RTOS Terms

C

Callback
Context Switch A context switch is the act of saving the CPU state of a currently running task (or thread) and restoring the previously saved state of anot...
Critical Section A critical section is a region of code that must execute with mutual exclusion with respect to other concurrent activities that share the sa...

D

Deadlock A deadlock is a situation in which two or more tasks are each waiting for a resource held by another, such that none can proceed and all rem...

F

FreeRTOS FreeRTOS is an open-source, real-time operating system kernel widely used in embedded systems, providing preemptive multitasking (with coope...

I

Interrupt An interrupt is a hardware or software signal that causes the processor to suspend its current execution context, save some or all state (th...

L

Latency In RTOS and embedded systems contexts, latency is the elapsed time between a triggering event and the system's first observable response to ...

M

Message Queue A message queue is a synchronization and communication primitive that lets tasks, ISRs, and processes exchange discrete data items through a...
Mutex A mutex (mutual exclusion object) is a synchronization primitive that allows at most one task or thread to hold it at a time, protecting a s...

N

Nested Interrupts Nested interrupts occur when a higher-priority interrupt preempts an ISR that is already executing, causing the processor to suspend the cur...

P

Preemption
Priority Inheritance Priority inheritance is a mutex protocol in which a low-priority task temporarily receives the priority of the highest-priority task blocked...
Priority Inversion Priority inversion is a scheduling anomaly in which a high-priority task is indirectly blocked by a lower-priority task, because an intermed...

R

Race Condition A race condition is a defect in which the correctness of a program depends on the relative timing or interleaving of two or more concurrent ...
Rate Monotonic Scheduling Rate Monotonic Scheduling (RMS) is a fixed-priority preemptive scheduling algorithm for periodic real-time tasks in which each task is assig...
Reentrancy
Round-Robin Scheduling Round-robin scheduling is a CPU scheduling policy in which each ready task is given a fixed time slice (quantum) in turn, cycling through al...

S

Scheduler A scheduler is the component of an RTOS (or bare-metal framework) responsible for deciding which task or thread runs on the CPU at any given...
Semaphore A semaphore is a synchronization primitive that uses an integer counter to control access to shared resources or to signal events between ta...
Spinlock A spinlock is a synchronization primitive in which a thread or task repeatedly polls a lock variable in a tight loop ("spins") until the loc...
Stack Overflow A stack overflow occurs when a program writes beyond the allocated bounds of its call stack, typically by consuming more stack space than wa...

W

Worst-Case Execution Time Worst-Case Execution Time (WCET) is the longest time a given piece of code can take to complete across all possible inputs, data states, and...

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