Recently I came over a couple of bugs in the kernel of HACK-RTOS for eZ80. Both are in the scheduler. First one relates to semaphores. With certain conditions it could lead to unnecessary scheduler invocations after release of a semaphore. The second bug might have caused the real-time thread not to receive CPU time right after a less prioritized thread releases a mutex that the real-time thread wants to lock. The fixed version of HACK-RTOS is here: depositfiles.com/files/6czjvodwp