Lock-free Atomic Shared Pointers Without a Split Reference Count? It Can Be Done! - Daniel Anderson

Learn how to create lock-free atomic shared pointers without a split reference count, a key innovation in modern concurrency techniques, with a deep dive into the benefits and challenges of this approach.

Key takeaways

A shared pointer without a split reference count is not thread-safe.
The main problem is solving the use-after-free issue when deleting a shared pointer.
To avoid this, consider using the split reference count technique, which adds a local reference count for the shared pointer.
Lock-free atomic shared pointers are possible without using locks.
The key idea is to use a local reference count for the shared pointer, which is incremented and decremented atomically.
The local reference count is used to protect the control block and prevent use-after-free issues.
The control block is only deleted when the local reference count reaches zero.
Deferred reclamation can be used to implement the split reference count technique.
The technique is already used in some production libraries, such as Folly.
Other techniques, like hazard pointers, can also be used to solve the use-after-free issue.
The technique is not without its challenges, such as dealing with cache effects and aliasing.

Lock-free Atomic Shared Pointers Without a Split Reference Count? It Can Be Done! - Daniel Anderson

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