... hence your CB comment - with which I wholeheartedly agree :D

I've seen code such as your 2nd example fail if there's no __DATA__ section in the file.

As to the 1st example, well that's a different kettle of fish...

Given a simple script (tst.pl): 

>cat tst.pl 

use warnings;
use strict;
use Fcntl qw/:flock/;

open SELF, "< $0" or die ;
flock SELF, LOCK_EX | LOCK_NB  or die "$!";

[download]
A simple run results in... 
>perl tst.pl 
A file descriptor does not refer to an open file. at tst.pl line 7.

[download]
Re-ruuning and generating a truss log, using >truss -f perl tst.pl  > log 2>&1, the (business) end of which is... 
.
.
.
389372: open("tst.pl", O_RDONLY|O_LARGEFILE)        = 3
389372: kioctl(3, 22528, 0x00000000, 0x00000000)    Err#25 ENOTTY
389372: fstatx(3, 0x30020848, 128, 010)         = 0
389372: kfcntl(3, F_SETFD, 0x00000001)          = 0
389372: kfcntl(3, F_SETLK, 0x2FF222A0)          Err#9  EBADF
389372: access("/usr/lib/nls/msg/en_GB/libc.cat", 0)    Err#2  ENOENT
389372: access("/usr/lib/nls/msg/en_US/libc.cat", 0)    = 0
389372: _getpid()                   = 389372
389372: open("/usr/lib/nls/msg/en_US/libc.cat", O_RDONLY) = 4
389372: kioctl(4, 22528, 0x00000000, 0x00000000)    Err#25 ENOTTY
389372: kfcntl(4, F_SETFD, 0x00000001)          = 0
389372: kioctl(4, 22528, 0x00000000, 0x00000000)    Err#25 ENOTTY
389372: kread(4, "\0\001 &#65533;\007\007 I S O 8".., 4096)    = 4096
389372: lseek(4, 0, 1)                  = 4096
389372: lseek(4, 0, 1)                  = 4096
389372: lseek(4, 0, 1)                  = 4096
389372: _getpid()                   = 389372
389372: lseek(4, 0, 1)                  = 4096
389372: close(4)                    = 0
A file descriptor does not refer to an open file. at tst.pl line 7.
389372: kwrite(2, " A   f i l e   d e s c r".., 68) = 68
389372: kfcntl(2, F_GETFL, 0x00000008)          = 1
389372: kfcntl(1, F_GETFL, 0x00000008)          = 1
389372: kfcntl(2, F_GETFL, 0x00000008)          = 1
389372: close(3)                    = 0
389372: kfcntl(2, F_GETFL, 0x00000008)          = 1

[download]
We see, from 389372: open("tst.pl", O_RDONLY|O_LARGEFILE)        = 3 that the script is successfully opened on file descriptor 3.

Later, we see that the file on descriptor 3 is both open, the operations are valid and the file will/should close across an exec call... 

389372: fstatx(3, 0x30020848, 128, 010)         = 0
389372: kfcntl(3, F_SETFD, 0x00000001)          = 0

[download]
From 389372: kfcntl(3, F_SETLK, 0x2FF222A0)          Err#9  EBADF, we can see that the kernel considers FD3 to refer to a closed file - but we haven't seen a close - either explicitly (via a call to close()) or implicitly (via an intervening call to exec()).

Thus we can only conclude that there is an underlying problem with AIX.

As to a suitable answer ... I'm afraid I can't help you (aside from the fact that there is, in perl 5.8, nothing untoward mentioned in perlaix - but I expect you already know that! :-) :-((

A user level that continues to overstate my experience :-))

In reply to Re: Lightweight Solution To "Only 1 Process Running" On AIX by Bloodnok
in thread Lightweight Solution To "Only 1 Process Running" On AIX by Limbic~Region

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