/// <summary>Creates a textual description of the deadlock.</summary>
/// <param name="currentChain">The deadlock cycle.</param>
/// <param name="locksHeldByThreads">The table containing what locks are held by each thread holding locks.</param>
/// <returns>The description of the deadlock.</returns>
private static string CreateDeadlockDescription(
CycleComponentNode currentChain,
Dictionary <Thread, List <MonitorState> > locksHeldByThreads)
{
StringBuilder desc = new StringBuilder();
for (CycleComponentNode node = currentChain; node != null; node = node.Next)
{
desc.AppendFormat("Thread {0} waiting on {1} ({2:X}) while holding ",
node.Thread.ManagedThreadId, node.MonitorState.MonitorObject.ToString(),
RuntimeHelpers.GetHashCode(node.MonitorState.MonitorObject));
bool needsComma = false;
foreach (MonitorState ms in locksHeldByThreads[node.Thread])
{
if (needsComma)
{
desc.Append(", ");
}
desc.AppendFormat("{0} ({1:X})", ms.MonitorObject.ToString(),
RuntimeHelpers.GetHashCode(ms.MonitorObject));
needsComma = true;
}
desc.AppendLine();
}
return(desc.ToString());
}
public bool ContainsThread(Thread t)
{
for (CycleComponentNode node = this; node != null; node = node.Next)
{
if (node.Thread == t)
{
return(true);
}
}
return(false);
}
/// <summary>Creates a textual description of the deadlock.</summary>
/// <param name="currentChain">The deadlock cycle.</param>
/// <param name="locksHeldByThreads">The table containing what locks are held by each thread holding locks.</param>
/// <returns>The description of the deadlock.</returns>
private static string CreateDeadlockDescription(
MonitorState competedState,
CycleComponentNode currentChain,
Dictionary <Thread, List <MonitorState> > locksHeldByThreads)
{
StringBuilder desc = new StringBuilder();
for (CycleComponentNode node = currentChain; node != null; node = node.Next)
{
desc.AppendFormat("\r\nThread {0} waiting on: {1} ({2:X})\r\nCalling from:\r\n{3}\nwhile holding:\r\n",
node.Thread.ManagedThreadId, node.MonitorState.MonitorObject.ToString(),
RuntimeHelpers.GetHashCode(node.MonitorState.MonitorObject),
node.MonitorState.traces[node.Thread]);
foreach (MonitorState ms in locksHeldByThreads[node.Thread])
{
desc.AppendFormat("{0} ({1:X})\r\n{2}", ms.MonitorObject.ToString(),
RuntimeHelpers.GetHashCode(ms.MonitorObject), ms.traces[node.Thread]);
}
desc.AppendLine();
}
return(desc.ToString());
}
public CycleComponentNode(Thread thread, MonitorState ms, CycleComponentNode next)
{
Thread = thread;
MonitorState = ms;
Next = next;
}
/// <summary>Creates a textual description of the deadlock.</summary>
/// <param name="currentChain">The deadlock cycle.</param>
/// <param name="locksHeldByThreads">The table containing what locks are held by each thread holding locks.</param>
/// <returns>The description of the deadlock.</returns>
private static string CreateDeadlockDescription(
MonitorState competedState,
CycleComponentNode currentChain,
Dictionary<Thread, List<MonitorState>> locksHeldByThreads)
{
StringBuilder desc = new StringBuilder();
for (CycleComponentNode node = currentChain; node != null; node = node.Next)
{
desc.AppendFormat("\r\nThread {0} waiting on: {1} ({2:X})\r\nCalling from:\r\n{3}\nwhile holding:\r\n",
node.Thread.ManagedThreadId, node.MonitorState.MonitorObject.ToString(),
RuntimeHelpers.GetHashCode(node.MonitorState.MonitorObject),
node.MonitorState.traces[node.Thread]);
foreach (MonitorState ms in locksHeldByThreads[node.Thread])
desc.AppendFormat("{0} ({1:X})\r\n{2}", ms.MonitorObject.ToString(),
RuntimeHelpers.GetHashCode(ms.MonitorObject), ms.traces[node.Thread]);
desc.AppendLine();
}
return desc.ToString();
}
/// <summary>Creates a textual description of the deadlock.</summary>
