Ghost Kernel

The redux branch has now support for kernel-level threads and threaded system calls. The previous implementation only supported userspace-threads which had some advantages but also made specific call implementations more complicated. This approach will improve efficiency and allows a better scheduling implementation in the long run.

There were some interesting problems to solve; due to the fact that a kernel thread might get interrupt while holding a kernel lock, the g_mutex implementation must now keep track of the number of locks held per processor. As long as a task holds kernel locks, no other task will be scheduled until the task is finished with its work.

System calls can now be registered as threaded or direct calls. When a threaded call is executed, the respective handler is called within a kernel-level thread. These processing tasks are reused for successive system calls by the same task. This allows preemption during call processing and avoids blocking the scheduler for long-running requests.