List<Task> taskList = new List<Task>();
//声明CancellationTokenSource对象
CancellationTokenSource cancelTokenSource = new CancellationTokenSource(); ;
TaskFactory taskFactory = new TaskFactory(new LimitedConcurrencyLevelTaskScheduler(Environment.ProcessorCount * 4));
taskList.Add(
taskFactory.StartNew(s =>
{
}, null, cancelTokenSource.Token)
);
//当taskList中执行完所有任务时，非阻塞式的回调
taskList.Add(taskFactory.ContinueWhenAll(taskList.ToArray(), rArray =>
{
if (taskList != null)
{
taskList.Clear();
}
if (ValidationAnalysisWindow.cancelTokenSource.IsCancellationRequested)
{
return;
}
}));
public class LimitedConcurrencyLevelTaskScheduler : TaskScheduler
{
/// <summary>Whether the current thread is processing work items.</summary>
[ThreadStatic]
private static bool _currentThreadIsProcessingItems;
/// <summary>The list of tasks to be executed.</summary>
private readonly LinkedList<Task> _tasks = new LinkedList<Task>(); // protected by lock(_tasks)
/// <summary>The maximum concurrency level allowed by this scheduler.</summary>
private readonly int _maxDegreeOfParallelism;
/// <summary>Whether the scheduler is currently processing work items.</summary>
private int _delegatesQueuedOrRunning = 0; // protected by lock(_tasks)
/// <summary>
/// Initializes an instance of the LimitedConcurrencyLevelTaskScheduler class with the
/// specified degree of parallelism.
/// </summary>
/// <param name="maxDegreeOfParallelism">The maximum degree of parallelism provided by this scheduler.</param>
public LimitedConcurrencyLevelTaskScheduler(int maxDegreeOfParallelism)
{
if (maxDegreeOfParallelism < 1) throw new ArgumentOutOfRangeException("maxDegreeOfParallelism");
_maxDegreeOfParallelism = maxDegreeOfParallelism;
}
/// <summary>
/// current executing number;
/// </summary>
public int CurrentCount { get; set; }
/// <summary>Queues a task to the scheduler.</summary>
/// <param name="task">The task to be queued.</param>
protected sealed override void QueueTask(Task task)
{
// Add the task to the list of tasks to be processed. If there aren't enough
// delegates currently queued or running to process tasks, schedule another.
lock (_tasks)
{
//Debug.WriteLine("Task Count : {0} ", _tasks.Count);
_tasks.AddLast(task);
if (_delegatesQueuedOrRunning < _maxDegreeOfParallelism)
{
++_delegatesQueuedOrRunning;
NotifyThreadPoolOfPendingWork();
}
}
}
//int executingCount = 0;
private static object executeLock = new object();
/// <summary>
/// Informs the ThreadPool that there's work to be executed for this scheduler.
/// </summary>
private void NotifyThreadPoolOfPendingWork()
{
ThreadPool.UnsafeQueueUserWorkItem(_ =>
{
// Note that the current thread is now processing work items.
// This is necessary to enable inlining of tasks into this thread.
_currentThreadIsProcessingItems = true;
try
{
// Process all available items in the queue.
while (true)
{
Task item;
lock (_tasks)
{
// When there are no more items to be processed,
// note that we're done processing, and get out.
if (_tasks.Count == 0)
{
--_delegatesQueuedOrRunning;
break;
}
// Get the next item from the queue
item = _tasks.First.Value;
_tasks.RemoveFirst();
}
// Execute the task we pulled out of the queue
base.TryExecuteTask(item);
}
}
// We're done processing items on the current thread
finally { _currentThreadIsProcessingItems = false; }
}, null);
}
/// <summary>Attempts to execute the specified task on the current thread.</summary>
/// <param name="task">The task to be executed.</param>
/// <param name="taskWasPreviouslyQueued"></param>
/// <returns>Whether the task could be executed on the current thread.</returns>
protected sealed override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
{
// If this thread isn't already processing a task, we don't support inlining
if (!_currentThreadIsProcessingItems) return false;
// If the task was previously queued, remove it from the queue
if (taskWasPreviouslyQueued) TryDequeue(task);
// Try to run the task.
return base.TryExecuteTask(task);
}
/// <summary>Attempts to remove a previously scheduled task from the scheduler.</summary>
/// <param name="task">The task to be removed.</param>
/// <returns>Whether the task could be found and removed.</returns>
protected sealed override bool TryDequeue(Task task)
{
lock (_tasks) return _tasks.Remove(task);
}
/// <summary>Gets the maximum concurrency level supported by this scheduler.</summary>
public sealed override int MaximumConcurrencyLevel { get { return _maxDegreeOfParallelism; } }
/// <summary>Gets an enumerable of the tasks currently scheduled on this scheduler.</summary>
/// <returns>An enumerable of the tasks currently scheduled.</returns>
protected sealed override IEnumerable<Task> GetScheduledTasks()
{
bool lockTaken = false;
try
{
Monitor.TryEnter(_tasks, ref lockTaken);
if (lockTaken) return _tasks.ToArray();
else throw new NotSupportedException();
}
finally
{
if (lockTaken) Monitor.Exit(_tasks);
}
}
}
