refactor(rcu): extract grace period state machine - #2216
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fslongjin merged 1 commit intoAug 29, 2026
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Replace the redundant grace-period fields with a small deterministic state machine that owns sequence advancement, request coalescing, waiting CPU snapshots, and wrap-safe completion checks. Track callback generations with wrap-safe tickets and serialize lock-free callback draining through a single owner so rcu_barrier cannot observe out-of-order completion. Keep the existing worker, queue layout, public APIs, and debug snapshot contract unchanged. Document the ordinary non-preemptible RCU contract in code, make read guards task-bound, and place full memory barriers only at GP start, real quiescent-state reports, GP completion, and synchronous return boundaries. Add deterministic coverage for nested requests, empty masks, consecutive grace periods, sequence wraparound, callback ticket wraparound, drainer ownership, and callbacks admitted during an active GP. Tests: - make fmt - make kernel - /opt/tests/dunitest/bin/normal/rcu_selftest_test (QEMU, twice) Signed-off-by: longjin <longjin@dragonos.org>
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Summary
Compatibility
The existing public RCU APIs, worker model, callback queue layout, and debug snapshot format remain unchanged.
Testing
make fmtmake kernel/opt/tests/dunitest/bin/normal/rcu_selftest_testin a 2-vCPU QEMU guest, run twice (2/2 passed each run)Closes #2209