Mastering Embedded Linux Programming - Second Edition

Threaded interrupt handlers

Not all interrupts are triggers for real-time tasks, but all interrupts steal cycles from real-time tasks. Threaded interrupt handlers allow a priority to be associated with the interrupt and for it to be scheduled at an appropriate time, as shown in the following diagram:

If the interrupt-handler code is run as a kernel thread, there is no reason why it cannot be preempted by a user space thread of higher priority, and so the interrupt handler does not contribute toward scheduling latency of the user space thread. Threaded interrupt handlers have been a feature of mainline Linux since 2.6.30. You can request that ...