test fix

Author: GuillaumeLagrange

report.md

@@ -1,51 +1,27 @@
-# Segfault in `instrument_hooks_deinit` during Python shutdown
+# Segfault in instrument hooks during Python shutdown
 
 ## Issue
 
 CI job `tests (valgrind, 3.13, >=8.1.1)` crashes with exit code 139 (SIGSEGV) after all tests pass.
-The segfault occurs during Python's shutdown/GC phase, not during test execution.
 
 Failing CI run: https://github.com/CodSpeedHQ/pytest-codspeed/actions/runs/23649460934/job/68890119732
 
-## Root cause (suspected)
+## Root cause
 
-`InstrumentHooks.__del__` calls `instrument_hooks_deinit()` via cffi during Python shutdown.
-When multiple `InstrumentHooks` instances are created (e.g. the xdist test loops 5 times, each creating a new instance), their destructors fire during GC at exit and crash — likely because the native library or cffi runtime is already partially torn down.
+Calling `sys.activate_stack_trampoline("perf")` multiple times after loading a cffi native library causes a segfault at process exit on CPython 3.13.12 (works fine on 3.13.11). This is a CPython regression.
 
-## Stack trace (from CI)
+`InstrumentHooks.__init__` unconditionally calls `sys.activate_stack_trampoline("perf")`. When multiple instances are created (e.g. the xdist test loops 5 times inprocess), the repeated activation triggers the crash.
 
-```
-Fatal Python error: Segmentation fault
-  File "plugin.py", line 148 in pytest_configure
-  ...
-  File "test_pytest_plugin_cpu_instrumentation.py", line 116 in test_pytest_xdist_concurrency_compatibility
-```
+## Fix
 
-## Minimal repro
+Guard the trampoline activation with `sys.is_stack_trampoline_active()` in `InstrumentHooks.__init__`:
 
 ```python
-# repro.py
-import os
-os.environ["CODSPEED_ENV"] = "1"
-
-from pytest_codspeed.instruments.hooks import InstrumentHooks
-
-for i in range(5):
-    h = InstrumentHooks()
-    print(f"Created instance {i}: {h.instance}")
-
-del h
-print("Exiting...")
-```
-
-```
-uv run python repro.py
-# Segfaults at exit with code 139
+if SUPPORTS_PERF_TRAMPOLINE and not sys.is_stack_trampoline_active():
+    sys.activate_stack_trampoline("perf")
 ```
 
-## Key files
+## Verification
 
-- `src/pytest_codspeed/instruments/hooks/__init__.py` — `InstrumentHooks.__del__` calls `instrument_hooks_deinit`
-- `src/pytest_codspeed/instruments/hooks/build.py` — cffi bindings for the native library
-- `src/pytest_codspeed/instruments/analysis.py` — creates `InstrumentHooks` in `__init__`
-- `tests/test_pytest_plugin_cpu_instrumentation.py::test_pytest_xdist_concurrency_compatibility` — triggers the bug by creating 5 successive instances
+- `uv run --python 3.13.12 python repro.py` → exit 0 (was exit 139)
+- `test_pytest_xdist_concurrency_compatibility` → PASSED, exit 0 (was exit 139)

repro1_single_no_delete.py

@@ -0,0 +1,8 @@
+"""Test 1: Single instance, no explicit delete — crash at shutdown?"""
+import os
+os.environ["CODSPEED_ENV"] = "1"
+from pytest_codspeed.instruments.hooks import InstrumentHooks
+
+h = InstrumentHooks()
+print(f"Created: {h.instance}")
+print("Exiting (no explicit delete)...")

repro2_single_explicit_deinit.py

@@ -0,0 +1,11 @@
+"""Test 2: Single instance, explicit deinit + del — crash?"""
+import os
+os.environ["CODSPEED_ENV"] = "1"
+from pytest_codspeed.instruments.hooks import InstrumentHooks
+
+h = InstrumentHooks()
+print(f"Created: {h.instance}")
+h.lib.instrument_hooks_deinit(h.instance)
+print("Deinited explicitly")
+del h
+print("Deleted, exiting...")

repro3_multi_eager_cleanup.py

@@ -0,0 +1,20 @@
+"""Test 3: Multiple instances, explicit deinit before exit — does eager cleanup fix it?"""
+import os
+os.environ["CODSPEED_ENV"] = "1"
+from pytest_codspeed.instruments.hooks import InstrumentHooks
+
+instances = []
+for i in range(5):
+    h = InstrumentHooks()
+    print(f"Created instance {i}: {h.instance}")
+    instances.append(h)
+
+for i, h in enumerate(instances):
+    h.lib.instrument_hooks_deinit(h.instance)
+    # Prevent __del__ from calling deinit again
+    del h.instance
+    del h.lib
+    print(f"Cleaned up instance {i}")
+
+del instances
+print("Exiting...")

repro4_multi_skip_deinit.py

@@ -0,0 +1,13 @@
+"""Test 4: Multiple instances, skip deinit entirely — confirm deinit is the crash site."""
+import os
+os.environ["CODSPEED_ENV"] = "1"
+from pytest_codspeed.instruments.hooks import InstrumentHooks
+
+# Monkey-patch __del__ to do nothing
+InstrumentHooks.__del__ = lambda self: print(f"Skipping deinit for {self.instance}")
+
+for i in range(5):
+    h = InstrumentHooks()
+    print(f"Created instance {i}: {h.instance}")
+
+print("Exiting (deinit skipped)...")

src/pytest_codspeed/instruments/hooks/__init__.py

@@ -37,7 +37,7 @@ def __init__(self) -> None:
         if self.instance == 0:
             raise RuntimeError("Failed to initialize CodSpeed instrumentation library.")
 
-        if SUPPORTS_PERF_TRAMPOLINE:
+        if SUPPORTS_PERF_TRAMPOLINE and not sys.is_stack_trampoline_active():
             sys.activate_stack_trampoline("perf")  # type: ignore
 
     def __del__(self):