PROCESS Semaphore implementation on reader-writer giving brillient synchronizaTion

anubala331

/MY ALL PROGRAMS ARE COMPILED ON FEDORA 15 ..WITH 4.6. gcc comppiler/

**/* WRITER1*/**

//I M REALLY VERY SORY ...semop is not done ...so semaphore is not working...i have corrected it in further program......but still due to way of coding ...project is showing brillient synchronisation...

//REASONS OF BLOCK ON OPEN

//U r trying to open a fifo...which does not exist...not made

//U r opening fifo on one side at WR_ONLY mode...& fifo is not opened at another side at RD_ONLY mode

//then it will go at block on open ...vice versa is also possible reason

//U may open same fifo at O_RDWR mode to not to go in block on open....

#include<stdio.h>

#include<stdlib.h>

#include<fcntl.h>

#include<sys/ipc.h>

#include<unistd.h>

#include<sys/types.h>

#include<sys/sem.h>

struct sembuf a;

int sem_ac(int kid)

{

a.sem_num=0;

a.sem_op=-1;

a.sem_flg=SEM_UNDO;

return 0;

}

int sem_rs(int kid)

{

a.sem_num=0;

a.sem_op=1;

a.sem_flg=SEM_UNDO;

return 0;

}

int main()

{

int kid;

kid=semget(144,1,777|IPC_CREAT);

printf("kid=%d\n",kid);

int ret,wfd,count=0;

int buff=5;

int a=10;

int b=15;

ret=mkfifo("anu",777|IPC_CREAT);

if(ret==0)

printf("fifo created\n");

sem_ac(kid);

wfd=open("anu",O_WRONLY);//after opening ...if it finds a reader...it will write data to fifo untill its limit exceeds ...when limit came...it will allow reader to read ...then again starts wriiting to fifo..

printf("wfd=%d\n",wfd);

count=write(wfd,&buff,4);

printf("count=%d buff=%d\n",count,buff);

//fd=open("anu",O_WRONLY);

//printf("fd=%d\n",fd);

close(wfd);

wfd=open("anu",O_WRONLY);//same reader will works for no. of writers

printf("wfd=%d\n",wfd);

count=write(wfd,&a,4);

printf("count=%d a=%d\n",count,a);

close(wfd);//it will make no diffrence if i opened same fifo after closing....data will remain in that fifo......

wfd=open("anu",O_WRONLY);

printf("wfd=%d\n",wfd);

count=write(wfd,&b,4);

printf("count=%d b=%d\n",count,b);

close(wfd);

//sleep(1);

sem_rs(kid);

return 0;//once all writers process is terminated..so no writer is there ...means reader will not be able to reader..data from fifo will be erased ....& then again it opens demands a reader to read to come out of block on open position

}

anubala331

**/* WRITER2 */**

#include<stdio.h>

#include<stdlib.h>

#include<fcntl.h>

#include<sys/ipc.h>

#include<unistd.h>

#include<sys/types.h>

#include<sys/sem.h>

struct sembuf a;

int sem_ac(int kid)

{

a.sem_num=0;

a.sem_op=-1;

a.sem_flg=SEM_UNDO;

return 0;

}

int sem_rs(int kid)

{

a.sem_num=0;

a.sem_op=1;

a.sem_flg=SEM_UNDO;

return 0;

}

int main()

{

int kid;

kid=semget(144,1,777|IPC_CREAT);

printf("kid=%d\n",kid);

int ret,wfd,count=0;

int buff=2;

int a=4;

int b=6;

ret=mkfifo("anu",777|IPC_CREAT);

if(ret==0)

printf("fifo created\n");

sem_ac(kid);

wfd=open("anu",O_WRONLY);//after opening ...if it finds a reader...it will write data to fifo untill its limit exceeds ...when limit came...it will allow reader to read ...then again starts wriiting to fifo..

printf("wfd=%d\n",wfd);

count=write(wfd,&buff,4);

printf("count=%d\nbuff=%d\n",count,buff);

//fd=open("anu",O_WRONLY);

//printf("fd=%d\n",fd);

close(wfd);

wfd=open("anu",O_WRONLY);//same reader will works for no. of writers

printf("wfd=%d\n",wfd);

count=write(wfd,&a,4);

printf("count=%d\na=%d\n",count,a);

close(wfd);//it will make no diffrence if i opened same fifo after closing....data will remain in that fifo......

wfd=open("anu",O_WRONLY);

printf("wfd=%d\n",wfd);

count=write(wfd,&b,4);

printf("count=%d\nb=%d\n",count,b);

close(wfd);

//sleep(1);

sem_rs(kid);

return 0;//once writer process is terminated & means reader will not be able to read...data from fifo will be erased ....& then again it opens demands a reader to read to come out of block on open position

}

anubala331

**/* WRITER3 */**

/U may open same fifo at O_RDWR mode to not to go in block on open....

