[SOLVED] Sleep ()

TerryTham · 05-23-2010, 08:53 PM

Dear Linuxquestion,

Problem statement:
i have a program using fork(), Parent/Child to activate a signal by kill() function. In order to execute the process, my child function required to give a sleep() function and quit after my signal() process is done. Here is the code:

Code:

/*main*/
        
pid_t   ret;                   
int     status;         
int     role = -1;          

ret = fork();
if (ret >0) /*parent content*/
{
  printf( " Parent Process: Arm Operating (pid %d)\n", getpid() );
  signal( SIGUSR1, RWCArmWash );
  role = 0;
  pause();
  ret = wait( &status );
}
  else if (ret == 0) {
  usleep (100);
  role = 1;
  kill( getppid(), SIGUSR1 );
  sleep (55);
}

Code:

/*signal function*/
void RWCArmWash ( int sig_num )
{
  int arm=0;
  int status=4;

  libInit();
  usleep(100);

  printf( "Parent (%d) got the SIGUSR1\n", getpid() );

  arm = ARMconnectToRobot();

  arm = ARMinitializeAndCalibrate ();

  arm = ARMreturnHomePosition ();

  arm = ARMdoWash (100, 10, true, 1);
  printf("\nArm Operating, Return Code = %d\n",arm);

  usleep(100);
  libClose();
}

The code can be debug and can be executed,
-----------------------------------------------------------------

My Question:

1. Due to the ARMdoWash () function required a period of time to perform, The Sleep() function is safe to use ? does it give any trouble ?

2. Because of the ARMdoWash () function can be various of time period (depend on the work cycle of the robot arm), to always adjust the sleep () time does not giving the best idea. Can it have a better way to replace this technique ?

-----------------------------------------------------------------

Thanks for the time, would appreciated for the help

Terry

murugesan · 05-24-2010, 02:24 AM

It is also required to handle zombie process:
http://<br /> http://murugesan.webn.../zombie/<br />

I am not sure on the implemented purpose of the following

Quote:

sleep (55);

from the child process.

That can be done as per the implemented source code, provided you are working on enhancement/modification/new proposal on existing code.

This can ALSO be modified/implemented in the following way:
Parent:
ignore SIGCHLD signal
Create child Process
signal( SIGUSR1, RWCArmWash );
wait for child process using wait system call
On receiving the signal SIGUSR1 perform the action in RWCArmWash
Once done with the action in "RWCArmWash"
parent can send signal to child process
Child Process:
perform any child action
send SIGUSR1 signal to parent process
go in a infinite while loop
(wait for the signal to receive it)

This proposal is taking the information that the parent process can create only one child process.

This will go further if the parent process creates many child process and doing its job in an infinite while loop (some what similar to ftp server handling the ftp clients).

murugesan · 05-24-2010, 02:25 AM

URL mentioned earlier:
http://murugesan.webnode.com/technical/c/zombie/

TerryTham · 05-24-2010, 08:35 PM

Thanks for the reply.

i was trying to eliminate the sleep() function.
Therefore, im using variable to communicate through parent/child. Doing some pipe or some other IPC to passing variable. hopefully manage to do it.

TerryTham · 05-24-2010, 08:35 PM

Thanks for the reply.

i was trying to eliminate the sleep() function.
Therefore, im using variable to communicate through parent/child. Doing some pipe or some other IPC to passing variable. hopefully manage to do it.

eryn · 05-25-2010, 09:41 PM

The problem is solved by modifying the ARMdoWash source code to test for position in a while loop.