From 36d22d82aa202bb199967e9512281e9a53db42c9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 21:33:14 +0200 Subject: Adding upstream version 115.7.0esr. Signed-off-by: Daniel Baumann --- xpcom/threads/TaskController.h | 445 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 445 insertions(+) create mode 100644 xpcom/threads/TaskController.h (limited to 'xpcom/threads/TaskController.h') diff --git a/xpcom/threads/TaskController.h b/xpcom/threads/TaskController.h new file mode 100644 index 0000000000..184080002a --- /dev/null +++ b/xpcom/threads/TaskController.h @@ -0,0 +1,445 @@ +/* -*- 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/. */ + +#ifndef mozilla_TaskController_h +#define mozilla_TaskController_h + +#include "MainThreadUtils.h" +#include "mozilla/CondVar.h" +#include "mozilla/IdlePeriodState.h" +#include "mozilla/RefPtr.h" +#include "mozilla/Mutex.h" +#include "mozilla/StaticMutex.h" +#include "mozilla/TimeStamp.h" +#include "mozilla/EventQueue.h" +#include "nsISupportsImpl.h" +#include "nsIEventTarget.h" + +#include +#include +#include +#include +#include +#include + +class nsIRunnable; +class nsIThreadObserver; + +namespace mozilla { + +class Task; +class TaskController; +class PerformanceCounter; +class PerformanceCounterState; + +const EventQueuePriority kDefaultPriorityValue = EventQueuePriority::Normal; + +// This file contains the core classes to access the Gecko scheduler. The +// scheduler forms a graph of prioritize tasks, and is responsible for ensuring +// the execution of tasks or their dependencies in order of inherited priority. +// +// The core class is the 'Task' class. The task class describes a single unit of +// work. Users scheduling work implement this class and are required to +// reimplement the 'Run' function in order to do work. +// +// The TaskManager class is reimplemented by users that require +// the ability to reprioritize or suspend tasks. +// +// The TaskController is responsible for scheduling the work itself. The AddTask +// function is used to schedule work. The ReprioritizeTask function may be used +// to change the priority of a task already in the task graph, without +// unscheduling it. + +// The TaskManager is the baseclass used to atomically manage a large set of +// tasks. API users reimplementing TaskManager may reimplement a number of +// functions that they may use to indicate to the scheduler changes in the state +// for any tasks they manage. They may be used to reprioritize or suspend tasks +// under their control, and will also be notified before and after tasks under +// their control are executed. Their methods will only be called once per event +// loop turn, however they may still incur some performance overhead. In +// addition to this frequent reprioritizations may incur a significant +// performance overhead and are discouraged. A TaskManager may currently only be +// used to manage tasks that are bound to the Gecko Main Thread. +class TaskManager { + public: + NS_INLINE_DECL_THREADSAFE_REFCOUNTING(TaskManager) + + TaskManager() : mTaskCount(0) {} + + // Subclasses implementing task manager will have this function called to + // determine whether their associated tasks are currently suspended. This + // will only be called once per iteration of the task queue, this means that + // suspension of tasks managed by a single TaskManager may be assumed to + // occur atomically. + virtual bool IsSuspended(const MutexAutoLock& aProofOfLock) { return false; } + + // Subclasses may implement this in order to supply a priority adjustment + // to their managed tasks. This is called once per iteration of the task + // queue, and may be assumed to occur atomically for all managed tasks. + virtual int32_t GetPriorityModifierForEventLoopTurn( + const MutexAutoLock& aProofOfLock) { + return 0; + } + + void DidQueueTask() { ++mTaskCount; } + // This is called when a managed task is about to be executed by the + // scheduler. Anyone reimplementing this should ensure to call the parent or + // decrement mTaskCount. + virtual void WillRunTask() { --mTaskCount; } + // This is called when a