Add validation of lock ordering #116
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Pull Request Overview
This PR adds validation of lock ordering to ensure that only a single element lock is held at once and to prevent taking the expiry lock while holding an element lock. Key changes include:
- Replacing direct lock/unlock calls with methods that return a release token and require passing that token for unlocking.
- Introducing a new LockOrderGuard class that tracks lock ownership and validates lock ordering.
- Updating multiple modules (TimeDelayedElement, LRUElementList, InnerArc, ExpiredElementList, Element, and Arc) to integrate the new lock validation mechanism.
Reviewed Changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| lib/src/main/java/eu/aylett/arc/internal/TimeDelayedElement.java | Updated lock usage to capture and use a release token |
| lib/src/main/java/eu/aylett/arc/internal/LockOrderGuard.java | New guard class to enforce lock ordering |
| lib/src/main/java/eu/aylett/arc/internal/LRUElementList.java | Modified locking to use the new release-based mechanism |
| lib/src/main/java/eu/aylett/arc/internal/InnerArc.java | Added assertions to ensure no element lock is held during eviction lock operations |
| lib/src/main/java/eu/aylett/arc/internal/ExpiredElementList.java | Updated lock handling with release tokens |
| lib/src/main/java/eu/aylett/arc/internal/Element.java | Refactored lock and unlock to work with LockOrderGuard |
| lib/src/main/java/eu/aylett/arc/Arc.java | Integrated LockOrderGuard and updated element locking usage |
| } | ||
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| @EnsuresLockHeld("this.lock") | ||
| public void lock() { | ||
| @MayReleaseLocks | ||
| public LockOrderGuard.Release lock() { |
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Consider adding a JavaDoc comment here to clarify that the lock method returns a release token which must be used in the corresponding unlock(LockOrderGuard.Release) method.
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| return evictionLock.tryLock(); | ||
| } | ||
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| @EnsuresLockHeld("this.evictionLock") | ||
| @ReleasesNoLocks | ||
| public void takeEvictionLock() { | ||
| lockOrderGuard.assertNoElementLockHeld(); |
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Consider adding a comment to explain why asserting that no element lock is held before acquiring the eviction lock is crucial for maintaining the lock order invariants.
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This ensures we only take a single element lock at once, and also that we don't try to take the expiry lock while holding an element lock. Taking an element lock while holding the expiry lock is expected.
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This ensures we only take a single element lock at once, and also that we don't try to take the expiry lock while holding an element lock.
Taking an element lock while holding the expiry lock is expected.