Add missing mutex when reading from shared variable bg_bottom_compaction_scheduled_, bg_compaction_scheduled_ (#10610)

Summary:
**Context/Summary:**
According to https://github.com/facebook/rocksdb/blob/7.6.fb/db/compaction/compaction_job.h#L328-L332, any reading in the form of `*bg_compaction_scheduled_` , `*bg_bottom_compaction_scheduled_` should be protected by mutex, which isn't the case for some assert statement. This leads to a data race that can be repro-ed by the following command (command coming soon)

```
db=/dev/shm/rocksdb_crashtest_blackbox
exp=/dev/shm/rocksdb_crashtest_expected
rm -rf $db $exp
mkdir -p $exp

./db_stress --clear_column_family_one_in=0 --column_families=1 --db=$db --delpercent=10 --delrangepercent=0 --destroy_db_initially=1 --expected_values_dir=$exp --iterpercent=0 --key_len_percent_dist=1,30,69 --max_key=1000000 --max_key_len=3 --prefixpercent=0 --readpercent=0 --reopen=0 --ops_per_thread=100000000 --value_size_mult=32 --writepercent=90  --compaction_pri=4 --use_txn=1 --level_compaction_dynamic_level_bytes=True  --compaction_ttl=0  --compact_files_one_in=1000000 --compact_range_one_in=1000000 --value_size_mult=32 --verify_db_one_in=1000  --write_buffer_size=65536 --mark_for_compaction_one_file_in=10 --max_background_compactions=20 --max_key=25000000 --max_key_len=3 --max_write_buffer_number=3 --max_write_buffer_size_to_maintain=2097152 --target_file_size_base=2097152 --target_file_size_multiplier=2
```
```
WARNING: ThreadSanitizer: data race (pid=73424)
  Read of size 4 at 0x7b8c0000151c by thread T13:
    #0 ReleaseSubcompactionResources internal_repo_rocksdb/repo/db/compaction/compaction_job.cc:390 (db_stress+0x630aa3)
    https://github.com/facebook/rocksdb/issues/1 rocksdb::CompactionJob::Run() internal_repo_rocksdb/repo/db/compaction/compaction_job.cc:741 (db_stress+0x630aa3)
    https://github.com/facebook/rocksdb/issues/2 rocksdb::DBImpl::BackgroundCompaction(bool*, rocksdb::JobContext*, rocksdb::LogBuffer*, rocksdb::DBImpl::PrepickedCompaction*, rocksdb::Env::Priority) internal_repo_rocksdb/repo/db/db_impl/db_impl_compaction_flush.cc:3436 (db_stress+0x60b2cc)
    https://github.com/facebook/rocksdb/issues/3 rocksdb::DBImpl::BackgroundCallCompaction(rocksdb::DBImpl::PrepickedCompaction*, rocksdb::Env::Priority) internal_repo_rocksdb/repo/db/db_impl/db_impl_compaction_flush.cc:2950 (db_stress+0x606d79)
    https://github.com/facebook/rocksdb/issues/4 rocksdb::DBImpl::BGWorkCompaction(void*) internal_repo_rocksdb/repo/db/db_impl/db_impl_compaction_flush.cc:2693 (db_stress+0x60356a)

  Previous write of size 4 at 0x7b8c0000151c by thread T12 (mutexes: write M438955329917552448):
    #0 rocksdb::DBImpl::BackgroundCallCompaction(rocksdb::DBImpl::PrepickedCompaction*, rocksdb::Env::Priority) internal_repo_rocksdb/repo/db/db_impl/db_impl_compaction_flush.cc:3018 (db_stress+0x6072a1)
    https://github.com/facebook/rocksdb/issues/1 rocksdb::DBImpl::BGWorkCompaction(void*) internal_repo_rocksdb/repo/db/db_impl/db_impl_compaction_flush.cc:2693 (db_stress+0x60356a)

Location is heap block of size 6720 at 0x7b8c00000000 allocated by main thread:
    #0 operator new(unsigned long, std::align_val_t) <null> (db_stress+0xbab5bb)
    https://github.com/facebook/rocksdb/issues/1 rocksdb::DBImpl::Open(rocksdb::DBOptions const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::vector<rocksdb::ColumnFamilyDescriptor, std::allocator<rocksdb::ColumnFamilyDescriptor> > const&, std::vector<rocksdb::ColumnFamilyHandle*, std::allocator<rocksdb::ColumnFamilyHandle*> >*, rocksdb::DB**, bool, bool) internal_repo_rocksdb/repo/db/db_impl/db_impl_open.cc:1811 (db_stress+0x69769a)
    https://github.com/facebook/rocksdb/issues/2 rocksdb::TransactionDB::Open(rocksdb::DBOptions const&, rocksdb::TransactionDBOptions const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::vector<rocksdb::ColumnFamilyDescriptor, std::allocator<rocksdb::ColumnFamilyDescriptor> > const&, std::vector<rocksdb::ColumnFamilyHandle*, std::allocator<rocksdb::ColumnFamilyHandle*> >*, rocksdb::TransactionDB**) internal_repo_rocksdb/repo/utilities/transactions/pessimistic_transaction_db.cc:258 (db_stress+0x8ae1f4)
    https://github.com/facebook/rocksdb/issues/3 rocksdb::StressTest::Open(rocksdb::SharedState*) internal_repo_rocksdb/repo/db_stress_tool/db_stress_test_base.cc:2611 (db_stress+0x32b927)
    https://github.com/facebook/rocksdb/issues/4 rocksdb::StressTest::InitDb(rocksdb::SharedState*) internal_repo_rocksdb/repo/db_stress_tool/db_stress_test_base.cc:290 (db_stress+0x34712c)
```
This PR added all the missing mutex that should've been in place

