Fork wait in background process - large delay Post: 302328041

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Operating Systems Linux Red Hat Fork wait in background process - large delay Post 302328041 by vishnu.priya on Tuesday 23rd of June 2009 08:24:40 AM

06-23-2009

Registered User

Fork wait in background process - large delay

hi all,

We are trying to run a process in the background and in the process we call fork ;and wait for the child process to finish .We find that the died = wait(&status); happens after 10 seconds randomly and sometimes completes in time (within 1 sec)

This behavior is seen only when the program is run as a background process. With foreground the functionality is always within 1 sec.

Can anyone please suggest the reason for this random scheduling in Linux - Operating system is CentOS

Code:

    switch ( pid = fork())
    {
        case -1:
            DbgMsg( DBG_ERR, "Cannot fork for compile!\n");
            single--;
            return -1;
        case 0:
            execvp( file, argv);
            DbgMsg(DBG_ERR | DBG_COMPILER, "Should never happen\n");
        default:
            {
waitloop:
            died = wait(&status);
            if (died == pid)
                break;
            if (died == -1) {
#if 0 /* on systems that don't map errno to __error() */
                extern int errno;
#endif

                DbgMsg(DBG_WARNING | DBG_COMPILER, "Compilation error (%s)\n", strerror(errno));
                switch (errno) {
                    case ECHILD:
                    case EINTR:
                        break;
                    default:
                        DbgMsg( DBG_WARNING, "Unexpected compilation error (%d)\n", errno);
                        goto waitloop;
                }
            }
            DbgMsg( DBG_WARNING, "Wait returned for other child %x\n", died);
            goto waitloop;
            }
    }

Thanks in advance for any help
Thanks
Vishnu

Last edited by vbe; 06-23-2009 at 12:15 PM.. Reason: added code tag + rm fancy URL...

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LEARN ABOUT BSD

exit

EXIT(2) 							System Calls Manual							   EXIT(2)

NAME

       _exit - terminate a process

SYNOPSIS

       _exit(status)
       int status;

DESCRIPTION

       _exit terminates a process with the following consequences:

       All of the descriptors open in the calling process are closed.  This may entail delays, for example, waiting for output to drain; a process
       in this state may not be killed, as it is already dying.

       If the parent process of the calling process is executing a wait or is interested in the SIGCHLD signal, then it is notified of the calling
       process's termination and the low-order eight bits of status are made available to it; see wait(2).

       The  parent  process  ID  of  all  of the calling process's existing child processes are also set to 1.	This means that the initialization
       process (see intro(2)) inherits each of these processes as well.  Any stopped children are restarted with a hangup signal (SIGHUP).

       Most C programs call the library routine exit(3), which performs cleanup actions in the standard I/O library before calling _exit.

RETURN VALUE

       This call never returns.

SEE ALSO

       fork(2), sigvec(2), wait(2), exit(3)

4th Berkeley Distribution					   May 22, 1986 							   EXIT(2)