Interrupt latency
Another factor of concern for realtime systems is the amount of time taken between the generation of the hardware interrupt and the first line of code executed by the ISR.
Atomic operations
Some convenience functions are defined in the include file <atomic.h> that allow you to perform atomic operations (i.e., operations that are guaranteed to be indivisible or uninterruptible).
Interrupts and power management
In order to help the kernel save power, you can make an interrupt “lazy” by specifying an acceptable latency for it.