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// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
//
// QueryTask.cs
//
// <OWNER>Microsoft</OWNER>
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
using System.Threading;
using System.Threading.Tasks;
using System.Diagnostics.Contracts;
namespace System.Linq.Parallel
{
// To disable exception marshaling (e.g. for debugging purposes), uncomment this symbol
// or recompile PLINQ passing the symbol on the cmd-line, i.e. csc.exe ... /d:LET_...
//#define LET_ASYNC_EXCEPTIONS_CRASH
/// <summary>
/// Simple abstract task representation, allowing either synchronous and asynchronous
/// execution. Subclasses override the Work API to implement the logic.
/// </summary>
internal abstract class QueryTask
{
protected int m_taskIndex; // The unique id of this task.
protected QueryTaskGroupState m_groupState; // State shared among the tasks.
//-----------------------------------------------------------------------------------
// Constructs a new task with the specified shared state.
//
protected QueryTask(int taskIndex, QueryTaskGroupState groupState)
{
Contract.Assert(groupState != null);
m_taskIndex = taskIndex;
m_groupState = groupState;
}
//-----------------------------------------------------------------------------------
// A static function used by s_runTaskSynchronouslyDelegate, which is used by RunSynchronously
//
private static void RunTaskSynchronously(object o)
{
((QueryTask)o).BaseWork(null);
}
//-----------------------------------------------------------------------------------
// A static delegate used by RunSynchronously
//
private static Action<object> s_runTaskSynchronouslyDelegate = RunTaskSynchronously;
//-----------------------------------------------------------------------------------
// Executes the task synchronously (on the current thread).
//
internal Task RunSynchronously(TaskScheduler taskScheduler)
{
Contract.Assert(taskScheduler == TaskScheduler.Default, "PLINQ queries can currently execute only on the default scheduler.");
TraceHelpers.TraceInfo("[timing]: {0}: Running work synchronously", DateTime.Now.Ticks, m_taskIndex);
Task task = new Task(s_runTaskSynchronouslyDelegate, this, TaskCreationOptions.AttachedToParent);
task.RunSynchronously(taskScheduler);
return task;
}
//-----------------------------------------------------------------------------------
// Executes the task asynchronously (elsewhere, unspecified).
//
private static Action<object> s_baseWorkDelegate = delegate(object o)
{
((QueryTask)o).BaseWork(null);
};
internal Task RunAsynchronously(TaskScheduler taskScheduler)
{
Contract.Assert(taskScheduler == TaskScheduler.Default, "PLINQ queries can currently execute only on the default scheduler.");
TraceHelpers.TraceInfo("[timing]: {0}: Queue work {1} to occur asynchronously", DateTime.Now.Ticks, m_taskIndex);
return Task.Factory.StartNew(s_baseWorkDelegate, this, new CancellationToken(), TaskCreationOptions.AttachedToParent | TaskCreationOptions.PreferFairness, taskScheduler);
}
//-----------------------------------------------------------------------------------
// Common function called regardless of sync or async execution. Just wraps some
// amount of tracing around the call to the real work API.
//
private void BaseWork(object unused)
{
Contract.Assert(unused == null);
TraceHelpers.TraceInfo("[timing]: {0}: Start work {1}", DateTime.Now.Ticks, m_taskIndex);
#if !FEATURE_PAL && !SILVERLIGHT // PAL doesn't support eventing
PlinqEtwProvider.Log.ParallelQueryFork(m_groupState.QueryId);
#endif
try
{
Work();
}
finally
{
#if !FEATURE_PAL && !SILVERLIGHT // PAL doesn't support eventing
PlinqEtwProvider.Log.ParallelQueryJoin(m_groupState.QueryId);
#endif
}
TraceHelpers.TraceInfo("[timing]: {0}: End work {1}", DateTime.Now.Ticks, m_taskIndex);
}
//-----------------------------------------------------------------------------------
// API that subclasses override to provide task-specific logic.
//
protected abstract void Work();
}
}
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