Problem $8.(6$ points$)$:

Processes vs$.$ threads. This problem tests your understanding of the some of the important differences

between processes and threads. Consider the following $C$ program:

#include "csapp.h$"$

int main$()$

$\{$

$/*$ Global variables $*/$

int cnt;

sem$\_$t mutex;

int $i$;

pthread$\_$t tid$[2]$;

sem$\_$init$($&mutex, $0,1)$; $/*$ mutex$=1*/$

$/*$ Helper function $*/$

void $*$incr $($void $*$vargp$)$

$\{$

P $($&mutex$)$ ;

cnt$++$;

$V($&mutex$)$;

return NULL;

$\}$

$/*$ Processes $*/$

$cnt=0$;

for

incr $($NULL$)$ ;

if fork $()==0$

incr $($NULL$)$ ;

exit$(0)$;

$\}$

$\}$

for $(i=0$;$i<mn\; id="EditorElement\_691590">2</mn>$;$i++)$

wait$($NULL$)$ ;

printf$("$Procs: $,$ cnt $=\%\frac{d}{?}$

$,$ cnt$)$ ;

$/*$ Threads $*/$

$cnt=O$;

for

incr $($NULL$)$;

pthread$\_$create$($&tid$[$i$],$ NULL, incr, NULL$)$;

$\}$

for $(i=0$;$i<mn\; id="EditorElement\_691356">2</mn>$;$i++)$

pthread$\_$join$($tid$[$i$],$ NULL$)$ ;

printf$("$Threads: cnt $=\%\frac{d}{?}$

$,cnt$;

exit$(0)$;

$\}$

A$.$ What is the output of this program?

Procs: $,cnt=$

Threads: $c$ nt $=$