[bheadmaster]

On ARM systems with LSE both weak and strong compile to the same CAS instruction anyway. On LL/SC, using strong means CPU will attempt to retry the same exchange on spurious failure, which increases likelihood that another thread will update the value in the meantime, requiring an outer loop retry.

On any plaform which implements strong exchange with zero overhead over weak exchange, we can safely assume they compile to the same thing, and use weak. The only reason to use `strong` is if you have a one-shot CAS operation and you don't want to write a retry loop.