/// <param name="currentChain">The deadlock cycle.</param>
/// <param name="locksHeldByThreads">The table containing what locks are held by each thread holding locks.</param>
/// <returns>The description of the deadlock.</returns>
private static string CreateDeadlockDescription(
CycleComponentNode currentChain,
Dictionary<Thread, List<MonitorState>> locksHeldByThreads)
{
StringBuilder desc = new StringBuilder();
for (CycleComponentNode node = currentChain; node != null; node = node.Next)
{
desc.AppendFormat("Thread {0} waiting on {1} ({2:X}) while holding ",
node.Thread.ManagedThreadId, node.MonitorState.MonitorObject.ToString(),
RuntimeHelpers.GetHashCode(node.MonitorState.MonitorObject));
bool needsComma = false;
foreach (MonitorState ms in locksHeldByThreads[node.Thread])
{
if (needsComma) desc.Append(", ");
desc.AppendFormat("{0} ({1:X})", ms.MonitorObject.ToString(),
RuntimeHelpers.GetHashCode(ms.MonitorObject));
needsComma = true;
}
desc.AppendLine();
}
return desc.ToString();
}
public CycleComponentNode(Thread thread, MonitorState ms, CycleComponentNode next)
{
Thread = thread;
MonitorState = ms;
Next = next;
}
/// <summary>Throws an exception if a deadlock would be caused by the current thread waiting on the specified lock.</summary>
/// <param name="targetMs">The target lock data.</param>
private static void ThrowIfDeadlockDetected(MonitorState targetMs)
{
// If no thread is holding the target lock, then this won't deadlock...
if (targetMs.OwningThread == null)
{
return;
}
// For the deadlock detection algorithm, we need to know what locks are
// currently held by which threads as well as which threads are waiting on
// which locks. We already have this information, but we need it in a tabular
// form for easier use and better perf.
Dictionary <Thread, List <MonitorState> > locksHeldByThreads;
Dictionary <MonitorState, List <Thread> > threadsWaitingOnLocks;
CreateThreadAndLockTables(out locksHeldByThreads, out threadsWaitingOnLocks);
// As we iterate over the wait graph, we'll need to store the list of threads still left to examine
Queue <CycleComponentNode> threadsToFollow = new Queue <CycleComponentNode>(locksHeldByThreads.Count);
// But rather than just storing the thread, we also store the threads in the cycle that got us to this thread.
// The top of the stack is the actual thread to be examined.
threadsToFollow.Enqueue(new CycleComponentNode(Thread.CurrentThread, targetMs, null));
while (threadsToFollow.Count > 0)
{
// Get the next thread to examine
CycleComponentNode currentChain = threadsToFollow.Dequeue();
Thread currentThread = currentChain.Thread;
// If this thread doesn't hold any locks, no point in examining it
List <MonitorState> locksHeldByThread;
if (!locksHeldByThreads.TryGetValue(currentThread, out locksHeldByThread))
{
continue;
}
// For each lock it does hold, add to the thread examination list all threads
// waiting on it. And for each, see if it completes a cycle that results in
// a deadlock.
foreach (MonitorState ms in locksHeldByThread)
{
List <Thread> nextThreads;
if (!threadsWaitingOnLocks.TryGetValue(ms, out nextThreads))
{
continue;
}
foreach (Thread nextThread in nextThreads)
{
// If any thread waiting on this lock is in the current stack,
// it's completng a cycle... deadlock!
if (currentChain.ContainsThread(nextThread))
{
throw new SynchronizationLockException(
CreateDeadlockDescription(targetMs, currentChain, locksHeldByThreads));
}
// Clone the stack of threads in the possible cycle and add this to the top,
// then queue the stack for examination.
threadsToFollow.Enqueue(new CycleComponentNode(nextThread, ms, currentChain));
}
}
}
}
