Yanqin Jin 570d490a3d Fix a race condition caused by unlocking db mutex (#5294)
Summary:
Previous code may call `~ColumnFamilyData` in `DBImpl::AtomicFlushMemTablesToOutputFiles` if the column family is dropped or `cfd->IsFlushPending() == false`. In `~ColumnFamilyData`, the db mutex is released briefly and re-acquired. This can cause correctness issue. The reason is as follows.

Assume there are more bg flush threads. After bg_flush_thr1 releases the db mutex, bg_flush_thr2 can grab it and pop an element from the flush queue. This will cause bg_flush_thr2 to accidentally pick some memtables which should have been picked by bg_flush_thr1. To make the matter worse, bg_flush_thr2 can clear `flush_requested_` flag for the memtable list, causing a subsequent call to `MemTableList::IsFlushPending()` by bg_flush_thr1 to return false, which is wrong.

The fix is to delay `ColumnFamilyData::Unref` and `~ColumnFamilyData` for column families not selected for flush until `AtomicFlushMemTablesToOutputFiles` returns. Furthermore, a bg flush thread should not clear `MemTableList::flush_requested_` in `MemTableList::PickMemtablesToFlush` unless atomic flush is not used **or** the memtable list does not have unpicked memtables.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5294

Differential Revision: D15295297

Pulled By: riversand963

fbshipit-source-id: 03b101205ca22c242647cbf488bcf0ed80b2ecbd
2019-05-15 11:23:47 -07:00
..
2019-04-10 19:31:18 -07:00
2019-04-10 19:31:18 -07:00
2019-04-30 10:13:28 -07:00
2017-10-17 08:57:09 -07:00
2017-07-15 16:11:23 -07:00
2018-12-17 17:33:46 -08:00
2018-10-04 20:46:50 -07:00
2018-10-04 20:46:50 -07:00
2017-07-15 16:11:23 -07:00
2017-07-15 16:11:23 -07:00
2017-07-15 16:11:23 -07:00
2019-04-10 19:31:18 -07:00
2017-07-15 16:11:23 -07:00
2017-07-15 16:11:23 -07:00
2018-08-24 18:13:20 -07:00
2017-07-15 16:11:23 -07:00
2017-07-15 16:11:23 -07:00
2017-07-15 16:11:23 -07:00
2017-07-15 16:11:23 -07:00
2019-04-19 20:33:04 -07:00
2017-07-15 16:11:23 -07:00
2017-07-15 16:11:23 -07:00
2017-07-15 16:11:23 -07:00