Linux kernel interrupt management
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. This is achieved by means of interrupts. An interrupt is a signal that’s 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, and whose main job consists of routing interrupts to CPUs.
An interrupt may have five states:
- Active: An interrupt that has been acknowledged by a processing element (PE) and is being handled. While being handled, another assertion of the same interrupt is not presented as an interrupt to a processing element, until the initial interrupt is no longer active.
- Pending (asserted): An interrupt that is recognized as asserted in hardware, or generated...
