dtourolle
f53af260a2
9c5ce5festablished "a node never sleeps with a wake outstanding" and implemented it as two independent atomics: queued_ for "a firing is in flight", wake_pending_ for "a wake arrived during one". Two variables cannot express that invariant, because the release side has to read and write both and a wake can land in between: producer (try_submit) worker (release_and_recheck) ------------------------ ---------------------------- CAS reads queued_ == true, fails queued_.store(false) wake_pending_.exchange(false) -> false wake_pending_.store(true) queued_ false, wake_pending_ true, nothing running and nothing scheduled — exactly the state the invariant forbids. This is not a memory-ordering subtlety; the interleaving holds under seq_cst. SubmitGate replaces both with one atomic over three states, so "idle" and "wake outstanding" are the same variable and no interleaving can produce both. A release that finds a recorded wake keeps the claim and hands it to the next firing, so the node is never momentarily idle while a submission for it is in flight. What this does not do is fix a reproducible hang. Every current call site follows release_and_recheck() with a level re-check — on_input_ready(), or outputs_have_space() on the parked path — which rediscovers the state a lost wake would have signalled. The bug is masked, and I could not write a node-level test that fails before and passes after; claiming otherwise would be dishonest. The masking is a property of the call sites, not the mechanism: any future early return that forgets its re-check reintroduces a silent hang, and the pipeline has already been round that loop twice (28e0667, then9c5ce5f, each of which moved the stall rather than removing it). So the tests are structural. The state machine is pinned by contract tests, and the defect it replaces is pinned by demonstration: LegacyGate in the test file is the old protocol with a seam between the failed CAS and the wake record, which makes the loss deterministic rather than something to wait for. It also keeps the defect on record now that the code implementing it is gone. Also ignores build-*/ so a sanitizer build tree cannot be committed by accident, which this commit did on its first attempt.
80 lines
3.4 KiB
CMake
80 lines
3.4 KiB
CMake
cmake_minimum_required(VERSION 3.21)
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# ── Catch2 ────────────────────────────────────────────────────────────────────
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find_package(Catch2 3 QUIET)
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if(NOT Catch2_FOUND)
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include(FetchContent)
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FetchContent_Declare(
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Catch2
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GIT_REPOSITORY https://github.com/catchorg/Catch2.git
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GIT_TAG v3.5.3
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)
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FetchContent_MakeAvailable(Catch2)
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endif()
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# ── Google Test ───────────────────────────────────────────────────────────────
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find_package(GTest QUIET)
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if(NOT GTest_FOUND)
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include(FetchContent)
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FetchContent_Declare(
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googletest
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GIT_REPOSITORY https://github.com/google/googletest.git
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GIT_TAG v1.14.0
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)
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FetchContent_MakeAvailable(googletest)
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endif()
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# ── Test executable ───────────────────────────────────────────────────────────
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add_executable(kpn_tests
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test_fixed_string.cpp
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test_traits.cpp
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test_channel.cpp
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test_node.cpp
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test_network.cpp
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test_static_network.cpp
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test_shared_resource.cpp
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test_pool_node.cpp
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test_backpressure_deadlock.cpp
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test_scheduler.cpp
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test_submit_gate.cpp
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)
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target_link_libraries(kpn_tests PRIVATE
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kpn
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Catch2::Catch2WithMain
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GTest::gtest
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)
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# ── Channel stress suite (separate executable) ────────────────────────────────
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# Contended SPSC tests for the lock-free Channel<T>. Kept out of kpn_tests
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# because each case runs many reps / tens of thousands of items and is slow.
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# Most valuable under -DKPN_SANITIZER=thread, but correct (and run) without it.
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add_executable(kpn_tests_stress test_channel_stress.cpp)
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target_link_libraries(kpn_tests_stress PRIVATE kpn Catch2::Catch2WithMain)
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# ── Sanitizer flags ───────────────────────────────────────────────────────────
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# kpn_sanitizer_flags() is defined in the top-level CMakeLists and is a no-op
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# unless -DKPN_SANITIZER=... is set. Sanitizer must be on both compile and link.
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kpn_sanitizer_flags(_kpn_san)
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if(_kpn_san)
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foreach(_t kpn_tests kpn_tests_stress)
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target_compile_options(${_t} PRIVATE ${_kpn_san})
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target_link_options(${_t} PRIVATE ${_kpn_san})
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endforeach()
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endif()
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include(CTest)
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include(Catch)
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# DISCOVERY_MODE PRE_TEST defers test enumeration to `ctest` run time. The
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# default (POST_BUILD) runs each test binary during the build to list its
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# cases — which fails a sanitizer build: a TSan/ASan binary needs a fixed
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# address-space layout and aborts on startup ("unexpected memory mapping")
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# under the container's ASLR, breaking the build before any test runs. The
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# tsan.yaml job invokes the binaries directly (not via ctest), so deferring
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# discovery costs nothing there and keeps `ctest` working for normal builds.
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catch_discover_tests(kpn_tests DISCOVERY_MODE PRE_TEST)
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# Register the stress suite under its own label so CI can run / time it
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# separately from the fast unit tests.
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catch_discover_tests(kpn_tests_stress DISCOVERY_MODE PRE_TEST PROPERTIES LABELS "stress")
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