Fork wait in background process - large delay

Linux and Unix-Like Red Hat
1

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

    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