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gh-159534: Fix race condition in test_sampling_profiler #160028

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Merged
vstinner merged 2 commits into from
Oct 21, 2026
Merged

gh-159534: Fix race condition in test_sampling_profiler #160028

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gh-159534: Fix race condition in test_sampling_profiler
vstinner Oct 21, 2026
2ae1251
Remove redundant sys.platform check
vstinner Oct 21, 2026
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39 changes: 10 additions & 29 deletions Lib/test/test_profiling/test_sampling_profiler/test_children.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
SHORT_TIMEOUT,
reap_children,
requires_remote_subprocess_debugging,
sleeping_retry,
)

# Guard imports that require _remote_debugging module.
Expand Down Expand Up @@ -84,29 +85,13 @@ def reader():
return result[0]


def _wait_for_process_ready(proc, timeout):
# Wait for a subprocess to be ready using polling instead of fixed sleep.
# Returns True if process is ready, False if it exited or timeout.
deadline = time.time() + timeout
poll_interval = 0.01

while time.time() < deadline:
if proc.poll() is not None:
return False

try:
if sys.platform == "linux":
if os.path.exists(f"/proc/{proc.pid}/exe"):

@vstinner vstinner Oct 21, 2026

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I'm not sure of the purpose of the old test. Just after fork, /proc/pid/exe is a symlink to the Python executable (and it does exist). After fork+exec, /proc/pid/exe is a symlink to /usr/bin/sleep (which also exists). I don't see when /proc/pid/exe doesn't exist.

return True
else:
return True

@vstinner vstinner Oct 21, 2026

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On non-Linux platforms, this function basically did nothing. So in my change, I only call the function on Linux.

except OSError:
pass

time.sleep(poll_interval)
poll_interval = min(poll_interval * 2, 0.1)

return proc.poll() is None
def _wait_for_process_exec(proc, name, timeout):
# Wait until a child process calls exec() to replace the forked process
# executable. Raise AssertionError on timeout.
for _ in sleeping_retry(timeout, max_delay=0.1):
exe = os.readlink(f"/proc/{proc.pid}/exe")
if os.path.basename(exe) == name:
break


@unittest.skipIf(
Expand Down Expand Up @@ -634,17 +619,13 @@ def test_is_python_process_non_python_subprocess(self):
"""Test that a non-Python subprocess is not detected as Python."""
# Start a non-Python subprocess (sleep command)
proc = subprocess.Popen(
["sleep", "10"],
["sleep", "60"],
stdout=subprocess.DEVNULL,
stderr=subprocess.DEVNULL,
)

try:
# Wait for process to be ready using polling
self.assertTrue(
_wait_for_process_ready(proc, SHORT_TIMEOUT),
f"Process {proc.pid} should be ready within {SHORT_TIMEOUT}s",
)
_wait_for_process_exec(proc, "sleep", SHORT_TIMEOUT)

self.assertFalse(
is_python_process(proc.pid),
Expand Down
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