managed task has finished being executed by the + // scheduler. + virtual void DidRunTask() {} + uint32_t PendingTaskCount() { return mTaskCount; } + + protected: + virtual ~TaskManager() {} + + private: + friend class TaskController; + + enum class IterationType { NOT_EVENT_LOOP_TURN, EVENT_LOOP_TURN }; + bool UpdateCachesForCurrentIterationAndReportPriorityModifierChanged( + const MutexAutoLock& aProofOfLock, IterationType aIterationType); + + bool mCurrentSuspended = false; + int32_t mCurrentPriorityModifier = 0; + + std::atomic mTaskCount; +}; + +// A Task is the the base class for any unit of work that may be scheduled. +// Subclasses may specify their priority and whether they should be bound to +// the Gecko Main thread. When not bound to the main thread tasks may be +// executed on any available thread (including the main thread), but they may +// also be executed in parallel to any other task they do not have a dependency +// relationship with. Tasks will be run in order of object creation. +class Task { + public: + NS_INLINE_DECL_THREADSAFE_REFCOUNTING(Task) + + bool IsMainThreadOnly() { return mMainThreadOnly; } + + // This returns the current task priority with its modifier applied. + uint32_t GetPriority() { return mPriority + mPriorityModifier; } + uint64_t GetSeqNo() { return mSeqNo; } + + // Callee needs to assume this may be called on any thread. + // aInterruptPriority passes the priority of the higher priority task that + // is ready to be executed. The task may safely ignore this function, or + // interrupt any work being done. It may return 'false' from its run function + // in order to be run automatically in the future, or true if it will + // reschedule incomplete work manually. + virtual void RequestInterrupt(uint32_t aInterruptPriority) {} + + // At the moment this -must- be called before the task is added to the + // controller. Calling this after tasks have been added to the controller + // results in undefined behavior! + // At submission, tasks must depend only on tasks managed by the same, or + // no idle manager. + void AddDependency(Task* aTask) { + MOZ_ASSERT(aTask); + MOZ_ASSERT(!mIsInGraph); + mDependencies.insert(aTask); + } + + // This sets the TaskManager for the current task. Calling this after the + // task has been added to the TaskController results in undefined behavior. + void SetManager(TaskManager* aManager) { + MOZ_ASSERT(mMainThreadOnly); + MOZ_ASSERT(!mIsInGraph); + mTaskManager = aManager; + } + TaskManager* GetManager() { return mTaskManager; } + + struct PriorityCompare { + bool operator()(const RefPtr& aTaskA, + const RefPtr& aTaskB) const { + uint32_t prioA = aTaskA->GetPriority(); + uint32_t prioB = aTaskB->GetPriority(); + return (prioA > prioB) || + (prioA == prioB && (aTaskA->GetSeqNo() < aTaskB->GetSeqNo())); + } + }; + + // Tell the task about its idle deadline. Will only be called for + // tasks managed by an IdleTaskManager, right before the task runs. + virtual void SetIdleDeadline(TimeStamp aDeadline) {} + + virtual PerformanceCounter* GetPerformanceCounter() const { return nullptr; } + + // Get a name for this task. This returns false if the task has no name. +#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY + virtual bool GetName(nsACString& aName) = 0; +#else + virtual bool GetName(nsACString& aName) { return false; } +#endif + + protected: + Task(bool aMainThreadOnly, + uint32_t aPriority = static_cast(kDefaultPriorityValue)) + : mMainThreadOnly(aMainThreadOnly), + mSeqNo(sCurrentTaskSeqNo++), + mPriority(aPriority) {} + + Task(bool aMainThreadOnly, + EventQueuePriority aPriority = kDefaultPriorityValue) + : mMainThreadOnly(aMainThreadOnly), + mSeqNo(sCurrentTaskSeqNo++), + mPriority(static_cast(aPriority)) {} + + virtual ~Task() {} + + friend class TaskController; + + // When this returns false, the task is considered incomplete and will be + // rescheduled at the current 'mPriority' level. + virtual bool Run() = 0; + + private: + Task* GetHighestPriorityDependency(); + + // Iterator pointing to this task's position in + // mThreadableTasks/mMainThreadTasks if, and only if this task