songgaoye opened a new pull request, #3615:
URL: https://github.com/apache/brpc/pull/3615
### What problem does this PR solve?
Issue Number: resolve
Problem Summary:
`ObjectPool` and `ResourcePool` access `_free_chunks` from multiple threads.
`pop_free_chunk()` checked `_free_chunks.empty()` before acquiring
`_free_chunks_mutex`, while `push_free_chunk()` modifies the same vector
under
the mutex. Concurrent reads and writes of `std::vector` metadata are a C++
data
race; vector growth can also invalidate the metadata being read.
### What is changed and the side effects?
Changed:
- Remove the unlocked `_free_chunks.empty()` fast path in `ObjectPool`.
- Remove the same unlocked access in `ResourcePool`.
- Protect every access to `_free_chunks` in `pop_free_chunk()` with
`_free_chunks_mutex`.
Side effects:
* Performance effects:
`pop_free_chunk()` now acquires the mutex even when no free chunk is
available. This removes the unsafe empty-cache fast path and ensures
correct
synchronization with concurrent returns.
* Breaking backward compatibility:
None.
* * *
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