#include

#include "common$\_$threads.h$"$

int done $=0$;

void$*$ worker$($void$*$ arg$)\{$

$$ printf$("$this should print first

$")$;

$$ done $=1$;

$$ return NULL;

$\}$

int main$($int argc, char $*$argv$[])\{$

$$ pthread$\_$t p;

$$ Pthread$\_$create$($&p$,$ NULL, worker, NULL$)$;

$$ while $($done $==0)$

$$ ;

$$ printf$("$this should print last

$")$;

$$ return $0$;

$\}$

What synchronized primitives can be added to above program to make the mutual exclusion effectively and effeciently $?$ Choose all options suitable.

Add join$()$ in the main$()$ thread to force it to wait for the completion of the worker thread.

Add a lock surrounding the global variable 'done' in both main$()$ and worker thread for controlled access.

Add condition varaiable to coordinate the action between main$()$ thread and worker thread. Specifically, add wait$()$ inside the while loop in the main$()$ to suspend the its execution until the worker thread completes the change on the global variable and notifies the main$()$ by invoking signal$().$

Change the while $($done $==0)$ to if $($done $==0)$ to stop the spin waiting of main thread. This avoid wasting the CPU cycle.