/// <summary>
/// thread safe method which adds the given node to the top of the list
/// </summary>
/// <param name="cachenode">node to be added, if the node is added by some other thread it returns</param>
internal void AddFirst(LinkedListNode <CacheNode <T, V> > cachenode)
{
bool added = false;
int retrycount = 0;
do
{
bool firstlocktaken = false;
bool nextlocktaken = false;
bool curlocktaken = false;
CacheNode <T, V> nextNode = null;
try
{
retrycount++;
firstlocktaken = FirstNode.Value.TryLock();
if (!firstlocktaken)
{
continue;
}
curlocktaken = cachenode.Value.TryLock();
if (!curlocktaken)
{
continue;
}
if (cachenode.List != null)
{
return; //added by another thread
}
if (FirstNode.Next == cachenode)
{
return; //no need for promotion
}
nextNode = FirstNode.Next.Value;
nextlocktaken = nextNode.TryLock();
if (!nextlocktaken)
{
continue;
}
this.list.AddAfter(FirstNode, cachenode);
added = true;
} finally
{
if (nextlocktaken)
{
nextNode.UnlockNode();
}
if (curlocktaken)
{
cachenode.Value.UnlockNode();
}
if (firstlocktaken)
{
FirstNode.Value.UnlockNode();
}
if (retrycount % 100 == 0)
{
Logger.Info($"retryAddFirst {cachenode.Value.key} tries {retrycount}");
}
Thread.Sleep(0);
}
} while (!added);
}