lock-free-guidelisted

# Lock-Free / Wait-Free Concurrency Guidelines ## Requirements - C11 atomics (`<stdatomic.h>`); applies to systems code with atomic, threading, and job-scheduling primitives. ## Essentials - **No data races** - Every shared mutable location touched by 2+ threads is atomic or lock-protected, see [references/memory-model.md](references/memory-model.md) - **CAS loops retry** - `compare_exchange_weak` in a loop; reload the expected value on failure, see [references/atomics-and-cas.md](references/atomics-and-cas.md) - **Lock-free needs reclamation** - Removing a node from a shared structure is not freeing it, see [references/safe-memory-reclamation.md](references/safe-memory-reclamation.md) - **Measure, do not assume** - Locks are often faster; profile before going lock-free, see [references/progress-guarantees.md](references/progress-guarantees.md) ## Memory model - **Progress guarantees** - wait-free ⊃ lock-free ⊃ obstruction-free ⊃ blocking, see [references/progress-guarantees.md](references/progress-guarantees.md) - **Happens-before** - Acquire/release builds the ordering that makes writes visible, see [references/memory-model.md](references/memory-model.md) - **Orderings** - relaxed/acquire/release/acq_rel/seq_cst + fences, see [references/memory-ordering.md](references/memory-ordering.md) ## Building blocks - **Atomics & CAS** - load/store/exchange/fetch\_\*/compare_exchange, weak vs strong, see [references/atomics-and-cas.md](references/atomics-and-cas.md) - **ABA p