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Fix deadlock in EventPipeEventDispatcher #92806

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merged 1 commit into from
Oct 2, 2023
Merged

Fix deadlock in EventPipeEventDispatcher #92806

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31 changes: 20 additions & 11 deletions ...braries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventPipeEventDispatcher.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -103,8 +103,8 @@ private void CommitDispatchConfiguration()
new EventPipeProviderConfiguration(NativeRuntimeEventSource.EventSourceName, (ulong)aggregatedKeywords, (uint)enableLevel, null)
};

m_sessionID = EventPipeInternal.Enable(null, EventPipeSerializationFormat.NetTrace, DefaultEventListenerCircularMBSize, providerConfiguration);
if (m_sessionID == 0)
ulong sessionID = EventPipeInternal.Enable(null, EventPipeSerializationFormat.NetTrace, DefaultEventListenerCircularMBSize, providerConfiguration);
if (sessionID == 0)
{
throw new EventSourceException(SR.EventSource_CouldNotEnableEventPipe);
}
Expand All @@ -113,7 +113,7 @@ private void CommitDispatchConfiguration()
EventPipeSessionInfo sessionInfo;
unsafe
{
if (!EventPipeInternal.GetSessionInfo(m_sessionID, &sessionInfo))
if (!EventPipeInternal.GetSessionInfo(sessionID, &sessionInfo))
{
Debug.Fail("GetSessionInfo returned false.");
}
Expand All @@ -124,8 +124,11 @@ private void CommitDispatchConfiguration()
long syncTimeQPC = sessionInfo.StartTimeStamp;
long timeQPCFrequency = sessionInfo.TimeStampFrequency;

Debug.Assert(Volatile.Read(ref m_sessionID) == 0);
Volatile.Write(ref m_sessionID, sessionID);

// Start the dispatch task.
StartDispatchTask(m_sessionID, syncTimeUtc, syncTimeQPC, timeQPCFrequency);
StartDispatchTask(sessionID, syncTimeUtc, syncTimeQPC, timeQPCFrequency);
}

private void StartDispatchTask(ulong sessionID, DateTime syncTimeUtc, long syncTimeQPC, long timeQPCFrequency)
Expand All @@ -147,10 +150,11 @@ private void SetStopDispatchTask()
return;
}

Debug.Assert(m_sessionID != 0);
ulong sessionID = Volatile.Read(ref m_sessionID);
Debug.Assert(sessionID != 0);
m_dispatchTaskCancellationSource.Cancel();
EventPipeInternal.SignalSession(m_sessionID);
m_sessionID = 0;
EventPipeInternal.SignalSession(sessionID);
Volatile.Write(ref m_sessionID, 0);
}

private unsafe void DispatchEventsToEventListeners(ulong sessionID, DateTime syncTimeUtc, long syncTimeQPC, long timeQPCFrequency, Task? previousDispatchTask, CancellationToken token)
Expand Down Expand Up @@ -190,12 +194,17 @@ private unsafe void DispatchEventsToEventListeners(ulong sessionID, DateTime syn
}
}

lock (m_dispatchControlLock)
// Wait for SignalSession() to be called before we call disable, otherwise
// the SignalSession() call could be on a disabled session.
SpinWait sw = default;
while (Volatile.Read(ref m_sessionID) == sessionID)
{
// Disable the old session. This can happen asynchronously since we aren't using the old session
// anymore. We take the lock to make sure we don't call SignalSession on an invalid session ID.
EventPipeInternal.Disable(sessionID);
sw.SpinOnce();
}

// Disable the old session. This can happen asynchronously since we aren't using the old session
// anymore.
EventPipeInternal.Disable(sessionID);
}

/// <summary>
Expand Down