private static void WaitOnReadset(Transaction me, ReadSet readSet, int readstamp)
{
#if DEBUG
Console.WriteLine("ENTERED WAIT ON RETRY: " + me.ID);
#endif
if (readSet.Count == 0)
{
throw new STMInvalidRetryException();
}
var waiton = new WaitHandle[readSet.Count()];
var i = 0;
foreach (var item in readSet)
{
waiton[i] = item.Key.RegisterWaitHandle();
i++;
}
if (!readSet.Validate(me, readstamp))
{
return;
}
#if DEBUG
Console.WriteLine("WAIT ON RETRY: " + me.ID);
#endif
WaitHandle.WaitAny(waiton);
#if DEBUG
Console.WriteLine("WAIT ON RETRY: " + me.ID);
#endif
}
public void Merge(ReadSet other)
{
foreach (var kvpair in other)
{
if (!_lockObjects.ContainsKey(kvpair.Key))
{
_lockObjects[kvpair.Key] = kvpair.Value;
}
}
}
private static T AtomicInternal <T>(IList <Func <T> > stmActions)
{
Debug.Assert(stmActions.Count > 0);
var result = default(T);
var index = 0;
var overAllReadSet = new ReadSet();
var ovarAllReadstamp = -1;
var nrAttempts = 0;
while (true)
{
var stmAction = stmActions[index];
//Start new or nested transaction
var prevTransaction = Transaction.LocalTransaction;
var me = prevTransaction.Status == TransactionStatus.Active ?
Transaction.StartNestedTransaction(prevTransaction) :
Transaction.StartTransaction();
if (index == 0)
{
ovarAllReadstamp = me.ReadStamp;
}
try
{
//Execute transaction body
result = stmAction();
if (me.Commit())
{
return(result);
}
}
catch (STMAbortException)
{
//Skips straight to abort a reexecute
}
catch (STMRetryException)
{
index = HandleRetry(stmActions, me, index, overAllReadSet, ovarAllReadstamp);
}
catch (Exception) //Catch non stm related exceptions which occurs in transactions
{
//Throw exception of transaction can commit
//Else abort and rerun transaction
if (me.Commit())
{
throw;
}
}
nrAttempts++;
me.Abort();
//If the transaction is nested restore the parent as current transaction before retrying
if (me.IsNested)
{
Transaction.LocalTransaction = me.Parent;
}
if (nrAttempts == MAX_ATTEMPTS)
{
throw new STMMaxAttemptException("Fatal error: max attempts reached");
}
}
}
private static void WaitOnReadset(Transaction me, ReadSet readSet)
{
WaitOnReadset(me, readSet, me.ReadStamp);
}
private static int HandleRetry <T>(IList <Func <T> > stmActions, Transaction me, int index, ReadSet overAllReadSet, int originalReadstamp)
{
if (stmActions.Count == 1) //Optimized for when there are no orelse blocks
{
WaitOnReadset(me, me.ReadSet);
}
else if (stmActions.Count == index + 1) //Final orelse block
{
overAllReadSet.Merge(me.ReadSet);
WaitOnReadset(me, overAllReadSet, originalReadstamp);
index = 0;
}
else //Non final atomic or orelse blocks
{
#if DEBUG
Console.WriteLine("Transaction: " + me.ID + " ORELSE jump");
#endif
overAllReadSet.Merge(me.ReadSet);
index++;
}
return(index);
}
