Implementing Kernel Threads in xv6
Go beyond processes — a practical guide to adding real kernel threads to a teaching OS.
Summary
xv6 gives you processes, but not threads. This article goes into the kernel and adds them: shared address spaces, new system calls, and a scheduler that understands threads. It blends the theory of concurrency with the very concrete work of editing an operating system and watching it run.
Processes are isolated; threads share. This guide takes the xv6 teaching kernel and gives it true kernel threads — shared memory, new system calls, and a scheduler that knows the difference — bridging OS theory and hands-on kernel hacking.
Key ideas
- 01 A thread is a process that shares its address space with siblings.
- 02 New syscalls (clone/join) are needed to create and reap threads.
- 03 The scheduler and trap frames must be adapted to schedule threads, not just processes.
- 04 Synchronization becomes essential the moment memory is shared.
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