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gh-158574: Stabilize TLBC cache refresh tests #158801

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pablogsal merged 2 commits into from
Oct 5, 2026
Merged

gh-158574: Stabilize TLBC cache refresh tests #158801

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1d8afbb
gh-158574: Stabilize TLBC cache refresh tests
pablogsal Oct 4, 2026
9148042
Simplify synchronization in TLBC cache refresh tests
pablogsal Oct 4, 2026
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126 changes: 69 additions & 57 deletions Lib/test/test_external_inspection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2338,42 +2338,50 @@ def test_tlbc_cache_refresh_after_growth(self):
script = textwrap.dedent("""\
import os, threading
from _remote_debugging import RemoteUnwinder
from _queue import SimpleQueue
from test import support

go = threading.Event()
stop = threading.Event()
go = threading.Lock()
stop = threading.Lock()
go.acquire()
stop.acquire()
ready = SimpleQueue()

def leaf():
stop.wait()

def wait_for_leaf_frames(u, expected_count):
for _ in support.sleeping_retry(
support.SHORT_TIMEOUT,
f"Expected {expected_count} leaf frames",
):
try:
traces = u.get_stack_trace()
except RuntimeError as exc:
if str(exc) != "Failed to parse initial frame in chain":
raise
continue
count = sum(
f.funcname == "leaf"
for i in traces
for t in i.threads for f in t.frame_info
)
if count == expected_count:
return
ready.put(None)
stop.acquire()

def start_leaf():
ready.put(None)
go.acquire()
leaf()

def park():
ready.put(None)
stop.acquire()

def leaf_count(u):
return sum(
f.funcname == "leaf"
for i in u.get_stack_trace()
for t in i.threads for f in t.frame_info
)

# SimpleQueue.put() and Lock.acquire() do not push Python frames.
# Once notified, the worker's stack stays stable until go is released.
threading.Thread(target=leaf, daemon=True).start()
ready.get(timeout=support.SHORT_TIMEOUT)
for _ in range(16):
threading.Thread(target=stop.wait, daemon=True).start()
threading.Thread(target=lambda: (go.wait(), leaf()), daemon=True).start()
threading.Thread(target=park, daemon=True).start()
ready.get(timeout=support.SHORT_TIMEOUT)
threading.Thread(target=start_leaf, daemon=True).start()
ready.get(timeout=support.SHORT_TIMEOUT)

u = RemoteUnwinder(os.getpid(), all_threads=True, cache_frames=False)
wait_for_leaf_frames(u, 1)
go.set()
wait_for_leaf_frames(u, 2)
assert leaf_count(u) == 1
go.release()
ready.get(timeout=support.SHORT_TIMEOUT)
assert leaf_count(u) == 2
""")
result = subprocess.run(
[sys.executable, "-X", "gil=0", "-X", "tlbc=1", "-c", script],
Expand All @@ -2397,45 +2405,49 @@ def test_tlbc_cache_refresh_after_slot_fill(self):
script = textwrap.dedent("""\
import os, threading
from _remote_debugging import RemoteUnwinder
from _queue import SimpleQueue

go = threading.Event()
stop = threading.Event()
go = threading.Lock()
stop = threading.Lock()
go.acquire()
stop.acquire()
ready = SimpleQueue()

def leaf():
stop.wait()
ready.put(None)
stop.acquire()

def start_leaf():
ready.put(None)
go.acquire()
leaf()

from test import support

def lines(u, expected_count):
for _ in support.sleeping_retry(
support.SHORT_TIMEOUT,
f"Expected {expected_count} leaf frames",
):
try:
traces = u.get_stack_trace()
except RuntimeError as exc:
if str(exc) != "Failed to parse initial frame in chain":
raise
continue
result = sorted(
f.location.lineno
for i in traces
for t in i.threads for f in t.frame_info
if f.funcname == "leaf"
)
# A new frame can still point at the function definition.
if (len(result) == expected_count and
leaf.__code__.co_firstlineno not in result):
return result
def lines(u):
return sorted(
f.location.lineno
for i in u.get_stack_trace()
for t in i.threads for f in t.frame_info
if f.funcname == "leaf"
)

# SimpleQueue.put() and Lock.acquire() do not push Python frames.
# Once notified, the worker's stack stays stable until go is released.
threading.Thread(target=leaf, daemon=True).start()
threading.Thread(target=lambda: (go.wait(), leaf()), daemon=True).start()
ready.get(timeout=support.SHORT_TIMEOUT)
threading.Thread(target=start_leaf, daemon=True).start()
ready.get(timeout=support.SHORT_TIMEOUT)
u = RemoteUnwinder(os.getpid(), all_threads=True, cache_frames=False)
before = lines(u, 1)
assert before == [8], before
go.set()
cached = lines(u, 2)
assert cached == [8, 8], cached
before = lines(u)
# The notification can be observed before put() returns, so either
# line in leaf() is a valid sample.
assert before in ([12], [13]), before
go.release()
ready.get(timeout=support.SHORT_TIMEOUT)
cached = lines(u)
assert len(cached) == 2, cached
assert all(line in (12, 13) for line in cached), cached
""")
result = subprocess.run(
[sys.executable, "-X", "gil=0", "-X", "tlbc=1", "-c", script],
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