Constant NO_CROSS_PROCESS_LOCK_GENERATION 

pub const NO_CROSS_PROCESS_LOCK_GENERATION: u64 = 0; // 0u64

Sentinel value representing the absence of a lock generation value.

When the lock is created, it has no generation. Once locked, it receives its first generation from TryLock::try_lock. Subsequent lockings may generate new lock generation. The generation is incremented by 1 every time.

The first generation is defined by FIRST_CROSS_PROCESS_LOCK_GENERATION.