• Move the timeout == 0 guard outside the else so a non-blocking call returns immediately after a failed CAS instead of entering the spin loop.
• Reload v on every spin iteration, allowing timed/blocking callers to notice an unlock promptly.

No-GIL builds now honor the semantics of non-blocking attempts and avoid wasted CPU; GIL builds are unaffected (MAX_SPIN_COUNT == 0).

• Issue: Non-blocking _PyMutex_LockTimed spins and may fail unnecessarily in no-GIL builds #135871