Managing hardware and software interrupts
Interrupts are signals sent to the processor by hardware devices or software to indicate that an event needs immediate attention. Interrupt handling is a critical function of operating systems that allows efficient response to external events without constant polling. Hardware interrupts are generated by devices like keyboards, mice, network cards, and storage controllers, while software interrupts (also called traps or exceptions) are generated by the CPU itself in response to software events like system calls, divide-by-zero errors, or page faults. The interrupt handling process involves several steps: the CPU finishes its current instruction, saves the current execution context, identifies the interrupt source, jumps to the appropriate interrupt service routine (ISR), executes the ISR, restores the saved context, and resumes normal execution. Modern systems use interrupt controllers (like APIC in x86 systems) to manage multiple interrupt sources and prioritize them. Interrupts can be categorized as maskable (can be disabled by the CPU) or non-maskable (critical interrupts that cannot be disabled). Operating systems also use interrupt priority levels to ensure that critical interrupts are handled promptly. Understanding interrupt handling is essential for system programmers, driver developers, and real-time system designers to create responsive and efficient systems.