Re: Arm ldaxr / stxr loop question

On Mon, 28 Oct 2024 15:13:03 -0400, jseigh wrote:

So if were to implement a spinlock using the above instructions
something along the lines of
>
.L0
  ldaxr    -- load lockword exclusive w/ acquire membar
  cmp      -- compare to zero
  bne  .LO -- loop if currently locked
         stxr     -- store 1
         cbnz .LO -- retry if stxr failed

The closest I could find to this was on page 8367
of DDI0487G_a_armv8_arm.pdf from infocenter.arm.com:

    Loop
        LDAXR W5, [X1]       ; read lock with acquire
        CBNZ W5, Loop        ; check if 0
        STXR W5, W0, [X1]    ; attempt to store new value
        CBNZ W5, Loop        ; test if store succeeded and retry if not