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22d4dc5066
Summary: EndWriteStall has a data race: `queue_.empty()` is checked outside of the mutex, so once we enter the critical section another thread may already have cleared the list, and accessing the `front()` is undefined behavior (and causes interesting crashes under high concurrency). This PR fixes the bug, and also rewrites the logic to make it easier to reason about it. It also fixes another subtle bug: if some writers are stalled and `SetBufferSize(0)` is called, which disables the WBM, the writer are not unblocked because of an early `enabled()` check in `EndWriteStall()`. It doesn't significantly change the locking behavior, as before writers won't lock unless entering a stall condition, and `FreeMem` almost always locks if stalling is allowed, but that is inevitable with the current design. Liveness is guaranteed by the fact that if some writes are blocked, eventually all writes will be blocked due to `stall_active_`, and eventually all memory is freed. While at it, do a couple of optimizations: - In `WBMStallInterface::Signal()` signal the CV only after releasing the lock. Signaling under the lock is a common pitfall, as it causes the woken-up thread to immediately go back to sleep because the mutex is still locked by the awaker. - Move all allocations and deallocations outside of the lock. Pull Request resolved: https://github.com/facebook/rocksdb/pull/9009 Test Plan: ``` USE_CLANG=1 make -j64 all check ``` Reviewed By: akankshamahajan15 Differential Revision: D31550668 Pulled By: ot fbshipit-source-id: 5125387c3dc7ecaaa2b8bbc736e58c4156698580 |
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| .. | ||
| alloc_tracker.cc | ||
| hash_linklist_rep.cc | ||
| hash_skiplist_rep.cc | ||
| inlineskiplist.h | ||
| inlineskiplist_test.cc | ||
| memtablerep_bench.cc | ||
| skiplist.h | ||
| skiplist_test.cc | ||
| skiplistrep.cc | ||
| stl_wrappers.h | ||
| vectorrep.cc | ||
| write_buffer_manager.cc | ||
| write_buffer_manager_test.cc | ||