Concurrency, happens-before and race freedom
Research context
postgraduate concept · established · As of 2026-10-10
Sequential consistency presents operations in one order preserving each thread's program order.
Key knowledge
Sequential consistency presents operations in one order preserving each thread's program order. The C++ concurrency design distinguishes synchronization/atomic operations from conflicting unsynchronized ordinary accesses. In its simpler model with default sequentially consistent atomics, data-race-free programs receive sequentially consistent behavior. Relaxed or acquire/release atomics can be free of ordinary data races without providing a single sequentially consistent global execution; their ordering requires separate memory-model reasoning.
Conditions and scope
- The cited 2008 paper explains the C++ design foundation, not every clause of a later C++ standard. The DRF-to-SC guarantee here excludes explicitly weakened low-level atomic orders.
- A happens-before relation supplies specified ordering; compiler reordering and weak hardware must be analyzed against the actual language model. A data race is not synonymous with every logical race, and mutex use alone does not prove an application invariant.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Author checked this English statement, displayed equation where present and stated hypotheses against these source locations: Sections 1.2/2 and Theorem 7.1: DRF sequential consistency with default sequentially consistent atomics; Section 9: weakened low-level atomic orders. The check is bounded to the recorded claims; no complete proof reconstruction, software proof replay or universal literature completeness is claimed.
2026-10-10 · Author source-body/statement/equation/domain check, with graph associations scoped individually. Separate independent content/source/inventory review is required before branch closure.
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