Fix a race condition in RWVar
#433
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jorisdral
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This is now ready for review. My takeaway is that from now on I should put more thought into interruptibility when writing exception safe code 😝 |
jasagredo
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Oct 23, 2024
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`prop_noRace` is updated to properly test interleavings of threads, and threads can now be cancelled asynchronously. This unearths a subtle race condition in `unsafeAcquireWriteAccess`, which contains interruptible operations that leave the internal state of `RWVar` in an unrecoverable state if they happen in just the right place.
This mainly involves rolling back previous `RWState` changes if an interrupt happens. The code is extended with comments to explain how the code is now interrupt-safe.
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retryis interruptible, which can leave theRWVarin a state that is unrecoverable.Kudos to @jasagredo for finding this subtle bug!