The Design and Construction of a User - Level Kernel

| Multithreading is a powerful programming paradigm that has become very popular in recent years. The authors have developed a set of course materials and software tools for eeectively teaching multithreaded programming (MTP). One important component of the au-thors' system is a very simple user-level kernel for instructors to teach MTP without getting into system details , and for the students to add extensions. This paper presents the design and implementation of this kernel as well as its use in the classroom. This minimal user-level kernel employs a rst-come-rst-served scheduling policy , and permits a user to create and join threads, and use mutex locks. With this kernel, students are able to implement semaphores, barriers, reader-writer locks, mailboxes and condition variables. This approach has two advantages: (1) students can easily learn the basics and internal of a kernel that supports MTP, and (2) conventional debuggers can be used for debugging purposes, because the kernel is a user-level program.