is currently + // scheduled to be executed. This allows fast access to the task's position + // in the set, allowing for fast removal. + // This is safe, and remains valid unless the task is removed from the set. + // See also iterator invalidation in: + // https://en.cppreference.com/w/cpp/container + // + // Or the spec: + // "All Associative Containers: The insert and emplace members shall not + // affect the validity of iterators and references to the container + // [26.2.6/9]" "All Associative Containers: The erase members shall invalidate + // only iterators and references to the erased elements [26.2.6/9]" + std::set, PriorityCompare>::iterator mIterator; + std::set, PriorityCompare> mDependencies; + + RefPtr mTaskManager; + + // Access to these variables is protected by the GraphMutex. + bool mMainThreadOnly; + bool mCompleted = false; + bool mInProgress = false; +#ifdef DEBUG + bool mIsInGraph = false; +#endif + + static std::atomic sCurrentTaskSeqNo; + int64_t mSeqNo; + uint32_t mPriority; + // Modifier currently being applied to this task by its taskmanager. + int32_t mPriorityModifier = 0; + // Time this task was inserted into the task graph, this is used by the + // profiler. + mozilla::TimeStamp mInsertionTime; +}; + +struct PoolThread { + PRThread* mThread; + RefPtr mCurrentTask; + // This may be higher than mCurrentTask's priority due to priority + // propagation. This is -only- valid when mCurrentTask != nullptr. + uint32_t mEffectiveTaskPriority; +}; + +// A task manager implementation for priority levels that should only +// run during idle periods. +class IdleTaskManager : public TaskManager { + public: + explicit IdleTaskManager(already_AddRefed&& aIdlePeriod) + : mIdlePeriodState(std::move(aIdlePeriod)), mProcessedTaskCount(0) {} + + IdlePeriodState& State() { return mIdlePeriodState; } + + bool IsSuspended(const MutexAutoLock& aProofOfLock) override { + TimeStamp idleDeadline = State().GetCachedIdleDeadline(); + return !idleDeadline; + } + + void DidRunTask() override { + TaskManager::DidRunTask(); + ++mProcessedTaskCount; + } + + uint64_t ProcessedTaskCount() { return mProcessedTaskCount; } + + private: + // Tracking of our idle state of various sorts. + IdlePeriodState mIdlePeriodState; + + std::atomic mProcessedTaskCount; +}; + +// The TaskController is the core class of the scheduler. It is used to +// schedule tasks to be executed, as well as to reprioritize tasks that have +// already been scheduled. The core functions to do this are AddTask and +// ReprioritizeTask. +class TaskController { + public: + TaskController(); + + static TaskController* Get(); + + static void Initialize(); + + void SetThreadObserver(nsIThreadObserver* aObserver) { + MutexAutoLock lock(mGraphMutex); + mObserver = aObserver; + } + void SetConditionVariable(CondVar* aExternalCondVar) { + MutexAutoLock lock(mGraphMutex); + mExternalCondVar = aExternalCondVar; + } + + void SetIdleTaskManager(IdleTaskManager* aIdleTaskManager) { + mIdleTaskManager = aIdleTaskManager; + } + IdleTaskManager* GetIdleTaskManager() { return mIdleTaskManager.get(); } + + uint64_t RunOutOfMTTasksCount() { return mRunOutOfMTTasksCounter; } + + // Initialization and shutdown code. + void SetPerformanceCounterState( + PerformanceCounterState* aPerformanceCounterState); + + static void Shutdown(); + + // This adds a task to the TaskController graph. + // This may be called on any thread. + void AddTask(already_AddRefed&& aTask); + + // This wait function is the theoretical function you would need if our main + // thread needs to also process OS messages or something along those lines. + void WaitForTaskOrMessage(); + + // This gets the next (highest priority) task that is only allowed to execute + // on the main thread. + void ExecuteNextTaskOnlyMainThread(); + + // Process all pending main thread tasks. + void ProcessPendingMTTask(bool aMayWait = false); + + // This allows reprioritization of a task already in the task graph. + // This may be called on any thread. + void ReprioritizeTask(Task* aTask, uint32_t aPriority); + + void DispatchRunnable(already_AddRefed&& aRunnable, + uint32_t