Lock-based concurrent data structures
Lock-based concurrent data structures are a type of concurrent structure. They are called lock-based because they use synchronization-locking mechanisms such as mutexes to ensure that only one thread can access the underlying data.
A thread-safe singleton pattern
In the previous chapter, we discussed deadlocks and ways to avoid them. The last example we used was implementing a thread-safe singleton pattern. We will expand on that in this section. Imagine that we want to use a class for creating database connections. We will name that class connection_manager.
Here’s a simple pattern implementation that tracks down the connections to the database. Keeping a separate connection whenever we need access to the database is not a good practice. Instead, we will re-use the existing connection to query the database from different parts of the program:
#include <memory>namespace db_utils {
class connection_manager {
private:
 ...
