Summary:
With TSAN build on CircleCI (see mini-tsan in .circleci/config).
Sometimes `SeqAdvanceConcurrentTest.SeqAdvanceConcurrent` will get stuck when an experimental feature called
"unordered write" is enabled. Stack trace will be the following
```
Thread 7 (Thread 0x7f2284a1c700 (LWP 481523) "write_prepared_"):
#0 0x00000000004fa3f5 in __tsan_atomic64_load () at ./db/merge_context.h:15
https://github.com/facebook/rocksdb/issues/1 0x00000000005e5942 in std::__atomic_base<unsigned long>::load (this=0x7b74000012f8, __m=std::memory_order_seq_cst) at /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/atomic_base.h:481
https://github.com/facebook/rocksdb/issues/2 std::__atomic_base<unsigned long>::operator unsigned long (this=0x7b74000012f8) at /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/atomic_base.h:341
https://github.com/facebook/rocksdb/issues/3 0x00000000005bf001 in rocksdb::SeqAdvanceConcurrentTest_SeqAdvanceConcurrent_Test::TestBody()::$_9::operator()(void*) const (this=0x7b14000085e8) at utilities/transactions/write_prepared_transaction_test.cc:1702
Thread 6 (Thread 0x7f228421b700 (LWP 481521) "write_prepared_"):
#0 0x000000000052178c in __tsan::MetaMap::GetAndLock(__tsan::ThreadState*, unsigned long, unsigned long, bool, bool) () at ./db/merge_context.h:15
https://github.com/facebook/rocksdb/issues/1 0x00000000004fa48e in __tsan_atomic64_load () at ./db/merge_context.h:15
https://github.com/facebook/rocksdb/issues/2 0x00000000005e5942 in std::__atomic_base<unsigned long>::load (this=0x7b74000012f8, __m=std::memory_order_seq_cst) at /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/atomic_base.h:481
https://github.com/facebook/rocksdb/issues/3 std::__atomic_base<unsigned long>::operator unsigned long (this=0x7b74000012f8) at /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/atomic_base.h:341
https://github.com/facebook/rocksdb/issues/4 0x00000000005bf001 in rocksdb::SeqAdvanceConcurrentTest_SeqAdvanceConcurrent_Test::TestBody()::$_9::operator()(void*) const (this=0x7b14000085e8) at utilities/transactions/write_prepared_transaction_test.cc:1702
```
This is problematic and suspicious. Two threads will get stuck in the same place trying to load from an atomic variable.
https://github.com/facebook/rocksdb/blob/7.8.fb/utilities/transactions/write_prepared_transaction_test.cc#L1694:L1707. Not sure why two threads can reach the same point.
The stack trace shows that there may be a deadlock, since the two threads are on the same write thread (one is doing Prepare, while the other is trying to commit).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10909
Test Plan:
On CircleCI mini-tsan, apply a patch first so that we have a higher chance of hitting the same problematic situation,
```
diff --git a/utilities/transactions/write_prepared_transaction_test.cc b/utilities/transactions/write_prepared_transaction_test.cc
index 4bc1f3744..bd5dc4924 100644
--- a/utilities/transactions/write_prepared_transaction_test.cc
+++ b/utilities/transactions/write_prepared_transaction_test.cc
@@ -1714,13 +1714,13 @@ TEST_P(SeqAdvanceConcurrentTest, SeqAdvanceConcurrent) {
size_t d = (n % base[bi + 1]) / base[bi];
switch (d) {
case 0:
- threads.emplace_back(txn_t0, bi);
+ threads.emplace_back(txn_t3, bi);
break;
case 1:
- threads.emplace_back(txn_t1, bi);
+ threads.emplace_back(txn_t3, bi);
break;
case 2:
- threads.emplace_back(txn_t2, bi);
+ threads.emplace_back(txn_t3, bi);
break;
case 3:
threads.emplace_back(txn_t3, bi);
```
then build and run tests
```
COMPILE_WITH_TSAN=1 CC=clang-13 CXX=clang++-13 ROCKSDB_DISABLE_ALIGNED_NEW=1 USE_CLANG=1 make V=1 -j32 check
gtest-parallel -r 100 ./write_prepared_transaction_test --gtest_filter=TwoWriteQueues/SeqAdvanceConcurrentTest.SeqAdvanceConcurrent/19
```
In the above, `SeqAdvanceConcurrent/19`. The tests 10 to 19 correspond to unordered write in which Prepare() and Commit() can both enter the same write thread.
Before this PR, there is a high chance of hitting the deadlock. With this PR, no deadlock has been encountered so far.
Reviewed By: ltamasi
Differential Revision: D40869387
Pulled By: riversand963
fbshipit-source-id: 81e82a70c263e4f3417597a201b081ee54f1deab
Yanqin Jin