Memory ordering needs justification

When using atomic operations, explicitly justify the choice of memory ordering. Each use of a memory ordering should be documented with a clear explanation of why that specific ordering is sufficient and safe.

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When using atomic operations, explicitly justify the choice of memory ordering. Each use of a memory ordering should be documented with a clear explanation of why that specific ordering is sufficient and safe.

Key guidelines:

  • Use Relaxed for simple counters without synchronization needs
  • Use Acquire/Release for establishing happens-before relationships
  • Avoid mixing SeqCst with other orderings
  • Document safety assumptions for weaker orderings

Example:

impl<T> Clone for Sender<T> {
    fn clone(&self) -> Self {
        // Relaxed is sufficient for incrementing the reference count
        // since no synchronization is needed - the sender is already
        // guaranteed to be valid when Clone is called
        self.shared.ref_count.fetch_add(1, Relaxed);
        Self { shared: self.shared.clone() }
    }
}

impl<T> Drop for Sender<T> {
    fn drop(&mut self) {
        // AcqRel ordering required for reference count decrement
        // to synchronize with other threads that may be checking
        // if this is the last sender
        if self.shared.ref_count.fetch_sub(1, AcqRel) == 1 {
            self.shared.close();
        }
    }
}

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