The outermost hold takes a ticket under the gate and, after releasing it,
waits on a per-cache delivery gate for its turn, delivers, then advances
the turn. Delivery order across threads equals admission order. A hold
closed while its thread is delivering queues its ticket behind that
delivery on the same thread instead of waiting, so an observer writing
the cache cannot deadlock against a writer: a waiting thread holds no gate
and no turn, and a turn holder never waits.
Hand-over-hand from the gate to a delivery lock was rejected: a writer
blocked on the delivery lock while holding the gate deadlocks with an
observer that writes the same cache.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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