//****************************************
private void Cancel(KeyedLockInstance instance)
{
// Retrieve the current lock state
while (_Locks.TryGetValue(instance.Key !, out var OldQueue))
{
// Can get no results (or no queue at all) if
// - someone releases while we cancel and Release removes us from the queue
// - we disposed
if (OldQueue.IsEmpty)
{
return;
}
var NewQueue = OldQueue.Remove(instance);
if (ReferenceEquals(OldQueue, NewQueue))
{
return;
}
// Apply the changes to the lock queue
if (_Locks.TryUpdate(instance.Key !, NewQueue, OldQueue))
{
return;
}
// Someone modified the lock queue, probably a new waiter, so retry
}
}
private void Release(TKey key)
{
// Retrieve the current lock state
while (_Locks.TryGetValue(key, out var OldQueue))
{
for (; ;)
{
// If it's empty, there's no waiters or they've all cancelled
if (OldQueue.IsEmpty)
{
// Release the lock
if (((IDictionary <TKey, ImmutableList <KeyedLockInstance> >)_Locks).Remove(new KeyValuePair <TKey, ImmutableList <KeyedLockInstance> >(key, OldQueue)))
{
// If we're disposing and the final held lock, complete disposal
if (_Disposer != null && _Locks.IsEmpty)
{
_Disposer.SwitchToComplete();
}
return;
}
// Someone modified the lock queue, probably a new waiter, so retry
break;
}
// Remove the next waiter from the queue
var NextWaiter = OldQueue[0];
var NewQueue = OldQueue.RemoveAt(0);
// Apply the changes to the lock queue
if (!_Locks.TryUpdate(key, NewQueue, OldQueue))
{
// Someone modified the lock queue, probably a new waiter, so retry
break;
}
// Try to activate the waiter
if (NextWaiter.TrySwitchToCompleted())
{
return;
}
// Waiter has cancelled. Try and pull another off the queue
OldQueue = NewQueue;
}
}
// May get here if we dispose
Debug.Fail("Lock was released but not held");
}