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QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
Programming
Getting Started with the QNX OS
Getting Started with the QNX OS: A Guide for Realtime Programmers is intended to introduce you to the QNX OS and help you develop applications and resource managers for it.
Processes and Threads
This chapter explains the concepts behind processes and threads, and the challenges of synchronization and scheduling. A thread is a flow of execution, and a process is a collection of threads. In the QNX OS, the schedulable entity is a thread, not a process.
More on synchronization
Interprocess synchronization
Suppose two or more processes are sharing memory. They might want to synchronize the activities of different threads in different processes, just as they would between threads in the same process. All the various POSIX thread (pthread) synchronization tools available (mutexes, condition variables, barriers, etc) can be shared between proceses.

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
- Quickstart Guide
- System Architecture
  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
- OS Components & Operations
- Graphics
- Programming
  - Getting Started with the QNX OS
    Getting Started with the QNX OS: A Guide for Realtime Programmers is intended to introduce you to the QNX OS and help you develop applications and resource managers for it.
    - Processes and Threads
      This chapter explains the concepts behind processes and threads, and the challenges of synchronization and scheduling. A thread is a flow of execution, and a process is a collection of threads. In the QNX OS, the schedulable entity is a thread, not a process.
      - Process and thread fundamentals
        Before we start talking about threads, processes, time slices, and all the other wonderful scheduling concepts, let's establish an analogy.
      - The kernel's role
        The house analogy is excellent for getting across the concept of synchronization, but it falls down in one major area. In our house, we had many threads running simultaneously. However in a single-processor system, only one thing can run at once.
      - Threads and processes
        Let's return to our discussion of threads and processes, this time from the perspective of a real live system. Then, we'll take a look at the function calls used to deal with threads and processes.
      - More on synchronization
        Readers/writer locks
        Readers and writer locks are used for exactly what their name implies: multiple readers can be using a resource, with no writers, or one writer can be using a resource with no other writers or readers.
        Condition variables
        Another common situation that occurs in multi-threaded programs is the need for a thread to wait until something happens. This something could be anything! It could be the fact that data is now available from a device, or that a conveyor belt has now moved to the proper position, or that data has been committed to disk, or whatever. Another twist to throw in here is that several threads may need to wait for the given event.
        Interprocess synchronization
        Suppose two or more processes are sharing memory. They might want to synchronize the activities of different threads in different processes, just as they would between threads in the same process. All the various POSIX thread (pthread) synchronization tools available (mutexes, condition variables, barriers, etc) can be shared between proceses.
        Pools of threads
        Another thing that QNX OS has added is the concept of thread pools. You'll often notice in your programs that you want to run a certain number of threads but also to control the behavior of those threads within certain limits.
        An example of synchronization
        Let's look at an example of synchronization in a multithreaded program.
      - Scheduling and the real world
        So far we've talked about scheduling policies and thread states, but we haven't said much yet about why and when things are rescheduled.
    - Message Passing
      In this chapter, we'll look at the most distinctive feature of QNX OS, message passing. Message passing lies at the heart of the operating system's microkernel architecture, giving the OS its modularity.
    - Interrupts
      In this chapter, we'll take a look at interrupts, how we deal with them under QNX OS, their impact on scheduling and realtime, and some interrupt-management strategies.
    - Resource Managers
      In this chapter, we'll take a look at what you need to understand in order to write a resource manager. Resource managers are another distintive feature of QNX OS that allow you to access services through standard POSIX calls.
    - Sample Programs
      This appendix contains the complete versions of some of the sample programs discussed in this book.
    - Glossary
  - Programmer's Guide
    The QNX OS Programmer's Guide covers a variety of topics that might interest developers who are building applications that will run under the QNX OS.
  - Writing a Resource Manager
- System Security Guide
  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX OS system and developers who want to create a QNX OS resource manager free from vulnerabilities.
- Utilities & Libraries
- Migrating to QNX OS 8.0
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX software in Amazon Web Services (AWS) and Microsoft Azure (Azure).
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX^® Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX^® Operating System (OS) applications and systems.
QNX Hypervisor and QNX Hypervisor for Safety
The QNX Hypervisor and QNX Hypervisor for Safety products allow you to run multiple OSs on a target system so you can separate critical and non-critical functions, support a wide variety of applications, and reduce hardware costs.
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

Interprocess synchronization

QNX SDP8.0Getting Started with the QNX OSDeveloperUser

Suppose two or more processes are sharing memory. They might want to synchronize the activities of different threads in different processes, just as they would between threads in the same process. All the various POSIX thread (pthread) synchronization tools available (mutexes, condition variables, barriers, etc) can be shared between proceses.

You must configure these mechanisms to support synchronization across processes by setting the PTHREAD_PROCESS_SHARED flag when you initialize them. So if you're using condvars, for instance, set this flag when calling pthread_condattr_init().

You can share semaphores between processes too. Unnamed semaphores (i.e., those created with sem_init()) must be initialized with the pshared parameter set to a non-zero value. Named semaphores (i.e., those created with sem_open()) are inherently shared between processes through the pathname space.

Page updated: June 11, 2026