/// <summary>
/// Pause scheduler until all scheduled work items on the given context have completed.
/// </summary>
/// <param name="context">The scheduler context on which to wait.</param>
internal void PauseForQuiescence(SchedulerContext context)
{
if (context.Empty.WaitOne(0) || !this.started || this.completed)
{
return;
}
// Pulse the future queue to process any work items that are either due or
// non-reachable due to having a start time past the finalization time.
this.futureQueuePulse.Set();
if (!this.isSchedulerThread.Value && !this.allowSchedulingOnExternalThreads)
{
// this is not a scheduler thread, so just wait for the context to empty and return
context.Empty.WaitOne();
return;
}
// continue executing work items on this scheduler thread while waiting for the context to empty
while (!this.forcedShutdownRequested && !context.Empty.WaitOne(0))
{
WorkItem wi;
if (this.nextWorkitem.Value != null)
{
// if there is a queued local work item, try to run it first
wi = (WorkItem)this.nextWorkitem.Value;
this.nextWorkitem.Value = null;
this.counters?.Decrement(SchedulerCounters.LocalQueueCount);
if (wi.SyncLock.TryLock())
{
this.counters?.Increment(SchedulerCounters.LocalWorkitemsPerSecond);
goto ExecuteWorkItem;
}
else
{
// it's locked, so let someone else have it
this.Schedule(wi, false);
this.counters?.Increment(SchedulerCounters.LocalToGlobalPromotions);
}
}
// try to get another item from the global queue
if (!this.globalWorkitems.TryDequeue(out wi))
{
// no work left
continue;
}
this.counters?.Increment(SchedulerCounters.GlobalWorkitemsPerSecond);
ExecuteWorkItem:
this.currentWorkitemTime.Value = wi.StartTime;
this.ExecuteAndRelease(wi.SyncLock, wi.Callback, wi.SchedulerContext);
}
}
private void ExecuteAndRelease(SynchronizationLock synchronizationObject, Action action, SchedulerContext context)
{
try
{
action();
this.counters?.Increment(SchedulerCounters.WorkitemsPerSecond);
}
catch (Exception e) when(this.errorHandler(e))
{
}
finally
{
synchronizationObject.Release();
context.Exit();
}
}
/// <summary>
/// Stops scheduling further work items on the given context.
/// </summary>
/// <param name="context">The context on which scheduling should cease.</param>
public void StopScheduling(SchedulerContext context)
{
// wait for already scheduled work to finish
this.PauseForQuiescence(context);
context.Stop();
}
/// <summary>
/// Starts scheduling work on the given context.
/// </summary>
/// <param name="context">The context on which scheduling should start.</param>
public void StartScheduling(SchedulerContext context)
{
context.Start(this.Clock);
}
/// <summary>
/// Enqueues a workitem and, if possible, kicks off a worker thread to pick it up.
/// </summary>
/// <param name="synchronizationObject">Synchronization object.</param>
/// <param name="action">Action to execute.</param>
/// <param name="startTime">Scheduled start time.</param>
/// <param name="context">The scheduler context on which to schedule the action.</param>
/// <param name="asContinuation">Flag whether to execute once current operation completes.</param>
/// <param name="allowSchedulingPastFinalization">Allow scheduling past finalization time.</param>
public void Schedule(SynchronizationLock synchronizationObject, Action action, DateTime startTime, SchedulerContext context, bool asContinuation = true, bool allowSchedulingPastFinalization = false)
{
if (synchronizationObject == null || action == null || context == null)
{
throw new ArgumentNullException();
}
if (!allowSchedulingPastFinalization && startTime > context.FinalizeTime)
{
return;
}
// Enter the context to track this new work item. The context will be exited
// only after the work item has been successfully executed (or dropped).
context.Enter();
this.Schedule(new WorkItem()
{
SyncLock = synchronizationObject, Callback = action, StartTime = startTime, SchedulerContext = context
}, asContinuation);
}
/// <summary>
/// Attempts to execute the delegate immediately, on the calling thread, without scheduling.
