A spin lock acquire$()$ can be implemented with a test$-$and$-$set instruction as follows:

while $($test$-$and$-$set$($&lock$->$held$)==1)$

; $//$ spin

Recall that test$-$and$-$set$()$returns the old value at the address while atomically setting it to $1.$ Now a

new lock acquire$()$ is implemented as follows:

$1$: while $(1)\{$

$2$: while $($lock$->$held $>0)$

$3$: ; $//$ spin

$4$: if $($test$-$and$-$set$($&lock$->$held$)==0)$

$5$: return;

$6$: $\}$

i$).$ Does it work? Ho