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Serialize SemLock bookkeeping for Condition notify #8739

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Merged
youknowone merged 4 commits into from
Sep 19, 2026
Merged

Serialize SemLock bookkeeping for Condition notify #8739

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3e9c150
Serialize SemLock owner bookkeeping around waits
youknowone Sep 19, 2026
fdd78ed
Repeat the Condition.notify_all snippet 20 times
youknowone Sep 19, 2026
1860498
Cover one-by-one Condition.notify in the snippet
youknowone Sep 19, 2026
7c42e17
address review: bound snippet waits with timeouts
youknowone Sep 19, 2026
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Cover one-by-one Condition.notify in the snippet 
Wake a process waiter and a thread waiter with two notify()
calls, not only notify_all(), and keep the 20-repeat loop.

Assisted-by: Grok:4.6
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@youknowone
youknowone committed Sep 19, 2026
commit 1860498fe05e99b480d7327f25d003823ad54f1a
45 changes: 38 additions & 7 deletions extra_tests/snippets/stdlib_multiprocessing_condition.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
"""Thread+process Condition.notify_all must wake every waiter."""
"""Thread+process Condition notify must wake every waiter."""

import multiprocessing
import threading
Expand All @@ -12,8 +12,13 @@ def wait_on_condition(cond, started, woken):
cond.release()


def main():
ctx = multiprocessing.get_context("spawn")
def join_workers(workers):
for worker in workers:
worker.join(timeout=5)
assert not worker.is_alive()


def notify_all_six(ctx):
cond = ctx.Condition()
started = ctx.Semaphore(0)
woken = ctx.Semaphore(0)
Expand All @@ -39,14 +44,40 @@ def main():

for _ in range(6):
woken.acquire()
join_workers(workers)

for worker in workers:
worker.join(timeout=5)
assert not worker.is_alive()

def notify_one_then_the_other(ctx):
cond = ctx.Condition()
started = ctx.Semaphore(0)
woken = ctx.Semaphore(0)

proc = ctx.Process(target=wait_on_condition, args=(cond, started, woken))
proc.daemon = True
proc.start()
thread = threading.Thread(target=wait_on_condition, args=(cond, started, woken))
thread.daemon = True
thread.start()

started.acquire()
started.acquire()

cond.acquire()
cond.notify()
cond.release()
woken.acquire()

cond.acquire()
cond.notify()
cond.release()
woken.acquire()
join_workers([proc, thread])


if __name__ == "__main__":
multiprocessing.freeze_support()
ctx = multiprocessing.get_context("spawn")
# Enough repeats to surface a lost-wakeup race in CI snippets.
for _ in range(20):
main()
notify_all_six(ctx)
notify_one_then_the_other(ctx)
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