atomic memory operation
A RISC-V instruction that does a whole atomic update in one step, such as amoadd.w, which adds to memory and returns the old value.
RISC-V's A extension provides AMOs (amoswap, amoadd, amoand, amoor, amoxor, amomin/max[u]) in .w and .d forms with optional .aq/.rl ordering bits, alongside lr/sc; Zacas adds amocas.