Kernel of the OS as an Interrupt Handler & used to manage low-level scheduling | A Level | By ZAK

How the kernel of the OS acts as an interrupt handler and how interrupt handling is used to manage low-level scheduling.
The kernel of an operating system plays a crucial role in managing interrupts, which are signals to the processor indicating that an event needs immediate attention. Interrupt handling is a fundamental part of the kernel's responsibilities, playing a key role in managing low-level scheduling and overall system efficiency. Here's an overview of how this works:
Interrupts and the Kernel:
1. Interrupts: An interrupt is a signal from hardware or software indicating an event that needs immediate attention. Hardware interrupts might come from I/O devices (like a keyboard or network card), while software interrupts (also known as traps) are usually generated by programs, for example, when an error occurs.
2. Interrupt Handler: When an interrupt occurs, the processor stops its current activities and switches to a special routine known as an interrupt handler or interrupt service routine (ISR). This is where the kernel comes into play.
Role of the Kernel:
1. Receiving Interrupts: The kernel is configured to receive interrupts at predefined points. When an interrupt is signaled, the control is passed to the kernel.
2. Context Saving: Before handling the interrupt, the kernel saves the context of the current process (such as register values, program counter, etc.) to ensure that it can resume the process later without loss of information.
3. Handling the Interrupt: The kernel determines the cause of the interrupt and calls the appropriate interrupt handler. The handling typically involves servicing the request from the hardware (like reading a byte from a disk into memory).
4. Priority and Scheduling: Some systems prioritize interrupts, allowing more critical operations (like responding to a hardware failure) to pre-empt less critical ones. This is a form of low-level scheduling, ensuring that important tasks are addressed promptly.
5. Resuming Execution: After handling the interrupt, the kernel restores the context of the previously interrupted process and resumes its execution. This might involve decisions about which process to run next (scheduling).
Interrupt Handling and Low-Level Scheduling:
1. Preemptive Multitasking: Interrupts allow for preemptive multitasking, where the kernel can interrupt a running process to give time to a higher-priority process. This is crucial for responsive and efficient system performance.
2. Balancing Performance and Responsiveness: Efficient interrupt handling by the kernel allows the system to balance performance (by not excessively interrupting processes) and responsiveness (by ensuring timely handling of important tasks).
3. Managing I/O Efficiently: Many interrupts are related to I/O operations. The kernel's ability to effectively handle these interrupts ensures that I/O operations do not unnecessarily stall the processor, thereby managing CPU time efficiently.
4. Synchronization: The kernel must also manage synchronization issues that arise due to interrupts, especially in multiprocessor systems, ensuring data integrity and consistency.
In summary, the kernel's role as an interrupt handler is pivotal for the efficient operation of the system. It allows the OS to respond promptly to external and internal events, manage the CPU's time effectively, and maintain a balance between system performance and responsiveness. This mechanism is a foundational aspect of modern operating systems, enabling them to operate in real-time and manage resources effectively.