalSuspended) {
mIdleTaskManager->State().EnforcePendingTaskGuarantee();
}
}
return true;
}
}
return false;
}
bool TaskController::ExecuteNextTaskOnlyMainThreadInternal(
const MutexAutoLock& aProofOfLock) {
// Block to make it easier to jump to our cleanup.
bool taskRan = false;
do {
taskRan = DoExecuteNextTaskOnlyMainThreadInternal(aProofOfLock);
if (taskRan) {
break;
}
if (!mIdleTaskManager) {
break;
}
if (mIdleTaskManager->mTaskCount) {
// We have idle tasks that we may not have gotten above because
// our idle state is not up to date. We need to update the idle state
// and try again. We need to temporarily release the lock while we do
// that.
MutexAutoUnlock unlock(mGraphMutex);
mIdleTaskManager->State().UpdateCachedIdleDeadline(unlock);
} else {
MutexAutoUnlock unlock(mGraphMutex);
mIdleTaskManager->State().RanOutOfTasks(unlock);
}
// When we unlocked, someone may have queued a new task on us. So try to
// see whether we can run things again.
taskRan = DoExecuteNextTaskOnlyMainThreadInternal(aProofOfLock);
} while (false);
if (mIdleTaskManager) {
// The pending task guarantee is not needed anymore, since we just tried
// running a task
mIdleTaskManager->State().ForgetPendingTaskGuarantee();
if (mMainThreadTasks.empty()) {
// XXX the IdlePeriodState API demands we have a MutexAutoUnlock for it.
// Otherwise we could perhaps just do this after we exit the locked block,
// by pushing the lock down into this method. Though it's not clear that
// we could check mMainThreadTasks.size() once we unlock, and whether we
// could maybe substitute mMayHaveMainThreadTask for that check.
MutexAutoUnlock unlock(mGraphMutex);
mIdleTaskManager->State().RanOutOfTasks(unlock);
}
}
return taskRan;
}
bool TaskController::DoExecuteNextTaskOnlyMainThreadInternal(
const MutexAutoLock& aProofOfLock) {
nsCOMPtr<nsIThread> mainIThread;
NS_GetMainThread(getter_AddRefs(mainIThread));
nsThread* mainThread = static_cast<nsThread*>(mainIThread.get());
mainThread->SetRunningEventDelay(TimeDuration(), TimeStamp());
uint32_t totalSuspended = 0;
for (TaskManager* manager : mTaskManagers) {
bool modifierChanged =
manager
->UpdateCachesForCurrentIterationAndReportPriorityModifierChanged(
aProofOfLock, TaskManager::IterationType::EVENT_LOOP_TURN);
if (modifierChanged) {
ProcessUpdatedPriorityModifier(manager);
}
if (manager->mCurrentSuspended) {
totalSuspended += manager->mTaskCount;
}
}
MOZ_ASSERT(mMainThreadTasks.size() >= totalSuspended);
// This would break down if we have a non-suspended task depending on a
// suspended task. This is why for the moment we do not allow tasks
// to be dependent on tasks managed by another taskmanager.
if (mMainThreadTasks.size() > totalSuspended) {
for (auto iter = mMainThreadTasks.begin(); iter != mMainThreadTasks.end();
iter++) {
Task* task = iter->get();
if (task->mTaskManager && task->mTaskManager->mCurrentSuspended) {
// Even though we may want to run some dependencies of this task, we
// will run them at their own priority level and not the priority
// level of their dependents.
continue;
}
task = GetFinalDependency(task);
if (!task->IsMainThreadOnly() || task->mInProgress ||
(task->mTaskManager && task->mTaskManager->mCurrentSuspended)) {
continue;
}
mCurrentTasksMT.push(task);
mMainThreadTasks.erase(task->mIterator);
task->mIterator = mMainThreadTasks.end();
task->mInProgress = true;
TaskManager* manager = task->GetManager();
bool result = false;
{
MutexAutoUnlock unlock(mGraphMutex);
if (manager) {
manager->WillRunTask();
if (manager != mIdleTaskManager) {
// Notify the idle period state that we're running a non-idle task.
// This needs to happen while our mutex is not locked!
mIdleTaskManager->State().FlagNotIdle();
} else {
TimeStamp idleDeadline =
mIdleTaskManager->State().GetCachedIdleDeadline();
MOZ_ASSERT(
idleDeadline,
"How can we not have a deadline if our manager is enabled?");
task->SetIdleDeadline(idleDeadline);
}
}
if (mIdleTaskManager) {
// We found a task to run; we can clear the idle deadline on our idle
// task manager. This _must_ be done before we actually run the task,
// because running the task could reenter via spinning the event loop
// and we want to make sure there's no cached idle deadline at that
// point. But we have to make sure we do it after out SetIdleDeadline
// call above, in the case when the task is actually an idle task.
