internal CancellationTokenRegistration Register(Action callback, bool useSynchronizationContext)
{
CheckDisposed();
var tokenReg = new CancellationTokenRegistration(CustomInterlocked.Increment(ref currId), this);
/* If the source is already canceled we execute the callback immediately
* if not, we try to add it to the queue and if it is currently being processed
* we try to execute it back ourselves to be sure the callback is ran
*/
if (IsCancellationRequested)
{
callback();
}
else
{
callbacks.TryAdd(tokenReg, callback);
if (IsCancellationRequested && callbacks.TryRemove(tokenReg, out callback))
{
callback();
}
}
return(tokenReg);
}
void CommitChangeToHandle(long stamp)
{
CustomInterlocked.Increment(ref used);
var tmpHandle = Handle;
if (tmpHandle != null)
{
// First in all case we carry the operation we were called for
if ((stamp & 1) == 1)
{
tmpHandle.Set();
}
else
{
tmpHandle.Reset();
}
/* Then what may happen is that the two suboperations (state change and handle change)
* overlapped with others. In our case it doesn't matter if the two suboperations aren't
* executed together at the same time, the only thing we have to make sure of is that both
* state and handle are synchronized on the last visible state change.
*
* For instance if S is state change and H is handle change, for 3 concurrent operations
* we may have the following serialized timeline: S1 S2 H2 S3 H3 H1
* Which is perfectly fine (all S were converted to H at some stage) but in that case
* we have a mismatch between S and H at the end because the last operations done were
* S3/H1. We thus need to repeat H3 to get to the desired final state.
*/
int currentState;
do
{
currentState = state;
if (currentState != stamp && (stamp & 1) != (currentState & 1))
{
if ((currentState & 1) == 1)
{
tmpHandle.Set();
}
else
{
tmpHandle.Reset();
}
}
} while (currentState != state);
}
CustomInterlocked.Decrement(ref used);
}