In closing, how can you query and/or change the scheduling policy and (real-time) priority of a kernel thread? The kernel provides APIs for this (the sched_setscheduler_nocheck() API is often used within the kernel). As a practical example, the kernel will require kernel threads for the purpose of servicing interrupts – the threaded interrupt model, which we covered in Chapter 4, Handling Hardware Interrupts, in the Internally implementing the threaded interrupt section).
It creates these threads (via kthread_create()) and changes their scheduling policy and real-time priority via the sched_setscheduler_nocheck() API. We won't explicitly cover their usage here as we covered this in the companion guide Linux Kernel Programming - Chapter 11, The CPU Scheduler – Part 2. It's interesting: the sched_setscheduler_nocheck() API is just a simple...
