[[PATCH stalld] 00/33] Test suite hardening, correctness fixes, and BPF optimization
Wander Lairson Costa <[email protected]> Wed, 20 May 2026 11:00:27 -0300
| Newsgroups | org.kernel.vger.linux-rt-users |
|---|---|
| Message-ID | <[email protected]> |
The stalld functional test suite has accumulated significant reliability and maintainability issues over time. Several tests were silently passing due to missing assertions, shell scoping bugs that discarded subshell results, and grep substring matches causing false positives on multi-digit CPU systems. Massive boilerplate duplication existed across the suite, timing-dependent sleeps caused flakiness, and a daemon bug was discovered where --force_fifo combined with single-threaded mode silently fell back to adaptive mode instead of erroring out. Additionally, the BPF queue_track backend suffered from an O(n) linear array scan on every sched_wakeup event, consuming significant real-time latency budget in Telco workloads. This series addresses these issues in three areas. First, the daemon's --force_fifo validation is fixed to reject the incompatible single-threaded mode at startup. Second, the test suite is overhauled by introducing eight shared helpers (test_section, cleanup_scenario, find_starved_child, init_functional_test, assert_stalld_rejects, assert_log_contains, assert_success, and starvation/boost assertion helpers) that replace duplicated validation patterns across all functional tests. The tests are then hardened with proper assertions, transitioned to fail-fast semantics where any failure immediately aborts the run, and timing-dependent sleeps are replaced with event-driven synchronization. The starvation_gen helper's signal handler is fixed for async-signal safety. Legacy C test infrastructure, stale documentation, and unreachable code are removed. Third, the BPF queue_track backend replaces its per-CPU linear array with a hash map keyed by (cpu, pid) for O(1) task lookups, reducing thread latency from 5-6us to 3us on real-time systems. As a result, approximately seven previously silent tests now correctly validate daemon behavior, the suite runs deterministically via event-driven waits rather than fixed sleeps, and the BPF backend eliminates its lookup overhead entirely. The series yields a net reduction of roughly 9,850 lines (+874/-10,725). Wander Lairson Costa (33): stalld: Reject --force_fifo in single-threaded mode tests: Introduce test_section() helper tests: Introduce cleanup_scenario() helper tests: Introduce starvation and boost asserts tests: Introduce find_starved_child() helper tests: Fix task exit timing in test_boost_restoration tests: Consolidate and adopt init_functional_test() tests: Introduce assert_stalld_rejects() helper tests: Fix boost verification in runtime and duration tests tests: Fix subshell swallowing test results tests: Fix repeated log match finding same line chore: Remove legacy test infrastructure and stale docs tests: Add assertions to SCHED_OTHER restoration test tests: Fix CPU selection grep substring matches tests: Add idle CPU skipping assertion tests: Remove redundant pkill from cleanup tests: Introduce and adopt assert_log_contains() helper tests: Remove weak, redundant, and assertion-free test blocks tests: Introduce and adopt assert_success() helper tests: Replace wait conditionals with asserts tests: Remove if-wrappers around assert calls tests: Abort immediately on test failure tests: Remove dead code after making fail() fatal tests: Introduce and adopt process helpers tests: Extract wait_for_process_exit helper tests: Reduce default wait timeouts tests: Reduce starvation_gen durations tests: Replace init sleeps in test_affinity tests: Drop redundant sleeps in test_pidfile tests: Remove redundant sleeps after start_stalld tests: Reduce timing and replace sleeps with event waits tests: Fix async-signal-unsafe handler bpf: Replace linear task scan with hash map .claude/CLAUDE.md | 585 --------- .claude/agents/agent-prompt-engineer.md | 135 -- .claude/agents/c-expert.md | 53 - .claude/agents/code-reviewer.md | 104 -- .claude/agents/get-agent-hash | 99 -- .claude/agents/git-scm-master.md | 1154 ----------------- .claude/agents/kernel-hacker.md | 231 ---- .claude/agents/plan-validator.md | 130 -- .claude/agents/project-historian.md | 285 ---- .claude/agents/project-librarian.md | 604 --------- .claude/agents/project-manager.md | 388 ------ .claude/agents/project-scope-guardian.md | 326 ----- .claude/agents/python-expert.md | 57 - .claude/agents/test-specialist.md | 656 ---------- .claude/agents/update-agent-hashes | 96 -- .claude/context-snapshot.json | 103 -- .claude/rules | 42 - .gitignore | 5 +- bpf/stalld.bpf.c | 206 ++- src/queue_track.c | 95 +- src/queue_track.h | 107 +- src/utils.c | 9 +- tests/BACKEND_USAGE.md | 269 ---- tests/CONTEXT_SNAPSHOT_2025-10-31.md | 231 ---- tests/Makefile | 29 +- tests/README.md | 29 +- tests/TODO.md | 727 ----------- tests/functional/test_affinity.sh | 178 +-- tests/functional/test_backend_selection.sh | 24 +- tests/functional/test_boost_duration.sh | 164 +-- tests/functional/test_boost_period.sh | 151 +-- tests/functional/test_boost_restoration.sh | 310 +---- tests/functional/test_boost_runtime.sh | 179 +-- tests/functional/test_cpu_selection.sh | 76 +- tests/functional/test_deadline_boosting.sh | 266 +--- tests/functional/test_fifo_boosting.sh | 269 +--- .../test_fifo_priority_starvation.sh | 197 +-- tests/functional/test_force_fifo.sh | 196 +-- tests/functional/test_foreground.sh | 65 +- tests/functional/test_idle_detection.sh | 195 +-- tests/functional/test_log_only.sh | 30 +- tests/functional/test_logging_destinations.sh | 38 +- tests/functional/test_pidfile.sh | 166 +-- tests/functional/test_runqueue_parsing.sh | 417 ------ tests/functional/test_starvation_detection.sh | 281 +--- tests/functional/test_starvation_threshold.sh | 138 +- tests/functional/test_task_merging.sh | 161 +-- tests/helpers/starvation_gen.c | 2 +- tests/helpers/test_helpers.sh | 356 +++-- tests/legacy/README.md | 169 --- tests/legacy/test01.c | 506 -------- tests/legacy/test01_wrapper.sh | 161 --- tests/run_tests.sh | 149 +-- 53 files changed, 874 insertions(+), 10725 deletions(-) delete mode 100644 .claude/CLAUDE.md delete mode 100644 .claude/agents/agent-prompt-engineer.md delete mode 100644 .claude/agents/c-expert.md delete mode 100644 .claude/agents/code-reviewer.md delete mode 100755 .claude/agents/get-agent-hash delete mode 100644 .claude/agents/git-scm-master.md delete mode 100644 .claude/agents/kernel-hacker.md delete mode 100644 .claude/agents/plan-validator.md delete mode 100644 .claude/agents/project-historian.md delete mode 100644 .claude/agents/project-librarian.md delete mode 100644 .claude/agents/project-manager.md delete mode 100644 .claude/agents/project-scope-guardian.md delete mode 100644 .claude/agents/python-expert.md delete mode 100644 .claude/agents/test-specialist.md delete mode 100755 .claude/agents/update-agent-hashes delete mode 100644 .claude/context-snapshot.json delete mode 100644 .claude/rules delete mode 100644 tests/BACKEND_USAGE.md delete mode 100644 tests/CONTEXT_SNAPSHOT_2025-10-31.md delete mode 100644 tests/TODO.md delete mode 100755 tests/functional/test_runqueue_parsing.sh delete mode 100644 tests/legacy/README.md delete mode 100644 tests/legacy/test01.c delete mode 100755 tests/legacy/test01_wrapper.sh -- 2.54.0