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Full Discussion: producer-consumer problem
Top Forums Programming producer-consumer problem Post 302268640 by joey on Tuesday 16th of December 2008 04:21:19 AM
Old 12-16-2008
producer-consumer problem
The intention of the program. Create N threads with 2 shared memories.
One shared memory to write, one shared memory to recieve.
Consumer creates 2 shared memory to share with producer.
I need H threads for the producer as well(somebody help on it..)
Also another question, would segment_id variable interfere with each other in threads?

Code:
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/shm.h>
#include <string.h>
#include <pthread.h>
#define N 10
#define H 20
pthread_t house[N];
struct message
{
               char text[10];
               int source;
                int destination;
};

void *hovig(void *param)
{
                        struct message m1;
                        int segment_id;
                        int segment_id1;
                         int size = 60;
                        struct message *shared_memory;
                        struct message1 *shared_memory1;
                        segment_id = shmget(IPC_PRIVATE,size,S_IRUSR | S_IWUSR);
                       shared_memory = (struct message *)  shmat(segment_id,NULL,0);
                        segment_id1 = shmget(IPC_PRIVATE,size,S_IRUSR | S_IWUSR);
                       shared_memory1 = (struct message *)  shmat(segment_id1,NULL,0);

                      return  (void*)(size);
}

int main()
{
                        int value = 4;
                         int i = 0;
                      for(i = 0; i < N; i++)    
                            pthread_create(&house[i], NULL,&hovig, &(value));
                    
                      pthread_join(house[i],NULL);
}

 

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LEARN ABOUT ULTRIX

shmget

shmget(2)							System Calls Manual							 shmget(2)

Name
       shmget - get shared memory segment

Syntax
       #include <sys/types.h>
       #include <sys/ipc.h>
       #include <sys/shm.h>

       int shmget (key, size, shmflg)
       key_t key;
       int size, shmflg;

Description
       The system call returns the shared memory identifier associated with key.

       A  shared  memory  identifier and associated data structure and shared memory segment of size size bytes are created for key, if one of the
       following is true:

	    The key is equal to IPC_PRIVATE.  For further information, see

	    The key does not already have a shared memory identifier associated with it, and (shmflg & IPC_CREAT ) is true.

       Upon creation, the data structure associated with the new shared memory identifier is initialized as follows:

	    The and are set equal to the effective user ID and effective group ID of the calling process.

	    The low-order nine bits of are set equal to the low-order nine bits of shmflg.  The is set equal to the value of size.

	    The and are set equal to zero (0).	The shm_ctime is set equal to the current time.

Return Values
       Upon successful completion, a non-negative integer, namely, a shared memory identifier is returned.  Otherwise, a value of -1  is  returned
       and errno is set to indicated the error.

Diagnostics
       The system call fails if any of the following is true:

       [EINVAL]       The size is less than the system-imposed minimum or greater than the system-imposed maximum.

       [EACCES]       A  shared  memory  identifier  exists for key, but operations permission, as specified by the low-order nine bits of shmflg,
		      would not be granted.  For further information, see

       [EINVAL]       A shared memory identifier exists for key, but the size of the segment associated with it is less than size and size is  not
		      equal to zero.

       [ENOENT]       A shared memory identifier does not exist for key, and (shmflg & IPC_CREAT ) is false.

       [ENOSPC]       A  shared  memory  identifier  is to be created, but the system-imposed limit on the maximum number of allowed shared memory
		      identifiers would be exceeded.

       [ENOMEM]       A shared memory identifier and the associated shared memory segment are to be created, but the amount of available  physical
		      memory is not sufficient to fill the request.

       [EEXIST]       A shared memory identifier exists for key, but ((shmflg & IPC_CREAT ) and (shmflg & IPC_EXCL )) is true.

See Also
       shmctl(2), shmop(2), ftok(3)

																	 shmget(2)
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