pthreads, I created the thread, passed a function, function never runs.

[mr_coffee]

Hi guys.

So basically my program is doing the following:
The parent: recver process is going to spawn 1 thread to read a file the child process is sending. The child process is writing a file to a message queue (IPC) and the parent process is spawning a thread and reading the message queue and will then also write the new file.
Before I tried to throw threads in this program, it was working fine with just 2 processes, 1 process writing to the message queue the other process reading and wrtiing a new file. So the message queue system isn't the issue it is the threading issue.

/* Functions */
int main( int argc, char **argv ) 
{
    int pid;
    int read_index = 0, write_index = 0, new_index = 0;
    int err;
    FILE *fp;

    /* Check for arguments */
    if ( argc < 3 ) 
    {
        /* Complain, explain, and exit */
        fprintf( stderr, "missing or bad command line arguments\n" );
        fprintf( stderr, CLIENT_USAGE );
        exit( -1 );
    }

    /* get the index for the IPC object */
    err = create_ipc( &read_index, &write_index );
    if ( err ) {
      fprintf( stderr, "create ipc error\n" );
      exit(-1);
    }

    /* create receiver process */
    if (( pid = fork() != 0 )) {
      /* parent: recver */

      /* setup the IPC channel */
      err = setup_ipc_parent( read_index, write_index,  &new_index );
      if ( err ) {
        fprintf( stderr, "rcver: error in ipc setup\n" );
	exit(-1);
      }

      
      
      /* open the output file and return the file descriptor */
      if (( fp = fopen( argv[2], "w+" )) < 0 ) {
	fprintf( stderr, "rcver: file open failure\n" );
	return -1;
      }

      /* create threads to receive the file contents */
      run_pool_threads( fp, new_index, rcv_file );
      //fclose( fp );

      /* dump the file contents */
      //rcv_file( argv[2], new_index );
      fprintf( stderr, "rcver: finished\n" );
    }
    else {
      /* childd */

      /* setup the IPC channel */
      err = setup_ipc_child( read_index, write_index, &new_index );
      if ( err ) {
        fprintf( stderr, "sender: error in ipc setup\n" );
	exit(-1);
      }



	//added
       /* open the input file and return the file descriptor */
      if (( fp = fopen( argv[1], "r" )) < 0 ) {
	fprintf( stderr, "sender: file open failure\n" );
	return -1;
      }
      
	
      /* send the file contents */
      //send_file( argv[1], new_index );
      send_file(fp,new_index);

      fprintf( stderr, "sender: finished\n" );
      }

    exit( 0 );
}

Here is the code that creates the thread, notice I'm using a structure becuase I need to pass in 2 parameters to the processes, a file descriptor and a file pointer.

int run_pool_threads( FILE *fp, int fd, void *(*threadfn)(void *))
{
  /* build, run, and manage all the sorting threads -- run rcv_file for each */
  //for now there will be only 1 thread.
  
  pthread_t thread_id;
  
   
   //We must create a structure to pass multiple arguments to the thread, such as fp and index
    thread_work_t * work_t = malloc(sizeof(thread_work_t));
     work_t->fp = fp;
     work_t->fd = fd;
  
      //creating the new thread and passing the thread_work_t structure
      pthread_create( &thread_id, NULL, threadfn, work_t);
   
 

  return 0;
}

Here is the function I'm passing to the thread, I don't beleive this ever gets ran because when I look at the output it never prints "Thread number: ". And the parent process just ends.

void *rcv_file( void *arg )
{
  printf("Thread number %ld\n", pthread_self());
  //you must cast the arg to the correct data type to access its data members
  thread_work_t *work_t;
  work_t = (struct thread_work *) arg;

  
 //create a struct to hold the msg type and message
 struct msgbuf_t msg;
 int cmd = IPC_STAT;
 
int rtrn = msgctl(work_t->fd, cmd, &BUFF);
if (rtrn == -1) 
  {
    perror("msgctl: msgctl failed");
    return EXIT_FAILURE;
  }

  printf("msg_qnum: %d\n",BUFF.msg_qnum);



  for(;;) 
  { 

	if(BUFF.msg_qnum == 0)  //there is no messages to read! so wait.
	{
	     sched_yield();
	}
	    
        //if (msgrcv(index, &msg, MSGBUF_SIZE, 0, 0) == -1) {
	if (msgrcv(work_t->fd, &msg, MSGBUF_SIZE, 0, 0) == -1) {
            perror("msgrcv");
            exit(1);
        }
	
	
	if(msg.type == MEND)
	{
	    printf("Got MEND from sender, exit\n");
	  //  fclose(fp);
	    fclose(work_t->fp);
	    break;
	}
	else if(msg.type == MTYPE)
	{
	    printf("rev: %s", msg.text);
	    //fprintf(fp,"%s",msg.text);
	    fprintf(work_t->fp,"%s",msg.text);
	     
	}
	else
	{
	    printf("WE GOT SOMTHING ELSE! LOL\n");
	}
	     
  }

     return 0;

HEre is the output:

#
cory@ubuntu:~/Documents/Operating Systems/p2$ ./p2 test2/ltest ltestOUT
KEY generated: 1090584577                                              
read and write id's: 32769                                            
sent: 3 help me, mr wizard!                                            
sent: 7 help me, mr wizard!                                            
sent: 6 help me, mr dude!                                              
sent: Found EOF
sender: finished
rcver: finished

As you can see its sending fine, but it never reads from the message queue, the thread I don't believe is ever getting ran and Im' not sure why.

ANy help would be great!

[Codeplug]

Right after calling run_pool_threads(), exit() is called - bringing the down the process and all it's threads.

You need to to either join with the thread returned by pthread_create(), or create the thread detached, then call pthread_exit() instead of exit() in main().

gg

[mr_coffee]

Thanks a lot Codeplug, worked!