Notes

LAB 6-7

Ques 4

pthread_create() for thread 1 returns: 0 Thread 1 pthread_create() for thread 2 returns: 0 Thread 2



Ques 5

Thread number 140542581389056

Thread number 140542547830528

Thread number 140542514272000

Thread number 140542480713472

Thread number 140542447154944

Thread number 140542413596416

Thread number 140542380037888

Thread number 140542312920832

Thread number 140542346479360

Thread number 140542279362304

Final counter value: 10



Thread 1: Exiting critical region...



Ques 6

#include<stdio.h>

#include<semaphore.h>

#include<pthread.h>

#include<stdlib.h>

#define buffersize 10

pthread_mutex_t mutex;

pthread_t tidP,tidC;

sem_t full,empty;

int counter;

int buffer[buffersize];



void initialize()

{

pthread_mutex_init(&mutex,NULL);

sem_init(&full,1,0);

sem_init(&empty,1,buffersize);

counter=0;

}



void write(int item)

{

buffer[counter++]=item;

}



int read()

{

return(buffer[--counter]);

}



void * producer (void * param)

{

int waittime,item,i;

item=rand()%5;

waittime=rand()%5;

sem_wait(&empty);

pthread_mutex_lock(&mutex);

printf("nProducer has produced item: %dn",item);

write(item);

pthread_mutex_unlock(&mutex);

sem_post(&full);

}



void * consumer (void * param)

{

int waittime,item;

waittime=rand()%5;

sem_wait(&full);

pthread_mutex_lock(&mutex);

item=read();

printf("nConsumer has consumed item: %dn",item);

pthread_mutex_unlock(&mutex);

sem_post(&empty);

}



int main()

{

int n1,n2,i;

initialize();



pthread_create(&tidP,NULL,producer,NULL);



pthread_create(&tidC,NULL,consumer,NULL);



pthread_join(tidP,NULL);



pthread_join(tidC,NULL);



//sleep(5);

exit(0);

}



Ques 7

#include<stdio.h>

#include<pthread.h>

#include<semaphore.h>



sem_t mutex;

sem_t db;

int readercount=0;

pthread_t reader1,reader2,writer1,writer2;

void *reader(void *);

void *writer(void *);

void main()

{

sem_init(&mutex,0,1);

sem_init(&db,0,1);

int i=1;

while(i<=3)

{

pthread_create(&reader1,NULL,reader,"1");

pthread_create(&reader2,NULL,reader,"2");

pthread_create(&writer1,NULL,writer,"1");

pthread_join(reader1,NULL);

pthread_join(reader2,NULL);

pthread_join(writer1,NULL);

i++;



}





}

void *reader(void *p)

{

printf("prevoius value %dn",mutex);

sem_wait(&mutex);

printf("Mutex acquired by reader %dn",mutex);

readercount++;

if(readercount==1) sem_wait(&db);

sem_post(&mutex);

printf("Mutex returned by reader %dn",mutex);

printf("Reader %s is Readingn",p);

//sleep(3);

sem_wait(&mutex);

printf("Reader %s Completed Readingn",p);

readercount--;

if(readercount==0) sem_post(&db);

sem_post(&mutex);

}



void *writer(void *p)

{

printf("Writer is Waiting n");

sem_wait(&db);

printf("Writer %s is writingn ",p);

sem_post(&db);

//sleep(2);

}