bigreybear opened a new pull request, #11770:
URL: https://github.com/apache/iotdb/pull/11770
## Description
Previously, a NPE could occur due to eviction checks and executions being
performed on different objects.
If two threads, T1 and T2, concurrently decrement the reference count of the
same page, one would be blocked by an exclusive lock before entering eviction
process. Suppose T1 acquires the lock and completes the eviction. Before T2 can
obtain the lock, another thread T3 might acquire it and attempt to read the
evicted page. This action triggers a disk read and creates a new page object,
even while T2 still holds a page object with the same ID. Eventually, when T2
proceeds with eviction, it finds the reference count of its page to be zero and
evicts the page with same ID which is actually held by T3. This erroneous
eviction could subsequently lead to an NPE when T3 finishes all taks and
attempts to evict the same page from the cache.
This PR has:
- [ ] been self-reviewed.
- [ ] concurrent read
- [ ] concurrent write
- [ ] concurrent read and write
- [ ] added documentation for new or modified features or behaviors.
- [ ] added Javadocs for most classes and all non-trivial methods.
- [ ] added or updated version, __license__, or notice information
- [ ] added comments explaining the "why" and the intent of the code
wherever would not be obvious
for an unfamiliar reader.
- [ ] added unit tests or modified existing tests to cover new code paths,
ensuring the threshold
for code coverage.
- [ ] added integration tests.
- [ ] been tested in a test IoTDB cluster.
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##### Key changed/added classes (or packages if there are too many classes)
in this PR
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