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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / BCL / System / Threading / Tasks / ThreadPoolTaskScheduler.cs / 1305376 / ThreadPoolTaskScheduler.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // TaskScheduler.cs // //[....] // // This file contains the primary interface and management of tasks and queues. // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System; using System.Security; using System.Diagnostics.Contracts; using System.Collections.Generic; using System.Text; using System.Diagnostics.Eventing; namespace System.Threading.Tasks { ////// An implementation of TaskScheduler that uses the ThreadPool scheduler /// internal sealed class ThreadPoolTaskScheduler: TaskScheduler { ////// Constructs a new ThreadPool task scheduler object /// internal ThreadPoolTaskScheduler() { } // static delegate for threads allocated to handle LongRunning tasks. private static ParameterizedThreadStart s_longRunningThreadWork = new ParameterizedThreadStart(LongRunningThreadWork); private static void LongRunningThreadWork(object obj) { Task t = obj as Task; Contract.Assert(t != null, "TaskScheduler.LongRunningThreadWork: t is null"); t.ExecuteEntry(false); } ////// Schedules a task to the ThreadPool. /// /// The task to schedule. [SecurityCritical] protected internal override void QueueTask(Task task) { #if !FEATURE_PAL // PAL doesn't support eventing if (TplEtwProvider.Log.IsEnabled(EventLevel.Verbose, ((EventKeywords)(-1)))) { Task currentTask = Task.InternalCurrent; Task creatingTask = task.m_parent; TplEtwProvider.Log.TaskScheduled(this.Id, currentTask == null ? 0 : currentTask.Id, task.Id, creatingTask == null? 0 : creatingTask.Id, (int) task.Options); } #endif if ((task.Options & TaskCreationOptions.LongRunning) != 0) { // Run LongRunning tasks on their own dedicated thread. Thread thread = new Thread(s_longRunningThreadWork); thread.IsBackground = true; // Keep this thread from blocking process shutdown thread.Start(task); } else { // Normal handling for non-LongRunning tasks. bool forceToGlobalQueue = ((task.Options & TaskCreationOptions.PreferFairness) != 0); ThreadPool.UnsafeQueueCustomWorkItem(task, forceToGlobalQueue); } } ////// This internal function will do this: /// (1) If the task had previously been queued, attempt to pop it and return false if that fails. /// (2) Propagate the return value from Task.ExecuteEntry() back to the caller. /// /// IMPORTANT NOTE: TryExecuteTaskInline will NOT throw task exceptions itself. Any wait code path using this function needs /// to account for exceptions that need to be propagated, and throw themselves accordingly. /// [SecurityCritical] protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued) { // If the task was previously scheduled, and we can't pop it, then return false. if (taskWasPreviouslyQueued && !ThreadPool.TryPopCustomWorkItem(task)) return false; // Propagate the return value of Task.ExecuteEntry() bool rval = false; try { rval = task.ExecuteEntry(false); // calling the TaskBase override here, because it handles switching Task.Current etc. } finally { // Only call NWIP() if task was previously queued if(taskWasPreviouslyQueued) NotifyWorkItemProgress(); } return rval; } [SecurityCritical] protected internal override bool TryDequeue(Task task) { // just delegate to TP return ThreadPool.TryPopCustomWorkItem(task); } [SecurityCritical] protected override IEnumerableGetScheduledTasks() { return FilterTasksFromWorkItems(ThreadPool.GetQueuedWorkItems()); } private IEnumerable FilterTasksFromWorkItems(IEnumerable tpwItems) { foreach (IThreadPoolWorkItem tpwi in tpwItems) { if (tpwi is Task) { yield return (Task)tpwi; } } } /// /// Notifies the scheduler that work is progressing (no-op). /// internal override void NotifyWorkItemProgress() { ThreadPool.NotifyWorkItemProgress(); } ////// This is the only scheduler that returns false for this property, indicating that the task entry codepath is unsafe (CAS free) /// since we know that the underlying scheduler already takes care of atomic transitions from queued to non-queued. /// internal override bool RequiresAtomicStartTransition { get { return false; } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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