How can I restart the menu bar in Unity?

My Unity menu bar is no longer working. Clicking on top-level menu items (on the right hand general menu items, or on the app-specific items on the left) registers visually, but menus don't drop down. (For example, clicking on the microphone icon causes the icon to flash, noting I clicked there, but the sound menu does not drop down).

How can I restart the menu bar without exiting Unity.

You can do this by restarting Unity:

• You can press Alt+F2, then type "unity", then click Enter to restart unity.

• Or you can run below command in terminal to restart Unity:

  setsid unity