private bool TryDequeue(WorkQueueLocals locals, out IThreadPoolWorkItem callback, out bool missedSteal)
{
var localQueue = locals.Queue;
missedSteal = false;
if ((callback = localQueue.LocalPop()) == null && // first try the local queue
!_queue.TryDequeue(out callback)) // then try the global queue
{
// finally try to steal from another thread's local queue
var queues = Volatile.Read(ref _localQueues);
int c = queues.Length;
int maxIndex = c - 1;
int i = locals.Random.Next(c);
while (c > 0)
{
i = i < maxIndex ? i + 1 : 0;
var otherQueue = queues[i];
if (otherQueue != localQueue && otherQueue.CanSteal)
{
callback = otherQueue.TrySteal(ref missedSteal);
if (callback != null)
{
break;
}
}
c--;
}
}
return(callback != null);
}
public IEnumerable <IThreadPoolWorkItem> GetConsumingEnumerable()
{
using (var locals = new WorkQueueLocals(ref _localQueues))
{
_localQueue = locals.Queue;
while (true)
{
IThreadPoolWorkItem work;
if (TryDequeue(locals, out work, out var missedSteal))
{
yield return(work);
}
else if (IsAddingCompleted)
{
while (TryDequeue(locals, out work, out missedSteal))
{
yield return(work);
}
break;
}
else
{
if (missedSteal)
{
EnsureThreadRequested();
}
_semaphore.Wait();
MarkThreadRequestSatisfied();
}
}
}
}
public void Dispatch(Action <TWorkItem, CancellationToken> action, CancellationToken cancellationToken)
{
using var locals = new WorkQueueLocals(this);
try
{
CustomWorkQueueNonGenericStore.LocalQueue = locals.Queue;
var waitAdded = false;
var spinWait = new SpinWait();
while (!cancellationToken.IsCancellationRequested)
{
if (TryDequeue(locals, out var work, out var missedSteal))
{
if (!waitAdded)
{
SignalOneThread();
}
do
{
action(work, cancellationToken);
} while (TryDequeue(locals, out work, out missedSteal));
}
if (!waitAdded)
{
AddWaitNode(locals.WaitNode, ref spinWait);
waitAdded = true;
continue;
}
if (missedSteal)
{
spinWait.SpinOnce();
continue;
}
locals.Semaphore.Wait(cancellationToken);
spinWait.Reset();
waitAdded = false;
}
cancellationToken.ThrowIfCancellationRequested();
}
finally
{
CustomWorkQueueNonGenericStore.LocalQueue = null;
}
}
public async Task DispatchAsync(Func<TWorkItem, CancellationToken, Task> action, CancellationToken cancellationToken)
{
using var locals = new WorkQueueLocals(this);
try
{
LocalQueue.Value = locals.Queue;
var waitAdded = false;
var spinWait = new SpinWait();
while (!cancellationToken.IsCancellationRequested)
{
if (TryDequeue(locals, out var work, out var missedSteal))
{
if (!waitAdded) SignalOneThread();
do
{
await action(work, cancellationToken);
} while (TryDequeue(locals, out work, out missedSteal));
}
if (!waitAdded)
{
AddWaitNode(locals.WaitNode, ref spinWait);
waitAdded = true;
continue;
}
if (missedSteal)
{
spinWait.SpinOnce();
continue;
}
await locals.Semaphore.WaitAsync(cancellationToken);
spinWait.Reset();
waitAdded = false;
}
cancellationToken.ThrowIfCancellationRequested();
}
finally
{
LocalQueue.Value = null;
}
}
