// (yurig): This method has been intentionally split from DispatchLoop()
// result.Block() inside causes Result<DispatchWorkItem> to never be disposed.
// By moving it into its own method we ensure its garbage collection as it is
// popped off the stack. Do NOT inline this method into DispatchLoop().
private bool GetNextWorkItem(out Action callback)
{
if (!_inbox.TryPop(out callback))
{
var result = new Result <DispatchWorkItem>(TimeSpan.MaxValue);
// reset the dispatch queue for this thread
AsyncUtil.CurrentDispatchQueue = null;
_queue = null;
// check if thread is associated with a host already
if (_host == null)
{
// NOTE (steveb): this is a brand new thread without a host yet
// return the thread to the dispatch scheduler
DispatchThreadScheduler.ReleaseThread(this, result);
}
else
{
// request another work-item
_host.RequestWorkItem(this, result);
}
// block until a work item is available
result.Block();
// check if we received a work item or an exception to shutdown
if (result.HasException && (result.Exception is DispatchThreadShutdownException))
{
// time to shut down
_log.DebugFormat("DispatchThread #{0} destroyed", _id);
return(false);
}
callback = result.Value.WorkItem;
_queue = result.Value.DispatchQueue;
// TODO (steveb): handle the weird case where _queue is null
// set the dispatch queue for this thread
AsyncUtil.CurrentDispatchQueue = _queue;
}
return(true);
}
private void DispatchLoop()
{
// set thread-local self-reference
CurrentThread = this;
// begin thread loop
try {
while (true)
{
// check if queue has a work-item
Action callback;
if (!_inbox.TryPop(out callback))
{
var result = new Result <DispatchWorkItem>(TimeSpan.MaxValue);
// reset the dispatch queue for this thread
AsyncUtil.CurrentDispatchQueue = null;
// check if thread is associated with a host already
if (_host == null)
{
// NOTE (steveb): this is a brand new thread without a host yet
// return the thread to the dispatch scheduler
DispatchThreadScheduler.ReleaseThread(this, result);
}
else
{
// request another work-item
_host.RequestWorkItem(this, result);
}
// block until a work item is available
result.Block();
// check if we received a work item or an exception to shutdown
if (result.HasException && (result.Exception is DispatchThreadShutdownException))
{
// time to shut down
_log.DebugFormat("DispatchThread #{0} destroyed", _id);
return;
}
callback = result.Value.WorkItem;
_queue = result.Value.DispatchQueue;
// TODO (steveb): handle the weird case where _queue is null
// set the dispatch queue for this thread
AsyncUtil.CurrentDispatchQueue = _queue;
}
// execute work-item
if (callback != null)
{
try {
callback();
} catch (Exception e) {
_log.Warn("an unhandled exception occurred while executing the work-item", e);
}
}
}
} catch (Exception e) {
// something went wrong that shouldn't have!
_log.ErrorExceptionMethodCall(e, string.Format("DispatchLoop #{0}: FATAL ERROR", _id));
// TODO (steveb): tell _host about untimely exit; post items in queue to host inbox (o/w we lose them)
} finally {
CurrentThread = null;
}
}