Fix a deadlock involving scheduler.all_digests, and add a note. (cherrypick of #11723)
#11726
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…sbuild#11723) ### Problem By chance, a garbage collection thread started up and called `lease_files_in_graph` while I happened to be running Pants in the foreground. This caused a deadlock because `lease_files_in_graph` was not releasing the GIL before touching the `Graph` (via the `Scheduler`)... and foreground interactions with the `Graph` frequently need to acquire the GIL to check for equality. ### Solution Move the problematic call to `scheduler.all_digests()` under `allow_threads` and add a note. Additionally, move one other potentially-problematic method call under `allow_threads`. ### Result A rare (hopefully?) deadlock is prevented. See pantsbuild#11722 for how we might make this less likely in the future. [ci skip-build-wheels]
Eric-Arellano
approved these changes
Mar 17, 2021
jsirois
approved these changes
Mar 17, 2021
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Problem
By chance, a garbage collection thread started up and called
lease_files_in_graphwhile I happened to be running Pants in the foreground. This caused a deadlock becauselease_files_in_graphwas not releasing the GIL before touching theGraph(via theScheduler)... and foreground interactions with theGraphfrequently need to acquire the GIL to check for equality.Solution
Move the problematic call to
scheduler.all_digests()underallow_threadsand add a note. Additionally, move one other potentially-problematic method call underallow_threads.Result
A rare (hopefully?) deadlock is prevented. See #11722 for how we might make this less likely in the future.
[ci skip-build-wheels]