public void Unlock(TransactionHead transaction, bool unlockAll)
{
// All page locking is done by the root of the transaction heirachy. Locks are
// only released when the outermost transaction completes
transaction = transaction.Root;
if (transaction != _lockingTransaction)
{
throw new FileLayerException("You cannot unlock a page that you do not have locked");
}
if (unlockAll)
{
_lockCount = 0;
}
else
{
_lockCount--;
}
if (_lockCount == 0)
{
_lockingTransaction = null;
_unlockEvent.Set();
}
}
public TransactionHead BeginTransaction(ITransaction transaction)
{
TransactionHead parentHead = null;
if (transaction.ParentTransactionId.HasValue)
{
lock (_transactions)
{
if (!_transactions.TryGetValue(transaction.ParentTransactionId.Value, out parentHead))
{
throw new FileLayerException("You can not start a child transaction when the parent transaction is not active");
}
}
}
var transactionHead = new TransactionHead(transaction, parentHead, _pagePool);
lock (_transactions) _transactions.Add(transaction.TransactionId, transactionHead);
return(transactionHead);
}
public void Lock(TransactionHead transaction)
{
// All page locking is done by the root of the transaction heirachy. Locks are
// only released when the outermost transaction completes
transaction = transaction.Root;
// TODO: If there are transactions with modified versions of this
// page then we should wait for these transactions to complete
// and prevent any new write operations to the page
while (true)
{
lock (Versions)
{
if (_unlockEvent == null)
{
_unlockEvent = new ManualResetEventSlim(false);
}
if (_lockingTransaction == null)
{
_lockingTransaction = transaction;
_lockCount = 1;
_unlockEvent.Reset();
return;
}
else if (_lockingTransaction == transaction)
{
_lockCount++;
return;
}
}
_unlockEvent.Wait();
}
}
public TransactionHead(ITransaction transaction, TransactionHead parent, IPagePool pagePool)
{
_pagePool = pagePool;
Transaction = transaction;
Parent = parent;
}
/// <summary>
/// Decrements the count of active transactions
/// </summary>
public bool TransactionEnded(TransactionHead transaction)
{
return(Interlocked.Decrement(ref _transactionCount) == 0);
}
/// <summary>
/// Increments the count of active transactions
/// </summary>
public void TransactionStarted(TransactionHead transaction)
{
Interlocked.Increment(ref _transactionCount);
}
