33.10.3.1.3. ARMv8 spinlock pattern
sev 1: wfe 2: ldaxr w1, [w0] cbnz w1, %1b stxr w1, w2, [w0] cbnz w1, %2b
It is the STXR from the unlock on another core that automatically wakes up the spinlock afterwards: https://stackoverflow.com/questions/32276313/how-is-a-spin-lock-woken-up-in-linux-arm64