Should I Use Recursive Locking in Go, and What's a Better Alternative?

Understanding Recursive Locking in Go: Avoiding the Pitfalls

While Go's sync package provides a Mutex mechanism, it lacks support for recursive locking. This article explores the reasons for this deficiency and presents a more suitable approach to handling recursive scenarios.

The Drawbacks of Recursive Locks

According to Russ Cox, a member of the Go development team, recursive mutexes are considered flawed for several reasons. Firstly, they undermine the core purpose of mutexes, which is to protect invariants and assert their validity. Recursive locking renders these invariants unreliable, leading to potential errors.

Secondly, recursive locks can mask debugging difficulties. For instance, if a function calls another function that requires a lock, it may never catch the error in single-threaded testing, as the lock is never explicitly acquired within the calling function.

A Recommended Alternative

Instead of relying on recursive locks, it's advisable to redesign your code to eliminate the need for them. If you encounter scenarios where a function must be callable with or without a mutex, the preferred approach is to create two separate versions:

• One version (e.g., g()) to be called with the mutex already in possession, requiring the caller to ensure specific safeguards are met.
• Another version (e.g., G()) that explicitly acquires the mutex before calling the internal function.

This разделение allows for a clear delineation of responsibilities and prevents potential issues related to invariant protection and debugging.

Conclusion

While recursive locking may appear tempting in certain situations, it is ultimately a flawed approach in Go. By embracing a careful redesign of your code, you can avoid the pitfalls associated with recursive locks and ensure the integrity of your software's functionality.

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