C# Task 源代码（2）

 [SecuritySafeCritical] // Needed for QueueTask
        internal void ScheduleAndStart(bool needsProtection)
        {
            Contract.Assert(m_taskScheduler != null, "expected a task scheduler to have been selected");
            Contract.Assert((m_stateFlags & TASK_STATE_STARTED) == 0, "task has already started");

            // Set the TASK_STATE_STARTED bit
            if (needsProtection)
            {
                if (!MarkStarted())
                {
                    // A cancel has snuck in before we could get started.  Quietly exit.
                    return;
                }
            }
            else
            {
                m_stateFlags |= TASK_STATE_STARTED;
            }

            if (s_asyncDebuggingEnabled)
            {
                AddToActiveTasks(this);
            }

            if (AsyncCausalityTracer.LoggingOn && (Options & (TaskCreationOptions)InternalTaskOptions.ContinuationTask) == 0)
            {
                //For all other task than TaskContinuations we want to log. TaskContinuations log in their constructor
                AsyncCausalityTracer.TraceOperationCreation(CausalityTraceLevel.Required, this.Id, "Task: "+((Delegate)m_action).Method.Name, 0);
            }


            try
            {
                // Queue to the indicated scheduler.
                m_taskScheduler.InternalQueueTask(this);
            }
            catch (ThreadAbortException tae)
            {
                AddException(tae);
                FinishThreadAbortedTask(true, false);
            }
            catch (Exception e)
            {
                // The scheduler had a problem queueing this task.  Record the exception, leaving this task in
                // a Faulted state.
                TaskSchedulerException tse = new TaskSchedulerException(e);
                AddException(tse);
                Finish(false);

                // Now we need to mark ourselves as "handled" to avoid crashing the finalizer thread if we are called from StartNew()
                // or from the self replicating logic, because in both cases the exception is either propagated outside directly, or added
                // to an enclosing parent. However we won‘t do this for continuation tasks, because in that case we internally eat the exception
                // and therefore we need to make sure the user does later observe it explicitly or see it on the finalizer.

                if ((Options & (TaskCreationOptions)InternalTaskOptions.ContinuationTask) == 0)
                {
                    // m_contingentProperties.m_exceptionsHolder *should* already exist after AddException()
                    Contract.Assert(
                        (m_contingentProperties != null) &&
                        (m_contingentProperties.m_exceptionsHolder != null) &&
                        (m_contingentProperties.m_exceptionsHolder.ContainsFaultList),
                            "Task.ScheduleAndStart(): Expected m_contingentProperties.m_exceptionsHolder to exist " +
                            "and to have faults recorded.");

                    m_contingentProperties.m_exceptionsHolder.MarkAsHandled(false);
                }
                // re-throw the exception wrapped as a TaskSchedulerException.
                throw tse;
            }
        }

  // This dictonary relates the task id, from an operation id located in the Async Causality log to the actual
        // task. This is to be used by the debugger ONLY. Task in this dictionary represent current active tasks.
        private static readonly Dictionary<int, Task> s_currentActiveTasks = new Dictionary<int, Task>();
 [FriendAccessAllowed]
        internal static bool AddToActiveTasks(Task task)
        {
            Contract.Requires(task != null, "Null Task objects can‘t be added to the ActiveTasks collection");
            lock (s_activeTasksLock)
            {
                s_currentActiveTasks[task.Id] = task;
            }
            //always return true to keep signature as bool for backwards compatibility
            return true;
        }

 [SecurityCritical]
        internal void InternalQueueTask(Task task)
        {
            Contract.Requires(task != null);

            task.FireTaskScheduledIfNeeded(this);

            this.QueueTask(task);
        }
 [SecurityCritical]
        protected internal override void QueueTask(Task task)
        {
            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);
            }
        }

  [SecurityCritical]
        protected internal override bool TryDequeue(Task task)
        {
            // just delegate to TP
            return ThreadPool.TryPopCustomWorkItem(task);
        }

        [SecurityCritical]
        protected override IEnumerable<Task> GetScheduledTasks()
        {
            return FilterTasksFromWorkItems(ThreadPool.GetQueuedWorkItems());
        }

        /// <summary>
        /// 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.
        /// </summary>
        [SecurityCritical]
        protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
        {

        -----------------------
        }