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10610

Test Plan:
- Past repro command
- Existing CI

Reviewed By: riversand963

Differential Revision: D39143016

Pulled By: hx235

fbshipit-source-id: 51dd4db55ad306f3dbda5d0dd54d6f2513cf70f2

db/compaction/compaction_job.cc

@@ -321,6 +321,7 @@ void CompactionJob::AcquireSubcompactionResources(
               ->write_controller()
               ->NeedSpeedupCompaction())
           .max_compactions;
+  InstrumentedMutexLock l(db_mutex_);
   // Apply min function first since We need to compute the extra subcompaction
   // against compaction limits. And then try to reserve threads for extra
   // subcompactions. The actual number of reserved threads could be less than
@@ -329,7 +330,6 @@ void CompactionJob::AcquireSubcompactionResources(
       std::max(max_db_compactions - *bg_compaction_scheduled_ -
                    *bg_bottom_compaction_scheduled_,
                0);
-  db_mutex_->Lock();
   // Reservation only supports backgrdoun threads of which the priority is
   // between BOTTOM and HIGH. Need to degrade the priority to HIGH if the
   // origin thread_pri_ is higher than that. Similar to ReleaseThreads().
@@ -346,7 +346,6 @@ void CompactionJob::AcquireSubcompactionResources(
   } else {
     *bg_compaction_scheduled_ += extra_num_subcompaction_threads_reserved_;
   }
-  db_mutex_->Unlock();
 }
 
 void CompactionJob::ShrinkSubcompactionResources(uint64_t num_extra_resources) {
@@ -380,6 +379,8 @@ void CompactionJob::ReleaseSubcompactionResources() {
   if (extra_num_subcompaction_threads_reserved_ == 0) {
     return;
   }
+  {
+    InstrumentedMutexLock l(db_mutex_);
     // The number of reserved threads becomes larger than 0 only if the
     // compaction prioity is round robin and there is no sufficient
     // sub-compactions available
@@ -391,6 +392,7 @@ void CompactionJob::ReleaseSubcompactionResources() {
                1 + extra_num_subcompaction_threads_reserved_ ||
            *bg_compaction_scheduled_ >=
                1 + extra_num_subcompaction_threads_reserved_);
+  }
   ShrinkSubcompactionResources(extra_num_subcompaction_threads_reserved_);
 }