interrupts
Introduction
event that alters the normal flow of a program
can be generated by hardware devices or by the CPU itself
physically produced by electronic signals generated by hardware and directed to the input pins on an
interrupt controller.
Types of Interrupts
Based on the source of interrupt :
Synchronous → Generated by executing an instruction (Eg : syscalls, Divide by Zero)
Asynchronous → Based on external event (Eg : Key presses on keyboard)
Based on ability to temporarily disable :
Maskable → can be ignored; it is signaled via INT pin
Non-Maskable → cannot be ignored ; it is signaled via NMI pin
Interrupt Controllers
An interrupt controller is a simple chip that multiplexes multiple interrupt lines into a single interrupt line on the processor.
when an interrupt occurs, the current flow of execution is stopped and the interrupt handler runs (unless interrupts are disabled for critical sections)
Each interrupt has a unique value assigned to it so that interrupts from 2 different devices can be differentiated. These values are called
Interrupt Request (IRQ) lines.
Interrupt Flow
TODO: add flow excali svg here
Top Halves
Bottom Halves
TODO: add backlinks here
Their are 4 ways to defer work in Bottom Half
softirq
tasklet
workqueue (replacement of task queues)
kernel Timer
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