2dc6bc51b4
Summary: The parallel-compression auto-skip feature (https://github.com/facebook/rocksdb/issues/15079) introduced a data race that TSAN reports in block_based_table_reader_test. In StateTransition(), the auto-skip loop reads ring_buffer[cslot].auto_skip_bypassed speculatively, from a not-yet-committed atomic_state snapshot, before the CAS that would validate that snapshot. Unlike every other BlockRep field (touched only after a successful CAS grants exclusive slot ownership), a stale snapshot can point that read at a physical ring-buffer slot the emit thread is concurrently recycling for a new block in EmitBlockForParallel, racing the plain write there. The speculative result is discarded when the CAS fails, so there is no logical corruption, but the plain read/write is a data race (UB) and is flagged by TSAN. Make auto_skip_bypassed a RelaxedAtomic<bool> so the speculative read and the emit-thread write are atomic. Relaxed ordering suffices: correctness of the auto-skip decision is still gated by the CAS, and when the CAS succeeds the value was published by the emit thread through the existing acquire/release ordering on atomic_state and is not modified elsewhere. Pull Request resolved: https://github.com/facebook/rocksdb/pull/15094 Test Plan: Covered by existing block_based_table_reader_test parameterizations that build with parallel compression (parallel_threads > 1) under TSAN, which is where the race was originally reported. Reviewed By: joshkang97 Differential Revision: D115777206 Pulled By: pdillinger fbshipit-source-id: 7ee969ec2d95890255d2e8b76eceaa5876b82170
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key-value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it especially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/main/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Questions and discussions are welcome on the RocksDB Developers Public Facebook group and email list on Google Groups.
License
RocksDB is dual-licensed under both the GPLv2 (found in the COPYING file in the root directory) and Apache 2.0 License (found in the LICENSE.Apache file in the root directory). You may select, at your option, one of the above-listed licenses.