Portable Runtime System
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The Portable Runtime System (PRS) is a software library designed to ease the process of porting a RTOS application to a general purpose platform.


  • customizable user space preemptive scheduling;
  • higher single-core context switch performance than usual operating system facilities;
  • dynamic process loading in a common, flat address space;
  • multi-core support through lock-free primitives;
  • Windows support;
  • Linux support.


By default, PRS initializes as many single-threaded priority schedulers as there are CPU cores on the system. Each scheduler manages its own list of tasks to run. New tasks can be created and added to schedulers at run-time. Tasks may also be removed and destroyed. Each task has its own register context and stack; tasks in PRS are light-weight threads, also known as fibers. Fibers provide faster context switching than regular threads because there is no need for the operating system to intervene.

Schedulers work on top of an abstraction which is called a worker. A worker simulates an interruptible bare-metal-like environment where interrupts can occur any time. It handles context switching between scheduler tasks and also manages the flow of execution between an interruptible (preemptible) mode and a non-interruptible mode. In interruptible mode, tasks can be preempted at any time, just like regular threads.

Lock-free PRS data structures ensure that even when some workers are preempted by the OS, other workers can still run freely.

PRS also features a process loader. The process loader loads executables like a regular OS, except that the virtual address space is shared with PRS and other executables. The entry point of the executables is executed through a PRS task. PRS executables are linked with the PR API which features basic services such as message queues, semaphores and task management.

PRS performs OS agnostic operations through its platform abstraction layer (PAL). The PRS PAL currently features operations for managing threads, context switching, virtual memory, exceptions, timers and more.

Tested platforms

  • Windows 7 SP1 with MinGW64, GCC 4.9.3 and 5.3.0
  • RHEL 7.2 with GCC 4.8.5 (use C99=1)
  • Debian 8.3 with GCC 4.9.2

PRS only supports AMD64 architectures for now.


On Windows, first install MinGW-w64. If MinGW binaries are not acessible through the PATH environment variable, you may define the MINGW_HOME to point to them. For example, set MINGW_HOME=C:\MinGW. Then, run make in the root PRS directory.

On Linux, make sure the gcc and g++ tools are installed, then run make.

Test code can be run using the test make target.

If C11 is not supported by your compiler, use the C99=1 assignation on the make command line. PRS can make use of C11 features such as the stdatomic.h header and the _Thread_local specifier.

To compile in a debug configuration, use the DEBUG=1 assignation.

Getting started

The prs.log file is generated upon execution of PRS in the current working directory.

Examples in the examples directory show how to build dynamically loaded PRS executables.

The include/pr.h file contains the APIs that are used by PRS executables.

The prs/init.c file contains the PRS initialization and exit sequences.


This version of PRS is released under the [GNU Affero General Public License] (https://www.gnu.org/licenses/agpl-3.0.en.html).

For inquiries about a commercial license, please contact portableruntimesystem@gmail.com