aPriority, TaskManager* aManager = nullptr); + + nsIRunnable* GetRunnableForMTTask(bool aReallyWait); + + bool HasMainThreadPendingTasks(); + + uint64_t PendingMainthreadTaskCountIncludingSuspended(); + + // Let users know whether the last main thread task runnable did work. + bool MTTaskRunnableProcessedTask() { + MOZ_ASSERT(NS_IsMainThread()); + return mMTTaskRunnableProcessedTask; + } + + static int32_t GetPoolThreadCount(); + static size_t GetThreadStackSize(); + + private: + friend void ThreadFuncPoolThread(void* aIndex); + + void InitializeThreadPool(); + + // This gets the next (highest priority) task that is only allowed to execute + // on the main thread, if any, and executes it. + // Returns true if it succeeded. + bool ExecuteNextTaskOnlyMainThreadInternal(const MutexAutoLock& aProofOfLock); + + // The guts of ExecuteNextTaskOnlyMainThreadInternal, which get idle handling + // wrapped around them. Returns whether a task actually ran. + bool DoExecuteNextTaskOnlyMainThreadInternal( + const MutexAutoLock& aProofOfLock); + + Task* GetFinalDependency(Task* aTask); + void MaybeInterruptTask(Task* aTask); + Task* GetHighestPriorityMTTask(); + + void EnsureMainThreadTasksScheduled(); + + void ProcessUpdatedPriorityModifier(TaskManager* aManager); + + void ShutdownThreadPoolInternal(); + void ShutdownInternal(); + + void RunPoolThread(); + + static std::unique_ptr sSingleton; + static StaticMutex sSingletonMutex MOZ_UNANNOTATED; + + // This protects access to the task graph. + Mutex mGraphMutex MOZ_UNANNOTATED; + + // This protects thread pool initialization. We cannot do this from within + // the GraphMutex, since thread creation on Windows can generate events on + // the main thread that need to be handled. + Mutex mPoolInitializationMutex = + Mutex("TaskController::mPoolInitializationMutex"); + // Created under the PoolInitialization mutex, then never extended, and + // only freed when the object is freed. mThread is set at creation time; + // mCurrentTask and mEffectiveTaskPriority are only accessed from the + // thread, so no locking is needed to access this. + std::vector mPoolThreads; + + CondVar mThreadPoolCV; + CondVar mMainThreadCV; + + // Variables below are protected by mGraphMutex. + + std::stack> mCurrentTasksMT; + + // A list of all tasks ordered by priority. + std::set, Task::PriorityCompare> mThreadableTasks; + std::set, Task::PriorityCompare> mMainThreadTasks; + + // TaskManagers currently active. + // We can use a raw pointer since tasks always hold on to their TaskManager. + std::set mTaskManagers; + + // This ensures we keep running the main thread if we processed a task there. + bool mMayHaveMainThreadTask = true; + bool mShuttingDown = false; + + // This stores whether the last main thread task runnable did work. + // Accessed only on MainThread + bool mMTTaskRunnableProcessedTask = false; + + // Whether our thread pool is initialized. We use this currently to avoid + // starting the threads in processes where it's never used. This is protected + // by mPoolInitializationMutex. + bool mThreadPoolInitialized = false; + + // Whether we have scheduled a runnable on the main thread event loop. + // This is used for nsIRunnable compatibility. + RefPtr mMTProcessingRunnable; + RefPtr mMTBlockingProcessingRunnable; + + // XXX - Thread observer to notify when a new event has been dispatched + // Set immediately, then simply accessed from any thread + nsIThreadObserver* mObserver = nullptr; + // XXX - External condvar to notify when we have received an event + CondVar* mExternalCondVar = nullptr; + // Idle task manager so we can properly do idle state stuff. + RefPtr mIdleTaskManager; + + // How many times the main thread was empty. + std::atomic mRunOutOfMTTasksCounter; + + // Our tracking of our performance counter and long task state, + // shared with nsThread. + // Set once when MainThread is created, never changed, only accessed from + // DoExecuteNextTaskOnlyMainThreadInternal() + PerformanceCounterState* mPerformanceCounterState = nullptr; +}; + +} // namespace mozilla + +#endif // mozilla_TaskController_h -- cgit v1.2.3