$3.(7$ points$)$

$($a$)$ Given the following program in which two threads concurrently update one critical resource shared$\_$data without using lock$($s$).$ Theoretically, how many different final values may shared$\_$data have? Please explain how each different value is attained by giving the running order of the statements $($e$.$g$.,9,10,11)$ of the two threads.

$```$

$\backslash$l

$\backslash$l

$|$

shared$\_$data $=1$

rlock $=$ threading.RLock$()$

def test$(2)$:

global shared$\_$data

for in in range$($r$)$; ; lock.aq uirell

rlockqqunt local $=$ shared$\_$data rlock, relone

Mrkreloselocal $=$ local $2$

shared$\_$data $=$ local

time.sleep$(1)$ rlock, reqease

t$1=$ threading.Thread$($target $=$ test, args $=(2,))$

t$2=$ threading.Thread$($target $=$ test, args $=(2,))$

t$1.$start$()$

t$2.$start$()$

t$1.$join$()$

t$2.$join$()$

print$($shared$\_$data$)$

$```$

Theoretical Val. of shaved$-$data