[Diagnostics] Add EventSource Callback Possible Deadlock Warning

Author: mdh1418

docs/core/diagnostics/eventsource.md

@@ -20,6 +20,17 @@ your own custom events.
 > Many technologies that integrate with EventSource use the terms 'Tracing' and 'Traces' instead of 'Logging' and 'Logs'.
 > The meaning is the same here.
 
+> [!WARNING]
+> Potential Deadlocks with EventSource Callbacks
+>
+> When implementing EventSources, be cautious with invoking lock-acquiring APIs within EventSource callbacks. EventSource instances are initialized early in the runtime, before some core features are fully initialized. As a result, the re-entrant behavior of EventSource callbacks may cause deadlocks if the callback attempts to acquire locks already held by the thread that triggered the callback.
+>
+> To mitigate this risk, consider the following precautions:
+>
+> - **Avoid Complex Operations**: Refrain from performing complex operations within the callback that might acquire additional locks.
+> - **Minimize Lock Duration**: Ensure that any locks acquired within the callback are not held for extended periods.
+> - **Use Non-blocking APIs**: Prefer using non-blocking APIs within the callback to avoid potential deadlocks.
+
 - [Getting started](./eventsource-getting-started.md)
 - [Instrumenting code to create events](./eventsource-instrumentation.md)
 - [Collecting and viewing event traces](./eventsource-collect-and-view-traces.md)