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ThreadPoolScheduler.cs
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ThreadPoolScheduler.cs
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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
#if !WINDOWS && !NO_THREAD
using System.Collections.Generic;
using System.Reactive.Disposables;
using System.Threading;
namespace System.Reactive.Concurrency
{
/// <summary>
/// Represents an object that schedules units of work on the CLR thread pool.
/// </summary>
/// <seealso cref="ThreadPoolScheduler.Instance">Singleton instance of this type exposed through this static property.</seealso>
public sealed class ThreadPoolScheduler : LocalScheduler, ISchedulerLongRunning, ISchedulerPeriodic
{
private static readonly ThreadPoolScheduler s_instance = new ThreadPoolScheduler();
private static readonly NewThreadScheduler s_newBackgroundThread = new NewThreadScheduler(action => new Thread(action) { IsBackground = true });
/// <summary>
/// Gets the singleton instance of the CLR thread pool scheduler.
/// </summary>
public static ThreadPoolScheduler Instance
{
get
{
return s_instance;
}
}
ThreadPoolScheduler()
{
}
/// <summary>
/// Schedules an action to be executed.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">State passed to the action to be executed.</param>
/// <param name="action">Action to be executed.</param>
/// <returns>The disposable object used to cancel the scheduled action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
public override IDisposable Schedule<TState>(TState state, Func<IScheduler, TState, IDisposable> action)
{
if (action == null)
throw new ArgumentNullException("action");
var d = new SingleAssignmentDisposable();
ThreadPool.QueueUserWorkItem(_ =>
{
if (!d.IsDisposed)
d.Disposable = action(this, state);
}, null);
return d;
}
/// <summary>
/// Schedules an action to be executed after dueTime, using a System.Threading.Timer object.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">State passed to the action to be executed.</param>
/// <param name="action">Action to be executed.</param>
/// <param name="dueTime">Relative time after which to execute the action.</param>
/// <returns>The disposable object used to cancel the scheduled action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
public override IDisposable Schedule<TState>(TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)
{
if (action == null)
throw new ArgumentNullException("action");
var dt = Scheduler.Normalize(dueTime);
if (dt.Ticks == 0)
return Schedule(state, action);
return new Timer<TState>(this, state, dt, action);
}
/// <summary>
/// Schedules a long-running task by creating a new thread. Cancellation happens through polling.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">State passed to the action to be executed.</param>
/// <param name="action">Action to be executed.</param>
/// <returns>The disposable object used to cancel the scheduled action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
public IDisposable ScheduleLongRunning<TState>(TState state, Action<TState, ICancelable> action)
{
if (action == null)
throw new ArgumentNullException("action");
return s_newBackgroundThread.ScheduleLongRunning(state, action);
}
#if !NO_STOPWATCH
/// <summary>
/// Starts a new stopwatch object.
/// </summary>
/// <returns>New stopwatch object; started at the time of the request.</returns>
public override IStopwatch StartStopwatch()
{
//
// Strictly speaking, this explicit override is not necessary because the base implementation calls into
// the enlightenment module to obtain the CAL, which would circle back to System.Reactive.PlatformServices
// where we're currently running. This is merely a short-circuit to avoid the additional roundtrip.
//
return new StopwatchImpl();
}
#endif
/// <summary>
/// Schedules a periodic piece of work, using a System.Threading.Timer object.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">Initial state passed to the action upon the first iteration.</param>
/// <param name="period">Period for running the work periodically.</param>
/// <param name="action">Action to be executed, potentially updating the state.</param>
/// <returns>The disposable object used to cancel the scheduled recurring action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="period"/> is less than or equal to zero.</exception>
public IDisposable SchedulePeriodic<TState>(TState state, TimeSpan period, Func<TState, TState> action)
{
//
// MSDN documentation states the following:
//
// "If period is zero (0) or negative one (-1) milliseconds and dueTime is positive, callback is invoked once;
// the periodic behavior of the timer is disabled, but can be re-enabled using the Change method."
//
if (period <= TimeSpan.Zero)
throw new ArgumentOutOfRangeException("period");
if (action == null)
throw new ArgumentNullException("action");
return new PeriodicTimer<TState>(state, period, action);
}
#if USE_TIMER_SELF_ROOT
//
// See ConcurrencyAbstractionLayerImpl.cs for more information about the code
// below and its timer rooting behavior.
//
sealed class Timer<TState> : IDisposable
{
private readonly MultipleAssignmentDisposable _disposable;
private readonly IScheduler _parent;
private readonly TState _state;
private Func<IScheduler, TState, IDisposable> _action;
private volatile System.Threading.Timer _timer;
public Timer(IScheduler parent, TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)
{
_parent = parent;
_state = state;
_action = action;
_disposable = new MultipleAssignmentDisposable();
_disposable.Disposable = Disposable.Create(Stop);
// Don't want the spin wait in Tick to get stuck if this thread gets aborted.
try { }
finally
{
//
// Rooting of the timer happens through the this.Tick delegate's target object,
// which is the current instance and has a field to store the Timer instance.
