Fix race condition in db_stress thread setup (#9314)

Summary:
We need to grab `SharedState`'s mutex while calling `IncThreads()` or `IncBgThreads()`. Otherwise the newly launched threads can simultaneously access the thread counters to check if every thread has finished initializing.

Repro command:

```
$ rm -rf /dev/shm/rocksdb/rocksdb_crashtest_{whitebox,expected}/ && mkdir -p /dev/shm/rocksdb/rocksdb_crashtest_{whitebox,expected}/ && ./db_stress --acquire_snapshot_one_in=10000 --atomic_flush=1 --avoid_flush_during_recovery=0 --avoid_unnecessary_blocking_io=1 --backup_max_size=104857600 --backup_one_in=100000 --batch_protection_bytes_per_key=0 --block_size=16384 --bloom_bits=131.8094496796033 --bottommost_compression_type=zlib --cache_index_and_filter_blocks=1 --cache_size=1048576 --checkpoint_one_in=1000000 --checksum_type=kCRC32c --clear_column_family_one_in=0 --compact_files_one_in=1000000 --compact_range_one_in=1000000 --compaction_style=1 --compaction_ttl=0 --compression_max_dict_buffer_bytes=134217727 --compression_max_dict_bytes=16384 --compression_parallel_threads=1 --compression_type=zstd --compression_zstd_max_train_bytes=65536 --continuous_verification_interval=0 --db=/dev/shm/rocksdb/rocksdb_crashtest_whitebox --db_write_buffer_size=8388608 --delpercent=5 --delrangepercent=0 --destroy_db_initially=0 --disable_wal=1 --enable_compaction_filter=0 --enable_pipelined_write=0 --fail_if_options_file_error=1 --file_checksum_impl=crc32c --flush_one_in=1000000 --format_version=5 --get_current_wal_file_one_in=0 --get_live_files_one_in=1000000 --get_property_one_in=1000000 --get_sorted_wal_files_one_in=0 --index_block_restart_interval=15 --index_type=3 --iterpercent=10 --key_len_percent_dist=1,30,69 --level_compaction_dynamic_level_bytes=True --log2_keys_per_lock=22 --long_running_snapshots=0 --mark_for_compaction_one_file_in=10 --max_background_compactions=20 --max_bytes_for_level_base=10485760 --max_key=1000000 --max_key_len=3 --max_manifest_file_size=1073741824 --max_write_batch_group_size_bytes=1048576 --max_write_buffer_number=3 --max_write_buffer_size_to_maintain=4194304 --memtablerep=skip_list --mmap_read=1 --mock_direct_io=False --nooverwritepercent=1 --open_files=500000 --open_metadata_write_fault_one_in=0 --open_read_fault_one_in=32 --open_write_fault_one_in=0 --ops_per_thread=20000 --optimize_filters_for_memory=1 --paranoid_file_checks=0 --partition_filters=0 --partition_pinning=0 --pause_background_one_in=1000000 --periodic_compaction_seconds=0 --prefixpercent=5 --prepopulate_block_cache=1 --progress_reports=0 --read_fault_one_in=1000 --readpercent=45 --recycle_log_file_num=1 --reopen=0 --ribbon_starting_level=999 --secondary_cache_fault_one_in=32 --snapshot_hold_ops=100000 --sst_file_manager_bytes_per_sec=104857600 --sst_file_manager_bytes_per_truncate=1048576 --subcompactions=2 --sync=0 --sync_fault_injection=False --target_file_size_base=2097152 --target_file_size_multiplier=2 --test_batches_snapshots=1 --test_cf_consistency=1 --top_level_index_pinning=0 --unpartitioned_pinning=0 --use_block_based_filter=1 --use_clock_cache=0 --use_direct_io_for_flush_and_compaction=0 --use_direct_reads=0 --use_full_merge_v1=1 --use_merge=0 --use_multiget=1 --user_timestamp_size=0 --verify_checksum=1 --verify_checksum_one_in=1000000 --verify_db_one_in=100000 --write_buffer_size=1048576 --write_dbid_to_manifest=1 --write_fault_one_in=0 --writepercent=35
```

