Inter-processor interrupt

In computing, an inter-processor interrupt (IPI), also known as a shoulder tap, is a special type of interrupt by which one processor may interrupt another processor in a multiprocessor system if the interrupting processor requires action from the other processor. Actions that might be requested include: Flush memory management unit caches, such as translation lookaside buffers, on other processors when memory mappings are changed by one processor; Stop when the system is being shut down by one processor.

Source: Wikipedia — Inter-processor interrupt (CC BY-SA 4.0)