[None][fix] Add lock for request_to_session in sendReadySingal (NVIDIA#8310)

Signed-off-by: Chuang Zhu <[email protected]>

Author: chuangz0

cpp/tensorrt_llm/batch_manager/dataTransceiver.cpp

@@ -401,10 +401,14 @@ class CacheSender::Impl
 
     void sendReadySignal(LlmRequest::RequestIdType requestId, bool isReady)
     {
-        auto it = mRequestToSession.find(requestId);
-        TLLM_CHECK(it != mRequestToSession.end());
-        auto& session = it->second;
-        auto const& connections = session.getConnections();
+        TransferSession* session = nullptr;
+        {
+            std::unique_lock<std::mutex> lock(mMtxForMap);
+            auto it = mRequestToSession.find(requestId);
+            TLLM_CHECK(it != mRequestToSession.end());
+            session = std::addressof(it->second);
+        }
+        auto const& connections = session->getConnections();
         for (size_t i = 0; i < connections.size(); i++)
         {
             auto* agentConnectionManager = dynamic_cast<executor::kv_cache::AgentConnectionManager*>(mManager);