Chapter 6. Interrupts and Interrupt Handlers
A primary responsibility of the kernel is managing the hardware connected to the machine. As part of this work, the kernel needs to communicate with the machine's individual devices. Given that processors are typically magnitudes faster than the hardware they talk to, it is not ideal for the kernel to issue a request and wait for a response from the potentially slow hardware. Instead, because the hardware is comparatively slow to respond, the kernel must be free to go off, handle other work, and deal with the hardware only after it has actually completed its work. One solution to this problem is polling. Periodically, the kernel can check the status of the hardware in the system and respond accordingly. This incurs overhead, however, regardless of whether the hardware is even active or ready because the polling occurs repeatedly at regular intervals. A better solution is to provide a mechanism for the hardware to signal the kernel when attention is needed. The solution is interrupts.