Basic functions of real-time kernel

The kernel is the core of the RTOS that controls the processor, memory and devices and provides services to the tasks. Its basic functions are:

1. Task (process) management: create, delete, suspend, resume, change priority; maintains a task control block (TCB) and task states (ready, running, blocked).
2. Scheduling: selects the next task to run, normally the highest-priority ready task, pre-emptively, with a bounded decision time.
3. Context switching: saves and restores the CPU context when tasks change.
4. Inter-task communication and synchronisation: semaphores, mutexes, mailboxes, message queues, event flags and shared memory.
5. Timer and time management: the system tick, delays, time-outs, periodic tasks, software timers.
6. Interrupt management: handles interrupt entry and exit, ISR-to-task communication, nested interrupts.
7. Memory management: allocation and freeing of memory (fixed-size blocks to avoid fragmentation), protection.
8. Device (I/O) management: device drivers and a standard interface for peripherals.
9. Resource management: controlled sharing of resources, avoiding deadlock and priority inversion (priority inheritance).
10. File system and networking services (in larger RTOS).