//
_timer = new System.Threading.Timer(this.Tick, null, dueTime, TimeSpan.FromMilliseconds(System.Threading.Timeout.Infinite));
}
}
private void Tick(object state)
{
try
{
_disposable.Disposable = _action(_parent, _state);
}
finally
{
SpinWait.SpinUntil(IsTimerAssigned);
Stop();
}
}
private bool IsTimerAssigned()
{
return _timer != null;
}
public void Dispose()
{
_disposable.Dispose();
}
private void Stop()
{
var timer = _timer;
if (timer != TimerStubs.Never)
{
_action = Nop;
_timer = TimerStubs.Never;
timer.Dispose();
}
}
private IDisposable Nop(IScheduler scheduler, TState state)
{
return Disposable.Empty;
}
}
sealed class PeriodicTimer<TState> : IDisposable
{
private TState _state;
private Func<TState, TState> _action;
private readonly AsyncLock _gate;
private volatile System.Threading.Timer _timer;
public PeriodicTimer(TState state, TimeSpan period, Func<TState, TState> action)
{
_state = state;
_action = action;
_gate = new AsyncLock();
//
// Rooting of the timer happens through the this.Tick delegate's target object,
// which is the current instance and has a field to store the Timer instance.
//
_timer = new System.Threading.Timer(this.Tick, null, period, period);
}
private void Tick(object state)
{
_gate.Wait(() =>
{
_state = _action(_state);
});
}
public void Dispose()
{
var timer = _timer;
if (timer != null)
{
_action = Stubs<TState>.I;
_timer = null;
timer.Dispose();
_gate.Dispose();
}
}
}
#else
abstract class Timer
{
//
// Note: the dictionary exists to "root" the timers so that they are not garbage collected and finalized while they are running.
//
#if !NO_HASHSET
protected static readonly HashSet<System.Threading.Timer> s_timers = new HashSet<System.Threading.Timer>();
#else
protected static readonly Dictionary<System.Threading.Timer, object> s_timers = new Dictionary<System.Threading.Timer, object>();
#endif
}
sealed class Timer<TState> : Timer, IDisposable
{
private readonly MultipleAssignmentDisposable _disposable;
private readonly IScheduler _parent;
private readonly TState _state;
private Func<IScheduler, TState, IDisposable> _action;
private System.Threading.Timer _timer;
private bool _hasAdded;
private bool _hasRemoved;
public Timer(IScheduler parent, TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)
{
_disposable = new MultipleAssignmentDisposable();
_disposable.Disposable = Disposable.Create(Unroot);
_parent = parent;
_state = state;
_action = action;
_timer = new System.Threading.Timer(Tick, null, dueTime, TimeSpan.FromMilliseconds(System.Threading.Timeout.Infinite));
lock (s_timers)
{
if (!_hasRemoved)
{
#if !NO_HASHSET
s_timers.Add(_timer);
#else
s_timers.Add(_timer, null);
#endif
_hasAdded = true;
}
}
}
private void Tick(object state)
{
try
{
_disposable.Disposable = _action(_parent, _state);
}
finally
{
Unroot();
}
}
private void Unroot()
{
_action = Nop;
var timer = default(System.Threading.Timer);
lock (s_timers)
{
if (!_hasRemoved)
{
timer = _timer;
_timer = null;
if (_hasAdded && timer != null)
s_timers.Remove(timer);
_hasRemoved = true;
}
}
if (timer != null)
timer.Dispose();
}
private IDisposable Nop(IScheduler scheduler, TState state)
{
return Disposable.Empty;
}
public void Dispose()
{
_disposable.Dispose();
}
}
abstract class PeriodicTimer
{
//
// Note: the dictionary exists to "root" the timers so that they are not garbage collected and finalized while they are running.
//
#if !NO_HASHSET
protected static readonly HashSet<System.Threading.Timer> s_timers = new HashSet<System.Threading.Timer>();
#else
protected static readonly Dictionary<System.Threading.Timer, object> s_timers = new Dictionary<System.Threading.Timer, object>();
#endif
}
sealed class PeriodicTimer<TState> : PeriodicTimer, IDisposable
{
private readonly AsyncLock _gate;
private TState _state;
private Func<TState, TState> _action;
private System.Threading.Timer _timer;
public PeriodicTimer(TState state, TimeSpan period, Func<TState, TState> action)
{
_gate = new AsyncLock();
_state = state;
_action = action;
_timer = new System.Threading.Timer(Tick, null, period, period);
lock (s_timers)
{
#if !NO_HASHSET
s_timers.Add(_timer);
#else
s_timers.Add(_timer, null);
#endif
}
}
private void Tick(object state)
{
_gate.Wait(() =>
{
_state = _action(_state);
});
}
public void Dispose()
{
var timer = default(System.Threading.Timer);
lock (s_timers)
{
timer = _timer;
_timer = null;
if (timer != null)
s_timers.Remove(timer);
}
if (timer != null)
{
timer.Dispose();
_gate.Dispose();
_action = Stubs<TState>.I;
}
}
}
#endif
}
}
#endif