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Implement Green Threads: Cooperatively Scheduled User-Space Threads

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Language

Compiler

2.0s Limit 256MB

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Implementation

Implement green threads using cooperative scheduling.

Requirements:

Define GreenThread structure with stack, context, state
Implement thread_create() to allocate new green thread
Implement thread_yield() to voluntarily give up CPU
Implement thread_schedule() to switch between threads
Use setjmp/longjmp for context switching
Each thread has its own stack (allocate with malloc)
Maintain thread queue and cycle through ready threads
Demonstrate 3 threads executing in round-robin
Each thread prints messages and yields
Main thread waits for all threads to complete
Print thread switching events

Why This Matters

Go's goroutine runtime, Ruby's Fiber, and pre-1.5 Java's green threads all started from exactly this design: cooperative user-space stacks switched with saved register state instead of kernel involvement. The single-kernel-thread limitation you'll hit here is precisely why early Java green threads were dropped in favor of native threads once multi-core CPUs became common in the early 2000s.

Hints

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Validation Suite

main.c

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