Iwo processes PO and P$1$ are trying to enter their critical sections using the shared variable lock $($boolean$)$ and the TestandSetLock instruction. Initially, lock is set to FALSE.

$($i$)$ What is the purpose of TestAndSet$()$ instruction?

$($ii$)$ Now, if both processes P$0$ and P$1$ simultaneously execute TestAndSetLock$($lock$)$ instruction, what happens?

boolean Testandset $($boolean $*$target$)\{$

boolean $rv=**$ target;

$*$target $=$ TRUE;

return rv;

$\}$

Figure $5\mathrm{.}3$ The definition of the TestAndSet $()$ instruction.

do $\{$

while $($TestAndSetLock $($&lock$))$

; $//$ do nothing

$//$ critical section

lock $=$ FALSE;

$//$ remainder section

$\}$while $($TRUE$)$ ;

Figure $5\mathrm{.}4$ Mutual$-$exclusion implementation with TestAndSet $().$