#include<stdio.h>

#include<stdlib.h>

#include<fcntl.h>

#include<sys/ipc.h>

#include<unistd.h>

#include<sys/types.h>

#include<sys/sem.h>

struct sembuf a;

int sem_ac(int kid)

{

a.sem_num=0;

a.sem_op=-1;

a.sem_flg=SEM_UNDO;

return 0;

}

int sem_rs(int kid)

{

a.sem_num=0;

a.sem_op=1;

a.sem_flg=SEM_UNDO;

return 0;

}

int main()

{

int kid;

kid=semget(144,1,777|IPC_CREAT);

printf("kid=%d\n",kid);

int ret,wfd,count=0;

int buff=1;

int a=2;

int b=3;

ret=mkfifo("anu",777|IPC_CREAT);

if(ret==0)

printf("fifo created\n");

sem_ac(kid);

wfd=open("anu",O_WRONLY);//after opening ...if it finds a reader...it will write data to fifo untill its limit exceeds ...when limit came...it will allow reader to read ...then again starts wriiting to fifo..

printf("wfd=%d\n",wfd);

count=write(wfd,&buff,4);

printf("count=%d\nbuff=%d\n",count,buff);

//fd=open("anu",O_WRONLY);

//printf("fd=%d\n",fd);

close(wfd);

wfd=open("anu",O_WRONLY);//same reader will works for no. of writers

printf("wfd=%d\n",wfd);

count=write(wfd,&a,4);

printf("count=%d\na=%d\n",count,a);

close(wfd);//it will make no diffrence if i opened same fifo after closing....data will remain in that fifo......

wfd=open("anu",O_WRONLY);

printf("wfd=%d\n",wfd);

count=write(wfd,&b,4);

printf("count=%d\nb=%d\n",count,b);

close(wfd);

// sleep(1);

sem_rs(kid);

return 0;//once writer process is terminated & means reader will not be able to read...data from fifo will be erased ....& then again it opens demands a reader to read to come out of block on open position

}

anubala331

**/* READER */**

#include<stdio.h>

#include<stdlib.h>

#include<fcntl.h>

#include<unistd.h>

#include<sys/types.h>

#include<sys/ipc.h>

#include<sys/sem.h>

union semun

{

int val;

};

union semun init;

int main()

{

int kid;

printf("IN CLOSE1\n");

kid=semget(144,1,777|IPC_CREAT);

printf("kid=%d\n",kid);

//sleep(2);

init.val=1;

if(semctl(kid,0,SETVAL,init)<0)

{

printf("sem is not initialised\n");

goto OUT;

}

int i=0,fd;

int ret,count,buf,a,b;

ret=mkfifo("anu",777|IPC_CREAT);

if(ret==0)

printf("fifo created\n");

for(i=1;i<4;i++)

{

printf("i=%d*****\n",i);

fd=open("anu",O_RDONLY);//when both writer & reader r executing ...untill then ...reader can read the written data......otherwise again operating same reader will demand new writer ...that shold open now..& start wriiting data freshly...

printf("fd=%d\n",fd);

read(fd,&buf,4);//reader is able to read only upto the time in millisecond...untill there is writer..& no writting program or process is finished.....if i had made delay of 1 sec at staring of the this reader....untill then writer completes its work..& finished...no wait by writer untill fifo is full...then after that data will not be read....writer should be there if u want to read data from fifo....

printf("buf=%d\n",buf);

//sleep(1);

count=read(fd,&a,4);

printf("a=%d\n",a);

printf("count=%d\n",count);

count=read(fd,&b,4);

printf("b=%d\n",b);

printf("count=%d\n",count);

//sleep(2);

}

//sleep(1);

return 0;

OUT:

return -1;

}

anubala331

3 writers will write try to write at the same time using ./WRITER1 & ./WRITER2 & ./WRITER3 .......will be written one by one by using semaphore............& all 3 writters will be read by this single reader in for loop..........