TSAN error:

```
WARNING: ThreadSanitizer: data race (pid=2750142)
  Read of size 4 at 0x7ffc21d7f58c by thread T39 (mutexes: write M670895590377780496):
    #0 rocksdb::SharedState::AllInitialized() const db_stress_tool/db_stress_shared_state.h:204 (db_stress+0x4fd307)
    https://github.com/facebook/rocksdb/issues/1 rocksdb::ThreadBody(void*) db_stress_tool/db_stress_driver.cc:26 (db_stress+0x4fd307)
    https://github.com/facebook/rocksdb/issues/2 StartThreadWrapper env/env_posix.cc:454 (db_stress+0x84472f)

  Previous write of size 4 at 0x7ffc21d7f58c by main thread:
    #0 rocksdb::SharedState::IncThreads() db_stress_tool/db_stress_shared_state.h:194 (db_stress+0x4fd779)
    https://github.com/facebook/rocksdb/issues/1 rocksdb::RunStressTest(rocksdb::StressTest*) db_stress_tool/db_stress_driver.cc:78 (db_stress+0x4fd779)
    https://github.com/facebook/rocksdb/issues/2 rocksdb::db_stress_tool(int, char**) db_stress_tool/db_stress_tool.cc:348 (db_stress+0x4b97dc)
    https://github.com/facebook/rocksdb/issues/3 main db_stress_tool/db_stress.cc:21 (db_stress+0x47a351)

  Location is stack of main thread.

  Location is global '<null>' at 0x000000000000 ([stack]+0x00000001d58c)

  Mutex M670895590377780496 is already destroyed.

  Thread T39 (tid=2750211, running) created by main thread at:
    #0 pthread_create /home/engshare/third-party2/gcc/9.x/src/gcc-10.x/libsanitizer/tsan/tsan_interceptors.cc:964 (libtsan.so.0+0x613c3)
    https://github.com/facebook/rocksdb/issues/1 StartThread env/env_posix.cc:464 (db_stress+0x8463c2)
    https://github.com/facebook/rocksdb/issues/2 rocksdb::CompositeEnvWrapper::StartThread(void (*)(void*), void*) env/composite_env_wrapper.h:288 (db_stress+0x4bcd20)
    https://github.com/facebook/rocksdb/issues/3 rocksdb::EnvWrapper::StartThread(void (*)(void*), void*) include/rocksdb/env.h:1475 (db_stress+0x4bb950)
    https://github.com/facebook/rocksdb/issues/4 rocksdb::RunStressTest(rocksdb::StressTest*) db_stress_tool/db_stress_driver.cc:80 (db_stress+0x4fd9d2)
    https://github.com/facebook/rocksdb/issues/5 rocksdb::db_stress_tool(int, char**) db_stress_tool/db_stress_tool.cc:348 (db_stress+0x4b97dc)
    https://github.com/facebook/rocksdb/issues/6 main db_stress_tool/db_stress.cc:21 (db_stress+0x47a351)

 ThreadSanitizer: data race db_stress_tool/db_stress_shared_state.h:204 in rocksdb::SharedState::AllInitialized() const
```

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9314

Test Plan: verified repro command works after this PR.

Reviewed By: jay-zhuang

Differential Revision: D33217698

Pulled By: ajkr

fbshipit-source-id: 79358fe5adb779fc9dcf80643cc102d4b467fc38

db_stress_tool/db_stress_driver.cc

@@ -69,27 +69,31 @@ bool RunStressTest(StressTest* stress) {
 #endif
 
   uint32_t n = FLAGS_threads;
-
   uint64_t now = clock->NowMicros();
   fprintf(stdout, "%s Initializing worker threads\n",
           clock->TimeToString(now / 1000000).c_str());
+
+  ThreadState bg_thread(0, &shared);
+  ThreadState continuous_verification_thread(0, &shared);
   std::vector<ThreadState*> threads(n);
+  {
+    MutexLock l(shared.GetMutex());
+
     for (uint32_t i = 0; i < n; i++) {
       shared.IncThreads();
       threads[i] = new ThreadState(i, &shared);
       db_stress_env->StartThread(ThreadBody, threads[i]);
     }
-  ThreadState bg_thread(0, &shared);
     if (FLAGS_compaction_thread_pool_adjust_interval > 0) {
       shared.IncBgThreads();
       db_stress_env->StartThread(PoolSizeChangeThread, &bg_thread);
     }
-  ThreadState continuous_verification_thread(0, &shared);
     if (FLAGS_continuous_verification_interval > 0) {
       shared.IncBgThreads();
       db_stress_env->StartThread(DbVerificationThread,
                                  &continuous_verification_thread);
     }
+  }
 
   // Each thread goes through the following states:
   // initializing -> wait for others to init -> read/populate/depopulate