/// <summary>
/// Used to test if two operations are dependent.
/// However, it is not perfect and it assumes we are only checking
/// co-enabled operations from the same scheduling point.
/// Thus, the following will always appear to be independent,
/// even though this is not always the case:
/// Create and Start, Send and Receive.
/// </summary>
public static bool IsDependent(TidEntry a, TidEntry b)
{
// This method will not detect the dependency between
// Create and Start (because Create's target id is always -1),
// but this is probably fine because we will never be checking that;
// we only check enabled ops against other enabled ops.
// Similarly, we assume that Send and Receive will always be independent
// because the Send would need to enable the Receive to be dependent.
// Receives are independent as they will always be from different threads,
// but they should always have different target ids anyway.
if (
a.TargetId != b.TargetId ||
a.TargetType != b.TargetType ||
a.TargetId == -1 ||
b.TargetId == -1)
{
return(false);
}
// Same target:
if (a.TargetType == OperationTargetType.Inbox)
{
return(a.OpType == OperationType.Send && b.OpType == OperationType.Send);
}
return(true);
}
/// <summary>
/// Update the sleep sets for the top operation on the stack.
/// This will look at the second from top element in the stack
/// and copy forward the sleep set, excluding threads that are dependent
/// with the executed operation.
/// </summary>
/// <param name="stack">Stack</param>
/// <param name="contract">IContract</param>
public static void UpdateSleepSets(Stack stack, IContract contract)
{
if (stack.GetNumSteps() <= 1)
{
return;
}
TidEntryList prevTop = stack.GetSecondFromTop();
TidEntry prevSelected = prevTop.List[prevTop.GetSelected(contract)];
TidEntryList currTop = stack.GetTop();
// For each thread on the top of stack (except previously selected thread and new threads):
// if thread was slept previously
// and thread's op was independent with selected op then:
// the thread is still slept.
// else: not slept.
for (int i = 0; i < prevTop.List.Count; i++)
{
if (i == prevSelected.Id)
{
continue;
}
if (prevTop.List[i].Sleep && !IsDependent(prevTop.List[i], prevSelected))
{
currTop.List[i].Sleep = true;
}
}
}
