Moved the IM shutdown before setting data model provider to null in the

server shutdown sequence.

Author: jadhavrohit924

src/app/InteractionModelEngine.cpp

@@ -198,8 +198,6 @@ void InteractionModelEngine::Shutdown()
 
     mTimedHandlers.ReleaseAll();
 
-    mReadHandlers.ReleaseAll();
-
 #if CHIP_CONFIG_ENABLE_READ_CLIENT
     // Shut down any subscription clients that are still around.  They won't be
     // able to work after this point anyway, since we're about to drop our refs
@@ -220,6 +218,7 @@ void InteractionModelEngine::Shutdown()
         readClient->mpImEngine = nullptr;
         auto * tmpClient       = readClient->GetNextClient();
         readClient->SetNextClient(nullptr);
+        readClient->Close(CHIP_NO_ERROR);
         readClient = tmpClient;
     }
 
@@ -229,6 +228,7 @@ void InteractionModelEngine::Shutdown()
     mpActiveReadClientList = nullptr;
 #endif // CHIP_CONFIG_ENABLE_READ_CLIENT
 
+    mReadHandlers.ReleaseAll();
     for (auto & writeHandler : mWriteHandlers)
     {
         if (!writeHandler.IsFree())
@@ -1865,15 +1865,15 @@ Protocols::InteractionModel::Status InteractionModelEngine::CheckCommandExistenc
 
 DataModel::Provider * InteractionModelEngine::SetDataModelProvider(DataModel::Provider * model)
 {
-    // Altering data model should not be done while IM is actively handling requests.
-    VerifyOrDie(mReadHandlers.begin() == mReadHandlers.end());
-
     if (model == mDataModelProvider)
     {
         // no-op, just return
         return model;
     }
 
+    // Altering data model should not be done while IM is actively handling requests.
+    VerifyOrDie(mReadHandlers.begin() == mReadHandlers.end());
+
     DataModel::Provider * oldModel = mDataModelProvider;
     if (oldModel != nullptr)
     {

src/app/server/Server.cpp

@@ -652,6 +652,7 @@ void Server::Shutdown()
     app::DnssdServer::Instance().SetICDManager(nullptr);
 #endif // CHIP_CONFIG_ENABLE_ICD_SERVER
 
+    app::InteractionModelEngine::GetInstance()->Shutdown();
     app::InteractionModelEngine::GetInstance()->SetDataModelProvider(nullptr);
     app::DnssdServer::Instance().SetCommissioningModeProvider(nullptr);
     Dnssd::ServiceAdvertiser::Instance().Shutdown();
@@ -670,7 +671,6 @@ void Server::Shutdown()
 #endif // CHIP_DEVICE_CONFIG_ENABLE_COMMISSIONER_DISCOVERY
 
     Dnssd::Resolver::Instance().Shutdown();
-    app::InteractionModelEngine::GetInstance()->Shutdown();
 #if CHIP_CONFIG_ENABLE_ICD_SERVER
     app::InteractionModelEngine::GetInstance()->SetICDManager(nullptr);
 #endif // CHIP_CONFIG_ENABLE_ICD_SERVER