mIdleTaskManager->State().ClearCachedIdleDeadline();
}
TimeStamp now = TimeStamp::Now();
#ifdef MOZ_GECKO_PROFILER
if (task->GetPriority() < uint32_t(EventQueuePriority::InputHigh)) {
mainThread->SetRunningEventDelay(TimeDuration(), now);
} else {
mainThread->SetRunningEventDelay(now - task->mInsertionTime, now);
}
#endif
PerformanceCounterState::Snapshot snapshot =
mPerformanceCounterState->RunnableWillRun(
task->GetPerformanceCounter(), now,
manager == mIdleTaskManager);
{
LogTask::Run log(task);
result = task->Run();
}
// Task itself should keep manager alive.
if (manager) {
manager->DidRunTask();
}
mPerformanceCounterState->RunnableDidRun(std::move(snapshot));
}
// Task itself should keep manager alive.
if (manager && result && manager->mTaskCount == 0) {
mTaskManagers.erase(manager);
}
task->mInProgress = false;
if (!result) {
// Presumably this task was interrupted, leave its dependencies
// unresolved and reinsert into the queue.
auto insertion =
mMainThreadTasks.insert(std::move(mCurrentTasksMT.top()));
MOZ_ASSERT(insertion.second);
task->mIterator = insertion.first;
manager->WillRunTask();
} else {
task->mCompleted = true;
#ifdef DEBUG
task->mIsInGraph = false;
#endif
// Clear dependencies to release references.
task->mDependencies.clear();
}
mCurrentTasksMT.pop();
return true;
}
}
mMayHaveMainThreadTask = false;
if (mIdleTaskManager) {
// We did not find a task to run. We still need to clear the cached idle
// deadline on our idle state, because that deadline was only relevant to
// the execution of this function. Had we found a task, we would have
// cleared the deadline before running that task.
mIdleTaskManager->State().ClearCachedIdleDeadline();
}
return false;
}
Task* TaskController::GetFinalDependency(Task* aTask) {
Task* nextTask;
while ((nextTask = aTask->GetHighestPriorityDependency())) {
aTask = nextTask;
}
return aTask;
}
void TaskController::MaybeInterruptTask(Task* aTask) {
mGraphMutex.AssertCurrentThreadOwns();
if (!aTask) {
return;
}
// This optimization prevents many slow lookups in long chains of similar
// priority.
if (!aTask->mDependencies.empty()) {
Task* firstDependency = aTask->mDependencies.begin()->get();
if (aTask->GetPriority() <= firstDependency->GetPriority() &&
!firstDependency->mCompleted &&
aTask->IsMainThreadOnly() == firstDependency->IsMainThreadOnly()) {
// This task has the same or a higher priority as one of its dependencies,
// never any need to interrupt.
return;
}
}
Task* finalDependency = GetFinalDependency(aTask);
if (finalDependency->mInProgress) {
// No need to wake anything, we can't schedule this task right now anyway.
return;
}
EnsureMainThreadTasksScheduled();
mMayHaveMainThreadTask = true;
if (mCurrentTasksMT.empty()) {
return;
}
// We could go through the steps above here and interrupt an off main
// thread task in case it has a lower priority.
if (!finalDependency->IsMainThreadOnly()) {
return;
}
if (mCurrentTasksMT.top()->GetPriority() < aTask->GetPriority()) {
mCurrentTasksMT.top()->RequestInterrupt(aTask->GetPriority());
}
}
Task* TaskController::GetHighestPriorityMTTask() {
mGraphMutex.AssertCurrentThreadOwns();
if (!mMainThreadTasks.empty()) {
return mMainThreadTasks.begin()->get();
}
return nullptr;
}
void TaskController::EnsureMainThreadTasksScheduled() {
if (mObserver) {
mObserver->OnDispatchedEvent();
}
if (mExternalCondVar) {
mExternalCondVar->Notify();
}
mMainThreadCV.Notify();
}
void TaskController::ProcessUpdatedPriorityModifier(TaskManager* aManager) {
mGraphMutex.AssertCurrentThreadOwns();
MOZ_ASSERT(NS_IsMainThread());
int32_t modifier = aManager->mCurrentPriorityModifier;
std::vector<RefPtr<Task>> storedTasks;
// Find all relevant tasks.
for (auto iter = mMainThreadTasks.begin(); iter != mMainThreadTasks.end();) {
if ((*iter)->mTaskManager == aManager) {
storedTasks.push_back(*iter);
iter = mMainThreadTasks.erase(iter);
} else {
iter++;
}
}
// Reinsert found tasks with their new priorities.
for (RefPtr<Task>& ref : storedTasks) {
// Kept alive at first by the vector and then by mMainThreadTasks.
Task* task = ref;
task->mPriorityModifier = modifier;
auto insertion = mMainThreadTasks.insert(std::move(ref));
MOZ_ASSERT(insertion.second);
task->mIterator = insertion.first;
}
}
} // namespace mozilla