Kernel interrupt handling
Apart from servicing processes and user requests, another job of the Linux kernel is managing and speaking with hardware. This is either from the CPU to the device or from the device to the CPU and is achieved by means of interrupts. An interrupt is a signal sent to the processor by an external hardware device requesting immediate attention. Prior to an interrupt being visible to the CPU, this interrupt should be enabled by the interrupt controller, which is a device on its own whose main job consists of routing interrupts to CPUs.
The Linux kernel allows the provision of handlers for interrupts we are interested in so that when those interrupts are triggered, our handlers are executed.
An interrupt is how a device halts the kernel, telling it that something interesting or important has happened. These are called IRQs on Linux systems. The main advantage interrupts offer is to avoid device polling. It is up to the device to tell if there is a change...
