1. `StorageEngine::_delete_tablets_on_unused_root_path` will try to obtain tablet shard write lock in `TabletManager`
```
StorageEngine::_delete_tablets_on_unused_root_path
TabletManager::drop_tablets_on_error_root_path
obtain each tablet shard's write lock
```
2. `TabletManager::build_all_report_tablets_info` and other methods will obtain tablet shard read lock frequently.
So, `StorageEngine::_delete_tablets_on_unused_root_path` will hold `_store_lock` for a long time.
This will make it difficult for other threads to get write `_store_lock`, such as `StorageEngine::get_stores_for_create_tablet`
`drop_tablets_on_error_root_path` is a small probability event, `TabletManager::drop_tablets_on_error_root_path` should return when its param `tablet_info_vec` is empty
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