2. Core Traits

LockPolicy: The Acquisition Strategy

The LockPolicy trait defines the raw mechanics of claiming a resource. It is intentionally minimal and strictly atomic. It includes an associated Meta type, allowing implementations to pass state (like a ticket number or guard token) from the acquisition step (try_lock) to the release step (free).

RetryPolicy: The Waiting Strategy

The RetryPolicy trait defines what the CPU should do when a LockPolicy reports contention. This could be a tight CPU pause loop (retry::Busy), yielding to the OS scheduler (retry::Yield), or even a custom exponential backoff strategy.

SharingPolicy: The Read-Write Semantics

Extends LockPolicy to support shared (reader) access. This allows a single lock primitive to support both reader and writer access, forming the basis for the Sharex (RwLock) primitive.

NewLocked: The Initialization Strategy

Allows locks to be created in an already-acquired (locked) state. This is crucial for primitives like Gate that must start closed to prevent Time-of-Check to Time-of-Use (TOCTOU) races. By segregating this into a separate trait, Resync follows the Interface Segregation Principle.

Mutex & Sharex: The Composition

These structs bind a LockPolicy, a RetryPolicy, and the protected data (T) together, providing a safe, RAII-based interface (ExGuard and ShGuard). They also manage the Lock Poisoning state, automatically detecting thread panics (when std is enabled) to protect data integrity.