/// </summary>
/// <param name="synchronizationObject">Synchronization object.</param>
/// <param name="action">Action to execute.</param>
/// <param name="startTime">Scheduled start time.</param>
/// <param name="context">The scheduler context on which to execute the action.</param>
/// <returns>Success flag.</returns>
public bool TryExecute(SynchronizationLock synchronizationObject, Action action, DateTime startTime, SchedulerContext context)
{
if (this.forcedShutdownRequested || startTime > context.FinalizeTime)
{
return(true);
}
if (startTime > this.clock.GetCurrentTime() && this.delayFutureWorkitemsUntilDue)
{
return(false);
}
if (!this.isSchedulerThread.Value && !this.allowSchedulingOnExternalThreads)
{
// this thread is not ours, so return
return(false);
}
// try to acquire a lock
// however, if this thread already has the lock, we have to give up to keep the no-reentrancy guarantee
if (!synchronizationObject.TryLock())
{
return(false);
}
// ExecuteAndRelease assumes that the context has already been entered, so we must explicitly
// enter it here. The context will be exited just prior to returning from ExecuteAndRelease.
context.Enter();
this.ExecuteAndRelease(synchronizationObject, action, context);
this.counters?.Increment(SchedulerCounters.ImmediateWorkitemsPerSecond);
return(true);
}
/// <summary>
/// Attempts to execute the delegate immediately, on the calling thread, without scheduling.
/// </summary>
/// <typeparam name="T">Action argument type.</typeparam>
/// <param name="synchronizationObject">Synchronization object.</param>
/// <param name="action">Action to execute.</param>
/// <param name="argument">Action argument.</param>
/// <param name="startTime">Scheduled start time.</param>
/// <param name="context">The scheduler context on which to execute the action.</param>
/// <param name="outputActionTiming">Indicates whether to output action timing information.</param>
/// <param name="actionStartTime">The time the runtime started executing the action.</param>
/// <param name="actionEndTime">The time the runtime ended executing the action.</param>
/// <returns>Success flag.</returns>
public bool TryExecute <T>(
SynchronizationLock synchronizationObject,
Action <T> action,
T argument,
DateTime startTime,
SchedulerContext context,
bool outputActionTiming,
out DateTime actionStartTime,
out DateTime actionEndTime)
{
actionStartTime = DateTime.MinValue;
actionEndTime = DateTime.MinValue;
if (this.forcedShutdownRequested || startTime > context.FinalizeTime)
{
actionStartTime = actionEndTime = this.clock.GetCurrentTime();
return(true);
}
if (startTime > this.clock.GetCurrentTime() && this.delayFutureWorkitemsUntilDue)
{
return(false);
}
if (!this.isSchedulerThread.Value && !this.allowSchedulingOnExternalThreads)
{
// this thread is not ours, so return
return(false);
}
// try to acquire a lock on the sync context
// however, if this thread already has the lock, we have to give up to keep the no-reentrancy guarantee
if (!synchronizationObject.TryLock())
{
return(false);
}
try
{
// Unlike ExecuteAndRelease, which assumes that the context has already been entered (e.g.
// when the work item was first created), we need to explicitly enter the context prior to
// running the action. The context will be exited in the finally clause.
context.Enter();
this.counters?.Increment(SchedulerCounters.WorkitemsPerSecond);
this.counters?.Increment(SchedulerCounters.ImmediateWorkitemsPerSecond);
if (outputActionTiming)
{
actionStartTime = this.clock.GetCurrentTime();
}
action(argument);
}
catch (Exception e) when(this.errorHandler(e))
{
}
finally
{
if (outputActionTiming)
{
actionEndTime = this.clock.GetCurrentTime();
}
synchronizationObject.Release();
context.Exit();
}
return(true);
}
