Linux Driver Development with Raspberry Pi - Wait Queues : LDD with Raspberry Pi #19

In this video, we explore Wait Queues in Linux Device Driver Development and understand how they are used to implement blocking and non-blocking I/O in kernel drivers. First, we review the difference between blocking and non-blocking operations in Linux. Then we implement both behaviors in a character device driver on Raspberry Pi, using a GPIO interrupt triggered by a push button to simulate incoming data. Initially, we demonstrate a busy-wait blocking approach using cpu_relax(), and analyze why this method is problematic. You will see how busy-waiting wastes CPU resources, prevents signal handling, and can even stop a kernel module from unloading properly. After understanding the limitations of busy-waiting, we introduce Linux Wait Queues, the correct kernel mechanism for putting processes to sleep efficiently. We replace the busy-wait loop with wait_event_interruptible() and wake the process using wake_up_interruptible() from the interrupt handler. By the end of this video, you will understand: * What blocking and non-blocking I/O mean in Linux drivers * How O_NONBLOCK works in user space * Why busy-wait loops are dangerous in kernel drivers * How wait queues allow processes to sleep without consuming CPU * How interrupts can wake sleeping processes safely This is an essential concept for building efficient and reliable Linux device drivers. GitHub :- https://github.com/madhawapolkotuwa/linux_driver_development_with_raspberrypi ☕Buy me a Coffee : https://buymeacoffee.com/madhawapolb #linuxkernel #linuxprogramming #kernel