6. What is a device driver in the Linux kernel, and how does it interact with hardware devices?
Answer:
A device driver is a kernel module responsible for facilitating communication between the Linux kernel and hardware devices. It abstracts the intricacies of hardware interaction, providing a standardized interface for the kernel and user space applications to access and control hardware functionality. Device drivers typically register with the kernel and respond to hardware events and requests, such as interrupts, I/O operations, and configuration changes.
7. Explain the role of interrupts in the Linux kernel and how they are handled.
Answer:
Interrupts are signals generated by hardware devices to alert the CPU of events requiring immediate attention, such as data arrival, device errors, or timer expirations. In the Linux kernel, interrupt handling involves several stages:
- Interrupt request (IRQ) handling: The kernel detects and prioritizes incoming interrupts, assigning them to corresponding interrupt handlers.
- Interrupt service routine (ISR) execution: The kernel executes the ISR associated with the triggered interrupt, performing device-specific operations or data processing.
- Interrupt handling completion: Once the ISR completes execution, control returns to the kernel, allowing normal program execution to resume.
8. What are kernel modules in Linux, and how are they loaded and unloaded dynamically?
Answer:
Kernel modules are pieces of code that can be dynamically loaded into or unloaded from the running kernel, providing additional functionality or device support without requiring a kernel recompile. Kernel modules are typically stored as `.ko` files and can be loaded into the kernel using utilities like `insmod` or `modprobe`. Similarly, they can be unloaded using `rmmod` or `modprobe -r`. Kernel modules are useful for extending kernel functionality, supporting new hardware, or adding features without modifying the core kernel source code.
9. Describe the role of locks and synchronization mechanisms in the Linux kernel.
Answer:
Locks and synchronization mechanisms are critical for ensuring data integrity and preventing race conditions in multi-threaded or multi-processor environments. The Linux kernel provides various locking mechanisms, including spinlocks, mutexes, semaphores, and read-write locks, to coordinate access to shared resources and prevent concurrent access conflicts. These mechanisms enable safe and consistent access to kernel data structures, preventing data corruption and ensuring system stability.
10. How does the Linux kernel handle process scheduling, and what are the different scheduling policies available?
Answer:
The Linux kernel employs a multi-level feedback queue scheduler to manage process execution and CPU allocation. The scheduler assigns priorities to processes based on their scheduling class and dynamically adjusts priorities based on process behavior and resource utilization. Linux supports several scheduling policies, including:
- Completely Fair Scheduler (CFS): Ensures fair CPU allocation among processes based on their runtime and priority.
- Real-Time Scheduler (RT): Provides deterministic CPU allocation for real-time tasks with strict timing requirements.
- Deadline Scheduler: Guarantees timely execution of tasks by enforcing deadlines and priorities.
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