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Fix a race condition in DumpStats() during iteration of the ColumnFamilySet (#8714)

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Summary:
DumpStats() iterates through the ColumnFamilySet. There is a potential
race condition because it does Ref the cfd, and the cfd could get
destroyed during the iteration.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8714

Test Plan: make check

Reviewed By: ltamasi

Differential Revision: D30580199

Pulled By: anand1976

fbshipit-source-id: 60a3443ad0d4f7ac6a977dec780e6d2c1b70b850
This commit is contained in:
anand76 2021-08-26 15:39:32 -07:00 committed by Facebook GitHub Bot
parent 4afa24f8ae
commit ebaa3c8a59
2 changed files with 8 additions and 2 deletions
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1
HISTORY.md
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@ -3,6 +3,7 @@
### Bug Fixes
* Allow secondary instance to refresh iterator. Assign read seq after referencing SuperVersion.
* Fixed a bug of secondary instance's last_sequence going backward, and reads on the secondary fail to see recent updates from the primary.
* Fix a race in DumpStats() with column family destruction due to not taking a Ref on each entry while iterating the ColumnFamilySet.
### New Features
* RemoteCompaction's interface now includes `db_name`, `db_id`, `session_id`, which could help the user uniquely identify compaction job between db instances and sessions.

9
db/db_impl/db_impl.cc
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@ -958,8 +958,13 @@ void DBImpl::DumpStats() {
// Release DB mutex for gathering cache entry stats. Pass over all
// column families for this first so that other stats are dumped
// near-atomically.
InstrumentedMutexUnlock u(&mutex_);
cfd->internal_stats()->CollectCacheEntryStats(/*foreground=*/false);
// Get a ref before unlocking
cfd->Ref();
{
InstrumentedMutexUnlock u(&mutex_);
cfd->internal_stats()->CollectCacheEntryStats(/*foreground=*/false);
}
cfd->UnrefAndTryDelete();
}
}