fix: race condition in update lock lets two updates run at once#27
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Adityakk9031 wants to merge 1 commit into
Open
fix: race condition in update lock lets two updates run at once#27Adityakk9031 wants to merge 1 commit into
Adityakk9031 wants to merge 1 commit into
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close:#26
The update lock had a classic TOCTOU bug. When the lock was stale, the code would:
Between step 2 and 3, another process could grab the lock. Now both processes think they own it, so both fire off uv tool upgrade or pip install at the same time. Corrupts the install.
The fix uses os.replace() to atomically swap in the new lock — no window between removing the old one and planting the new one. Also added a read-back safety check: after the replace, we verify our PID is still in the file. If another process raced past us, we detect it and back off.
Tests cover all the paths: fresh lock, non-stale refusal, stale replacement, and the race-lost scenario.