[ESP32] Fix the threading issue in nimble (project-chip#29180)

* [ESP32] Fix the threading issue in nimble

Send ble connection error than executing in nimble thread context

* comment explaining why we are posting connection error event

* Adding a comment for kCHIPoBLEConnectionError

src/include/platform/CHIPDeviceEvent.h

@@ -258,6 +258,12 @@ enum InternalEventTypes
     kCHIPoBLEUnsubscribe,
     kCHIPoBLEWriteReceived,
     kCHIPoBLEIndicateConfirm,
+
+    /**
+     * Post this event in case of a BLE connection error. This event should be posted
+     * if the BLE central disconnects without unsubscribing from the BLE characteristic.
+     * This event should populate CHIPoBLEConnectionError structure.
+     */
     kCHIPoBLEConnectionError,
     kCHIPoBLENotifyConfirm
 };

src/platform/ESP32/nimble/BLEManagerImpl.cpp

@@ -1273,6 +1273,8 @@ CHIP_ERROR BLEManagerImpl::HandleGAPDisconnect(struct ble_gap_event * gapEvent)
     peer_delete(gapEvent->disconnect.conn.conn_handle);
 #endif
 
+    // There can be a case where the BLE central disconnects without unsubscribing from the BLE characteristic.
+    // In such situations, it is necessary to clear the subscription and post a connection error event.
     if (UnsetSubscribed(gapEvent->disconnect.conn.conn_handle))
     {
         CHIP_ERROR disconReason;
@@ -1288,7 +1290,12 @@ CHIP_ERROR BLEManagerImpl::HandleGAPDisconnect(struct ble_gap_event * gapEvent)
             disconReason = BLE_ERROR_CHIPOBLE_PROTOCOL_ABORT;
             break;
         }
-        HandleConnectionError(gapEvent->disconnect.conn.conn_handle, disconReason);
+
+        ChipDeviceEvent connectionErrorEvent;
+        connectionErrorEvent.Type                           = DeviceEventType::kCHIPoBLEConnectionError;
+        connectionErrorEvent.CHIPoBLEConnectionError.ConId  = gapEvent->disconnect.conn.conn_handle;
+        connectionErrorEvent.CHIPoBLEConnectionError.Reason = disconReason;
+        ReturnErrorOnFailure(PlatformMgr().PostEvent(&connectionErrorEvent));
     }
 
     ChipDeviceEvent disconnectEvent;