VxWorks by Wind River Systems is a mature, high-performance real-time operating system (RTOS) deployed in numerous mission-critical systems. Its rich set of features supports multitasking, deterministic behavior, connectivity, and modular design. In this article, we dive into the basic RTOS functions in VxWorks — the kernel services, task management, synchronization primitives, IPC (inter-process communication), and virtual devices.
Along the way, we’ll link to related VxWorks blogs for deeper reading (e.g. VxWorks 7 tutorials, device driver development, ARINC-653 topics).
1. VxWorks: Overview & Platform Strategy #
1.1 Core Attributes & Design #
- VxWorks offers a Unix-like, multitasking environment optimized for real-time performance
- Modular and hierarchical architecture — only needed OS components are built in
- Developed via a host–target model: you build on Windows, Linux, or Unix hosts and deploy to embedded targets
- Supports Device Software Optimization, helping reduce development time and increase reliability
1.2 Kernel & Portability Layer #
VxWorks 6.x introduces a processor abstraction layer (PAL) that decouples hardware dependencies. This lets you port applications to new hardware by replacing only the low-level interface.
Supported architectures include ARM, MIPS, Intel, ColdFire, SuperH, and more.
2. Modern RTOS Requirements & VxWorks 6.9 Enhancements #
As embedded systems evolve, so do their demands:
- More connectivity, remote management, and security
- Use of complex processors and multi-core architectures
- Need to consolidate functionality while preserving real-time guarantees
To address these, VxWorks 6.9 extends support for asymmetric multiprocessing (AMP) and symmetric multiprocessing (SMP) with optimized multicore acceleration.
3. Core Kernel Capabilities & System Services #
3.1 Scheduling & Task Execution #
- Full support for preemptive scheduling and round-robin
- Ability to execute tasks in kernel mode
- Tasks have separate contexts (TCB), ISRs use a shared stack
- Kernel provides preemption points, context switching, and task control
3.2 Inter-Process Communication & Synchronization #
VxWorks offers a rich IPC suite:
- Semaphores (binary, mutex, counting) for synchronization
- Queues and pipes for message passing
- POSIX-compliant IPC when POSIX extensions are enabled
Tasks pending on IPC may be unblocked according to priority or FIFO order.
3.3 Signal Handling & Software Interrupts #
- Signals act like software interrupts for exception or event handling
- You can register a signal handler and connect it to an interrupt vector
- Useful when you want asynchronous callback behavior in tasks
3.4 Virtual Device & I/O Support #
- Pipe drivers let you treat IPC channels as devices
- Socket interfaces enable network-transparent communication
- RAM disk drivers, network drivers, and other virtual devices help abstract hardware
3.5 System, Timing, and Error Support #
- System-level primitives: OS startup, clock rate configuration, enable/disable interrupts
- Watchdog timers for recovery and fault detection
- Power management APIs to control energy usage
- Memory protection, error detection, and reporting mechanisms
3.6 Kernel Naming Conventions #
- VxWorks functions do not use
OS_oros_prefixes- e.g.,
taskInit()
- e.g.,
- Options and macros use the
VX_prefix- e.g.,
VX_PRIVATE_ENVorVX_NO_STACK_FILL
- e.g.,
4. Task Management & Control Flow #
4.1 Task Lifecycle #
Key states and operations:
- Creation / Initialization
- Activation / Running
- Suspension / Resumption
- Pending / Timeout
- Deletion / Control operations
You can also spawn a task (i.e. create + activate in one step).
4.2 Context Isolation & Safe Deletion #
VxWorks protects against race conditions: for example, you cannot delete a task that is waiting on a message from another if it would leave it in an inconsistent state.
Priority inheritance is supported to mitigate priority inversion.
5. Synchronization: Semaphores & Queues #
5.1 Semaphores #
- Binary / mutex semaphores: for mutual exclusion
- Counting semaphores: for resource pools or signaling
- Using POSIX mode, you also get P / V style semantics
Unblocking rules: priority-based or FIFO-based depending on configuration.
5.2 Queues #
- Queues store actual message data (not only pointers)
- Supports priority posting (i.e.
postFront) - Pending tasks are unblocked either by priority or FIFO order
6. Signal (Software Interrupt) Handling #
Signals are useful for asynchronous notifications:
- You register a signal-service function (C routine)
- Use
signalConnect()(or equivalent) to bind it to a vector - When an event or exception occurs, the handler is invoked
This mechanism blends software interrupts into task-level logic.
7. Virtual Devices & Driver Abstraction #
VxWorks provides virtual device support to make I/O and IPC more flexible:
- Pipe drivers treat pipes like devices
- Sockets enable transparent network communication
- Network drivers interface with Ethernet, shared memory, etc.
- RAM disk (memory-resident filesystems)
These abstractions allow you to use uniform APIs across different hardware setups.
8. Related Reading & Internal Links #
To help readers dive deeper, here are some recommended internal links from vxworks6.com:
- Getting Started With VxWorks 7 on QEMU: Step-by-Step Guide — useful for those porting from VxWorks 6 to 7.
- Why Upgrade to VxWorks 7 — covers benefits of moving to VxWorks 7.
- Device Tree-Based Driver Development in VxWorks 7.0 — a good follow-up when writing drivers.
- VxWorks 653 Multi-core Edition: Comprehensive Product Overview — for those interested in ARINC-653 and safety-critical RTOS.
- Writing an I²C Driver in VxWorks 7: Complete Example — practical coding tutorial in the VxWorks 7.
9. Final Thoughts & SEO Touches #
In summary, mastering these basic RTOS functions in VxWorks gives you a solid platform for building real-time, deterministic, connected embedded systems.
From kernel services and task control to semaphores, queues, signals, and device abstractions, these primitives form the building blocks for reliable software.