Check out my first novel, midnight's simulacra!
FreeRTOS
From dankwiki
FreeRTOS is an open source real time operating system commonly used in embedded development.
Task notifications
Rather than using semaphores for wakeup, task notifications are faster and less heavyweight.
Mutexes
FreeRTOS mutexes are a special class of semaphores. Note that they cannot be taken in interrupt handlers (i.e. xSemaphoreTakeFromISR() should only be used on semaphores created using xSemaphoreCreateBinary()). Using xSemaphoreTakeFromISR() on a mutex-type semaphore will generally fail if the lock is already held.
