help in dinner philosophers by semaphores

[khmix]

Write a program using c language calls to Linux system to resolve the issue using the semaphores dinner philosophers to solve the problem of synchronization routines in the Linux system.
Orders, call:
fork (), getpid (), semget (), semop (), semctl ()

Dinner philosophers question states:
Five philosophers sit around a table in the ring, and by 4 chairs in front of each dish does not end with its content, and there is a fork between each tow plates, that is in front of each philosopher tow forks: one on his right and the other on his left.
Philosopher spends his life in thinking and eating from a bowl, and to be able to eat need to eat tow forks to be able to eat. After the completion of a meal, clean the philosopher tow forks to their place and ready for use again.

Write a program to:

Resolve the issue for 5 philosophers and five forks 4 chairs.
semaphores used, provided that the request by the philosopher sitting fork and eat.
Type the report describes the solution algorithm and its work program.



I wrote all my experience by semaphores but I could not form the full solution by virtue of your experience, you can:
<Modify the file with the following code to verify the requests in the top>

#include<errno.h>

#include<math.h>

#include<signal.h>

#include<stdio.h>

#include<stdlib.h>


#include<sys/types.h>

#include<sys/ipc.h>

#include<sys/sem.h>

#include<sys/time.h>


#define FALSE 0

#define TRUE 1

#define NPHIL 4 
#define NCHOPSTICKS NPHIL 

#define AVG_THINK 2.5 

#define AVG_EAT 1.5 
#define DURATION 30 



typedef union semun{

int val; 
struct semid_ds *buf;

ushort *array;

}SEM_UNION;






static int alarm_flag=FALSE;



/*------print error mesage and terminate a process------*/


void error(const char *msg)
{
fflush(stdout);

printf( "%s %d %s\n", msg ,errno,strerror(errno));

exit(0);
}

/*******signal the semaphore*******/



void my_signal(int s)
{

int status;


struct sembuf sb;
sb.sem_num=0;
sb.sem_op=1;
sb.sem_flg=SEM_UNDO;
status=semop(s,&sb,1);//s=semid
if(status<0)
{ error("In my wait,semaphore failed");}
}


/********wait on semaphore*******/
void my_wait(int s)
{
int status;
struct sembuf sb;
sb.sem_num=0;
sb.sem_op=-1;//wait1
sb.sem_flg=SEM_UNDO;

status=semop(s,&sb,1);
if(status<0)
{ error("In my wait,semaphore failed");}
}


/********think *******/
void think(int phil)
{
int duration=drand48()*1000000.0*AVG_THINK;
printf("phil %d (proc %d) thinking %d microseconds\n",phil,getpid(), duration);
usleep(duration);
}

void eat(int phil)
{
int duration=drand48()*1000000.0*AVG_EAT;
printf("phil %d (proc %d) eating %d microseconds\n",phil,getpid(), duration);
usleep(duration);
}


/*****timer*****/

void alarm_handler(sig,code,scp)

int sig;

int code;

struct sigcontext *scp;

{

alarm_flag=TRUE;

}



void set_sig_handler()

{
struct sigaction act;
act.sa_handler=alarm_handler;

#if defined_FreeBSD_
act.sa_mask=0;


#endif
act.sa_flags=SA_RESTART|SA_RESETHAND;

sigaction(SIGUSR1, &act,(struct sigaction *) NULL);

}




/******creat process*********/


int create_philososphers(const int n,int child[])
{ 
int i,status;
for (i=0;i<n;++i)
{

child[i]=0;

}

printf("creating %d philosophers\n",n);


for(i=0;i<n;++i)

{

status=fork();
if(status<0)

{
error("failed to creat philosopher \n");}

else if(status==0)
{return i-1;
}
else{ child[i-1]=status;} 
}
return -1;
}



/**********Main program*********/

int main( int argc,char *argv[])
{
int child[NPHIL],
chopstick[NCHOPSTICKS],i,status, philosopher_id=0 , left,right;
SEM_UNION arg;
key_t k;
for(i=0;i<=NCHOPSTICKS;++i)
{
k=ftok(argv[0],i);
printf("\n",argv[0],k);
chopstick[i]=semget(k,1,IPC_CREAT); 
printf("chopstick[%d] is %d\n",i,chopstick[i]);



if(chopstick[i]<0)

{error("bad sem creat");
}



arg.val=1;
status=semctl(chopstick[i],0,SETVAL,arg);
if(status<0)
{error("couldnt itinalize sem counter to 1");}
}

/*********creat semaphores******/

philosopher_id=create_philososphers(NPHIL,child);

if(philosopher_id==-1)
{
sleep(DURATION);
for(i=0;i<NPHIL;++i)
{
kill(child[i],SIGUSR1);
}
for(i=0;i<NPHIL;++i)
{
status=wait((int *)0);
if(status<0)
{
error("wait erorr detected");
}
}
for(i=0;i<NCHOPSTICKS;i++)
{
status=semctl(chopstick[i],0,IPC_RMID,0);
if(status<0)
{error("bad remove sem");}
}
}
else
{
left=philosopher_id;
right=(philosopher_id +1)%NPHIL;

set_sig_handler();
while(!alarm_flag)
{
think(philosopher_id);
if(philosopher_id & 0x1)
{
my_wait(chopstick[left]);
printf("phil %d picked up left chopstick %d\n",philosopher_id,getpid(),left);
my_wait(chopstick[right]);
printf("phil %d picked up right chopstick %d\n",philosopher_id,getpid(),right);
}
else
{
my_wait(chopstick[right]);
printf("phil %d picked up right chopstick %d\n",philosopher_id,getpid(),right);
my_wait(chopstick[left]);
printf("phil %d picked up left chopstick %d\n",philosopher_id,getpid(),left);
}

eat(philosopher_id);
if(philosopher_id & 0x1)
{
my_signal(chopstick[left]);
printf("phil %d put down left chopstick %d\n",philosopher_id,getpid(),left);
my_signal(chopstick[right]);
printf("phil %d put down right chopstick %d\n",philosopher_id,getpid(),right);
}
else
{
my_signal(chopstick[right]);
printf("phil %d put down right chopstick %d\n",philosopher_id,getpid(),right);
my_signal(chopstick[left]);
printf("phil %d put down left chopstick %d\n",philosopher_id,getpid(),left);
}
}
}
}

[lloydchristmas759]

Please be more specific on what does not work and why. You may what to read these guidelines on how to post on this forum, too:

http://cplusplus.com/articles/jLzyhbRD/

Cheers,

LloydChristmas