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Data race between _PyMonitoring_RegisterCallback and _Py_call_instrumentation_2args in instrumentation.c #131141
Description
Bug report
Bug description:
I built cpython 3.13 from source with TSAN and running the following code:
import sys
import concurrent.futures
import threading
if __name__ == "__main__":
num_workers = 20
num_runs = 100
barrier = threading.Barrier(num_workers)
tool_id = 3
event_id = sys.monitoring.events.CALL
sys.monitoring.use_tool_id(tool_id, "test_tool_1")
sys.monitoring.set_events(tool_id, event_id)
def closure():
barrier.wait()
def my_callback(code, instruction_offset, callable, arg0):
pass
sys.monitoring.register_callback(tool_id, event_id, my_callback)
def example_function():
a = 1
b = 2
c = a + b
for _ in range(num_runs):
example_function()
with concurrent.futures.ThreadPoolExecutor(max_workers=num_workers) as executor:
futures = []
for i in range(num_workers):
futures.append(executor.submit(closure))
assert len(list(f.result() for f in futures)) == num_workersTSAN reports the following data race: https://gist.github.com/vfdev-5/e80f9b4528993eb1543e45a9216350e3#file-repro-log
cpython version:
Python 3.13.2+ experimental free-threading build (heads/3.13:9e0fce413a9, Mar 12 2025, 00:48:15) [Clang 18.1.3 (1ubuntu1)]
CPython versions tested on:
3.13
Operating systems tested on:
Linux
Activity
kumaraditya303 commentedon Mar 12, 2025
On current main TSAN report:
The data race is because the callback is being read here without atomic whereas it was exchanged with atomics.
cpython/Python/instrumentation.c
Line 976 in e0637ce
gh-131141: fix data race in instrumentation while registering callback (
pythongh-131141: fix data race in instrumentation while registering c…
[3.13] gh-131141: fix data race in instrumentation while registering …
pythongh-131141: fix data race in instrumentation while registering c…