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audit-jmm

Testing & Quality
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Java Memory Model audit of all VarHandle/volatile field access modes

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Source SKILL.md: https://github.com/ben-manes/caffeine/blob/HEAD/.claude/skills/audit-jmm/SKILL.md

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Perform a Java Memory Model audit of the cache.

For every field accessed via VarHandle or Unsafe, and for every field declared volatile or accessed under synchronization:

  1. State the field name, type, and declared access mode.
  2. List every read and write with: access mode, method/line, locks held.
  3. For each (write, read) pair: state whether happens-before is guaranteed. If it depends on access mode, verify BOTH sides use compatible modes.
  4. Identify any field where:
    • Plain/opaque write paired with plain/opaque read across threads with no intervening synchronization
    • Code relies on opaque providing ordering beyond coherence
    • Volatile read on one field but non-volatile on a correlated field

Specific areas to examine:

  • writeTime: encodes both timestamp and refresh-in-progress flag
  • accessTime: is opaque access sufficient for expiration?
  • key/value fields: do value reads provide visibility of the object's fields?
  • policyWeight vs weight: correlated but updated at different times

For each issue:

  • State the specific reordering or visibility failure
  • Construct a concrete 2-thread execution
  • Verify the execution is legal under the JMM (not just TSO)

Do not report issues that only affect performance. Do not report deliberately racy patterns with documented stale-read tolerance.

Platform focus: Pay specific attention to aarch64 (ARM) memory ordering. ARM's weaker-than-TSO model exposes reordering bugs invisible on x86. Historical bug: WeakValueReference.keyReference required setRelease + storeStoreFence (not just setRelease alone) because the field is non-final and aarch64 reorders the field write after reference publication. Check for similar patterns — non-final fields published via release without a fence.