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gh-124397: Add threading.iter_locked #133908
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6313b3d
Add iter_locked
eendebakpt 5ced0a9
cleanup
eendebakpt 110332e
cleanup
eendebakpt b675631
📜🤖 Added by blurb_it.
blurb-it[bot] 4406050
update docs
eendebakpt d30ace8
review comments
eendebakpt baec5bc
use explicit lock
eendebakpt e6ea285
Merge branch 'main' into iter_locked
eendebakpt 7315c49
fix import
eendebakpt b7c9d77
cleanup after merge to main
eendebakpt bb98c52
reduce duration of test
eendebakpt 946ee51
use recursive lock
eendebakpt 7e3653a
Merge branch 'main' into iter_locked
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85 changes: 85 additions & 0 deletions
85
Lib/test/test_free_threading/test_threading_iter_locked.py
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,85 @@ | ||
import time | ||
import unittest | ||
from threading import Thread, Barrier, iter_locked | ||
from test.support import threading_helper | ||
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threading_helper.requires_working_threading(module=True) | ||
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class non_atomic_iterator: | ||
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def __init__(self, it): | ||
self.it = iter(it) | ||
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def __iter__(self): | ||
return self | ||
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def __next__(self): | ||
a = next(self.it) | ||
t = time.perf_counter() + 1e-6 | ||
while time.perf_counter() < t: | ||
pass | ||
b = next(self.it) | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Add |
||
return a, b | ||
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def count(): | ||
i = 0 | ||
while True: | ||
i += 1 | ||
yield i | ||
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class iter_lockedThreading(unittest.TestCase): | ||
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@threading_helper.reap_threads | ||
def test_iter_locked(self): | ||
number_of_threads = 10 | ||
number_of_iterations = 8 | ||
barrier = Barrier(number_of_threads) | ||
def work(it): | ||
while True: | ||
try: | ||
a, b = next(it) | ||
assert a + 1 == b | ||
except StopIteration: | ||
break | ||
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data = tuple(range(400)) | ||
for it in range(number_of_iterations): | ||
iter_locked_iterator = iter_locked(non_atomic_iterator(data,)) | ||
worker_threads = [] | ||
for ii in range(number_of_threads): | ||
worker_threads.append( | ||
Thread(target=work, args=[iter_locked_iterator])) | ||
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with threading_helper.start_threads(worker_threads): | ||
pass | ||
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barrier.reset() | ||
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@threading_helper.reap_threads | ||
def test_iter_locked_generator(self): | ||
number_of_threads = 5 | ||
number_of_iterations = 4 | ||
barrier = Barrier(number_of_threads) | ||
def work(it): | ||
barrier.wait() | ||
for _ in range(1_000): | ||
try: | ||
next(it) | ||
except StopIteration: | ||
break | ||
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for it in range(number_of_iterations): | ||
generator = iter_locked(count()) | ||
worker_threads = [] | ||
for ii in range(number_of_threads): | ||
worker_threads.append( | ||
Thread(target=work, args=[generator])) | ||
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with threading_helper.start_threads(worker_threads): | ||
pass | ||
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barrier.reset() | ||
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if __name__ == "__main__": | ||
unittest.main() |
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1 change: 1 addition & 0 deletions
1
Misc/NEWS.d/next/Library/2025-05-11-19-54-05.gh-issue-124397.MwtP6-.rst
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1 @@ | ||
Add :meth:`threading.iter_locked` to make concurrent iteration over an iterable execute using a lock. |
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I'm not sure
non_atomic_iterator
is a good example of something that exists in the wild, because it's not thread-safe on GIL-ful builds either. The thread can arbitrarily switch during execution of Python code, so this would need a lock anyway if concurrent iteration were a use case. For free-threading,__next__
itself should have its own locking to prevent races. How was this design reached?There was a problem hiding this comment.
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The
iter_locked
allows thenon_atomic_iterator
to be used in a threaded-setting, whether in the normal or FT build. Do you have suggestions for other tests?