gh-129069: fix more thread safety issues in list #143019
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colesbury
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Dec 22, 2025
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LGTM
I didn't measure any significant performance difference on fastbench on Apple M4.
Microbenchmarks for list.insert are a little slower on that same machine. Here's the benchmark (courtesy of ChatGPT):
https://gist.github.com/colesbury/b675c95d35f29ca9d5723b95396d48a8
Before:
begin n=100000 reps=1000 total=0.032732s avg=32.73µs/op
middle n=100000 reps=1000 total=0.013755s avg=13.76µs/op
end n=100000 reps=1000 total=0.000564s avg=0.56µs/op
After:
begin n=100000 reps=1000 total=0.048336s avg=48.34µs/op
middle n=100000 reps=1000 total=0.019781s avg=19.78µs/op
end n=100000 reps=1000 total=0.000191s avg=0.19µs/op
We could use ptr_wise_atomic_memmove in many of these places, which will probably be faster in the microbenchmarks, but I'm not sure it'll matter in real programs.
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This PR fixes thread safety of
list.reverseand slice assignment. Also changes stores to use release rather than relaxed as done in #142957.