Interrupts – The Heartbeat of a Unix Kernel
6 days ago
- #operating-systems
- #cpu-architecture
- #interrupts
- Modern operating systems are event-driven, relying on interrupts to handle events like network packets, user inputs, and hardware signals.
- Interrupts work by stopping the CPU's current task, jumping to a predefined memory location (interrupt service handler), executing instructions, and then resuming the original task.
- Key CPU registers involved in interrupts include EIP (instruction pointer) and ESP (stack pointer), which help manage the execution flow and stack operations.
- Interrupts are numbered (256 vectors) and managed via the Interrupt Descriptor Table (IDT), which maps each interrupt to its handler.
- Sources of interrupts include hardware (e.g., keyboard, timer), software (e.g., exceptions, INT instruction), and complex routing mechanisms like PIC, APIC, and MSI.
- Interrupts enable efficient I/O handling (e.g., DMA for disk reads) and preemptive multitasking, ensuring fair CPU time allocation even if a process hangs.
- Interrupts also facilitate debugging, inter-core communication, and privilege level changes (e.g., switching between kernel and user space).