Write a C program to simulate the description below using semaphores to synchronize the processes/threads. A group of fraternity brother and sorority sisters is having a party and drinking from a large communal keg that can hold N servings of soda. When a partier wants to drink, he or she fills a cup from keg, unless it is empty. If the keg is empty, the partier wakes up the pledge and then waits until the pledge has returned with a new keg. Solution #include #include #include #include #include #include #include #define MAX 10 //Keg which holds no of servings int N = MAX; int brothers,sisters,i=0; int Bservings,Sservings; void pledge(int signo); int main() { int pidb,pids; signal( SIGUSR1, pledge ); //instal signal handler //for semaphore declaration int sem_id,j; /* semid of semaphore set */ key_t key = 1234; /* key to pass to semget() */ int nsems = 1; /* nsems to pass to semget() */ //for semaphore operation struct sembuf sop; sem_id=semget(key,nsems,IPC_CREAT|0666); printf(\"No of brothers = \"); scanf(\"%d\",&brothers); printf(\"No of sisters = \"); scanf(\"%d\",&sisters); //create no of brothers while(brothers) { pidb = fork(); if( pidb > 0 ) { printf(\"Parent process\ \"); sop.sem_num = 0; sop.sem_op = -1; sop.sem_flg = 0; if (semop(sem_id, &sop, 1)) { perror(\"Could not increment semaphore\"); exit(5); } kill(getpid(),SIGUSR1); for(j=0; j=0 && Bservings<= N) { ++Bservings; N-=Bservings; printf(\"N = %d\ \",N); printf(\"Servings = %d\ \",Bservings); printf(\"Brother%d has taken %d servings\ \",i,Bservings); } else { printf(\"Brorhes else\ \"); kill(getpid(),SIGUSR1); sop.sem_num = 0; sop.sem_op = -1; sop.sem_flg = 0; if (semop(sem_id, &sop, 1)) { perror(\"Could not increment semaphore\"); exit(5); } } } --brothers; } //create no of brothers i = 0; while(sisters) { pids = fork(); if( pidb > 0 ) { printf(\"Parent process\ \"); for(j=0; j=0 && Sservings<= N) { ++Sservings; N-=Sservings; printf(\"N = %d\ \",N); printf(\"Servings = %d\ \",Sservings); printf(\"Brother%d has taken %d servings\ \",i,Sservings); } else { printf(\"sisters else\ \"); kill(getpid(),SIGUSR1); sop.sem_num = 0; sop.sem_op = -1; sop.sem_flg = 0; if (semop(sem_id, &sop, 1)) { perror(\"Could not increment semaphore\"); exit(5); } } } --sisters; } } //if empty execute pledge void pledge(int signo) { //for semaphore operation struct sembuf sop; int sem_id; /* semid of semaphore set */ key_t key = 1234; /* key to pass to semget() */ int nsems = 1; /* nsems to pass to semget() */ sem_id=semget(key,nsems,0666); if (signo == SIGUSR1) printf(\"received SIGUSR1\ \"); else if (signo == SIGKILL) printf(\"received SIGKILL\ \"); else if (signo == SIGSTOP) printf(\"received SIGSTOP\ \"); //set keg to new value N = MAX; sop.sem_num = 0; sop.sem_op = 1; sop.sem_flg = 0; if (semop(sem_id, &sop, 1)) { perror(\"Could not increment semaphore\"); exit(5); } printf(\"Exiting pledge after setting keg to MAX value\"); }.

1. Write a C program to simulate the description below using semaphores to synchronize the
processes/threads.
A group of fraternity brother and sorority sisters is having a party and drinking from a large
communal keg that can hold N servings of soda. When a partier wants to drink, he or she fills a
cup from keg, unless it is empty. If the keg is empty, the partier wakes up the pledge and then
waits until the pledge has returned with a new keg.
Solution
#include
#include
#include
#include
#include
#include
#include
#define MAX 10
//Keg which holds no of servings
int N = MAX;
int brothers,sisters,i=0;
int Bservings,Sservings;
void pledge(int signo);
int main()
{
int pidb,pids;
signal( SIGUSR1, pledge ); //instal signal handler
//for semaphore declaration
int sem_id,j; /* semid of semaphore set */
key_t key = 1234; /* key to pass to semget() */
int nsems = 1; /* nsems to pass to semget() */
//for semaphore operation
struct sembuf sop;
sem_id=semget(key,nsems,IPC_CREAT|0666);

2. printf("No of brothers = ");
scanf("%d",&brothers);
printf("No of sisters = ");
scanf("%d",&sisters);
//create no of brothers
while(brothers)
{
pidb = fork();
if( pidb > 0 )
{
printf("Parent process ");
sop.sem_num = 0;
sop.sem_op = -1;
sop.sem_flg = 0;
if (semop(sem_id, &sop, 1))
{
perror("Could not increment semaphore");
exit(5);
}
kill(getpid(),SIGUSR1);
for(j=0; j=0 && Bservings<= N)
{
++Bservings;
N-=Bservings;
printf("N = %d ",N);
printf("Servings = %d ",Bservings);
printf("Brother%d has taken %d servings ",i,Bservings);
}
else
{
printf("Brorhes else ");
kill(getpid(),SIGUSR1);
sop.sem_num = 0;
sop.sem_op = -1;
sop.sem_flg = 0;
if (semop(sem_id, &sop, 1))

3. {
perror("Could not increment semaphore");
exit(5);
}
}
}
--brothers;
}
//create no of brothers
i = 0;
while(sisters)
{
pids = fork();
if( pidb > 0 )
{
printf("Parent process ");
for(j=0; j=0 && Sservings<= N)
{
++Sservings;
N-=Sservings;
printf("N = %d ",N);
printf("Servings = %d ",Sservings);
printf("Brother%d has taken %d servings ",i,Sservings);
}
else
{
printf("sisters else ");
kill(getpid(),SIGUSR1);
sop.sem_num = 0;
sop.sem_op = -1;
sop.sem_flg = 0;
if (semop(sem_id, &sop, 1))
{
perror("Could not increment semaphore");
exit(5);

4. }
}
}
--sisters;
}
}
//if empty execute pledge
void pledge(int signo)
{
//for semaphore operation
struct sembuf sop;
int sem_id; /* semid of semaphore set */
key_t key = 1234; /* key to pass to semget() */
int nsems = 1; /* nsems to pass to semget() */
sem_id=semget(key,nsems,0666);
if (signo == SIGUSR1)
printf("received SIGUSR1 ");
else if (signo == SIGKILL)
printf("received SIGKILL ");
else if (signo == SIGSTOP)
printf("received SIGSTOP ");
//set keg to new value
N = MAX;
sop.sem_num = 0;
sop.sem_op = 1;
sop.sem_flg = 0;
if (semop(sem_id, &sop, 1))
{
perror("Could not increment semaphore");
exit(5);
}
printf("Exiting pledge after setting keg to MAX value");
}