| name | 0.4.3-understand-mcs_lock_enqueue |
| description | [0.4.3] Operation appending a thread-local qnode to the queue tail; atomically CASes qnode into tail; on CAS failure, |
understand-mcs_lock_enqueue
CALL NUMBER: deep_spinlock.mcs_lock_enqueue
DEFINITION: Operation appending a thread-local qnode to the queue tail; atomically CASes qnode into tail; on CAS failure, completes the predecessor's link and retries; ensures FIFO acquisition order.
Invoke this skill to understand mcs_lock_enqueue down to its primitives. The RELATIVE ROOT below is the least-fixed-point closure of everything it bundles from — the full import cone, grouped by the lib each prim comes from. Projected from a prover-typed KB (MAP/SWI-Prolog consistency gate): every reference below resolves.
THE RELATIVE ROOT (the import cone, by lib)
from ?
- atomic_cas (d1): Compare-and-swap operation atomically loading a value, comparing it to an expected value, and storing a new value only if they matched, returning whether the swap occurred.
from deep_spinlock
- mcs_lock_help_links (d1): Backoff resolution protocol during failed enqueue CAS; the thread that lost the CAS follows the discovered pointer chain to complete the linking work of the winner before retrying its own append; prevents starvation under high contention.
CONSUMERS (what needs this)
mcs_lock_acquire, mcs_lock_fifo_ordering
Projected from the concurrency synchronization primitives and memory models KB (155 concepts / 137 relations) — consistency-typed by MAP; the facet list after the colon IS the cross-lib dependency web.
(leaf — this is an actual skill.)
