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