3.0 Changelog

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The changes made between Beta 2.8 and 3.0 follow. ChronOS 3.0 is a fairly major release, including a rebase to a new kernel, solidifying code which had to change with the move to the different kernel version, and many bug fixes and many new userspace features and improvements.


  • Moved from kernel version to 3.0.24, and updated to the 3.0.24-rt42 version of the PREEMPT_RT patch.
  • Fixed several bugs resulting from changes made between the and 3.0.24 kernels.
  • Allow processes to exit gracefully, even if inside a real-time segment.
  • Ported to ARM architecture.
    • Made MCS Lock implementation more generic. This will allow for easier porting of ChronOS to additional platforms. While the current 'generic' implementation is optimized for x86_64, it has been done in a way that encourages optimized architecture-specific versions.
  • Added DEBUG_CHRONOS config option which adds several checks in the kernel which are useful for debugging (including warning when a ChronOS task blocks inside its RT segment, and when it exits prematurely).
  • Converted all scheduler-managed lists to Linux's 'struct list_head' style lists, and added '#define' constants for referencing them by name.
  • United the initialization of the /proc/chronos/ entries, so that directory is guaranteed to always be created, and made /proc/chronos/schedulers always available, even if scheduling statistics are not enabled.


  • Re-wrote entire sched_test_app for better modularity, portability, and expandability.
    • Remove dependence on QT
    • Add three timing methods: WCET, average-case, and timer-polling.
    • Add array-walk (forwards, backwards, and random), linked list and BST traversal workloads for memory-intensive testing.
    • Improve accuracy of slope-generation mechanism.
    • Add ability to configure groups of threads, which all share memory, and allow that working set size to be configurable via the taskset files.
  • Ported to ARM (fixed several overflow and type issues)
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