.. include:: <mmlalias.txt>


OS Primitives: Interrupt Handling
=================================

.. topic:: Documentation

   * :doc:`../why-os/interrupts`
   * Zephyr: Interrupt Service Routine APIs
     <https://docs.zephyrproject.org/latest/doxygen/html/group__isr__apis.html>`__

IRQs And ISRs
-------------

* Interrupt service routine (ISR): callback ``void(int irqnum)``
* Attached to an Interrupt request (IRQ) ``irqnum``
* Called *asynchronously* (run at the most inopportune time)
* IRQ should safely be considered parallel (though varies per
  architecture)

.. literalinclude:: code/isrdemo.cpp
   :caption: :download:`code/isrdemo.cpp`
   :language: c++

.. code-block:: console
   :caption: In ``why-shell``

   > irq 2
   seeing interrupt #2
   >