[mrtg-developers] Re: fork problem with 2.10.8 and perl 5.6.0
Tobias Oetiker
oetiker at ee.ethz.ch
Tue Dec 2 23:31:37 MET 2003
Today Larry Fahnoe wrote:
> With the new fork code on a Red Hat 7.0 (2.2.24, perl 5.6.0) system
> I'm getting the following warnings:
>
> Use of uninitialized value in vec at /usr/bin/mrtg line 2040.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2043.
>
> The two lines are:
>
> 2040: if (vec($eout, fileno($hand[$i]), 1)) {
> 2043: next unless vec($rout, fileno($hand[$i]), 1);
>
> Tobi has already cautioned me that the new forks code is not
> compatible with perl 5.6, but since I cannot easily upgrade perl on
> the system I use for mrtg, I thought I'd add a debug() line just
> before the first of the two vec() checks to see if I could spot the
> problem:
>
> --- mrtg-2.10.8 Tue Dec 2 07:53:13 2003
> +++ mrtg Tue Dec 2 11:15:15 2003
> @@ -2037,6 +2037,7 @@
> die sprintf("ERROR: select returned %d: $!\n",
> $nfound);
> }
> for (my $i = 0; $i < $forks; $i++) {
> + debug ('fork',"Check child $i");
> if (vec($eout, fileno($hand[$i]), 1)) {
> die "ERROR: fork $i has died ahead of time?\n";
> }
>
> The resulting debug output suggests that once the child has been read,
> it should not be read again. After the first time the parent has read
> the child, subsequent calls to check on the child result in the
> uninitialized value warning. Looks to me like the eout & rout
> filehandle vectors ought to be updated once the child has been read.
> However, since I'm not familiar with the guts of the processes, I'm
> not inclined to try to fix this. Does the following output help
> someone who is qualified to fix it?
Larry
I have not looked into it yet,
but the problem may be that perl before 5.8 was not realy able to
keep filehandles in scalar variables ($x) something like *x had to
be used ...
I guess best would be if some perl 5.6 lover came up with a good
idea to 'fix' this cleanly ... one option would be to modify the
code so that it only uses the select approach in higher perl
versions ...
cheers
tobi
>
> --Larry
>
> Tue Dec 2 11:20:00 CST 2003
> --fork: Child 0 (32364) after fork
> --fork: Parent 32310 after fork of child 0
> --fork: Parent 32310 after fork of child 1
> --fork: Parent 32310 after fork of child 2
> --fork: Child 1 (32367) after fork
> --fork: Parent 32310 after fork of child 3
> --fork: Child 4 (32370) after fork
> --fork: Child 3 (32369) after fork
> --fork: Child 2 (32368) after fork
> --fork: Parent 32310 after fork of child 4
> --fork: Parent 32310 after fork of child 5
> --fork: Parent 32310 after fork of child 6
> --fork: Parent 32310 after fork of child 7
> --fork: Child 5 (32371) after fork
> --fork: Child 6 (32372) after fork
> --fork: Child 7 (32373) after fork
> --fork: Child 0 (32364) waiting to deliver
> --fork: Check child 0
> --fork: Parent reading child 0
> --fork: Check child 1
> --fork: Check child 2
> --fork: Check child 3
> --fork: Check child 4
> --fork: Check child 5
> --fork: Check child 6
> --fork: Check child 7
> --fork: Child 7 (32373) waiting to deliver
> --fork: Check child 0
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 1
> --fork: Check child 2
> --fork: Check child 3
> --fork: Check child 4
> --fork: Check child 5
> --fork: Check child 6
> --fork: Check child 7
> --fork: Parent reading child 7
> --fork: Child 2 (32368) waiting to deliver
> --fork: Check child 0
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 1
> --fork: Check child 2
> --fork: Parent reading child 2
> --fork: Child 5 (32371) waiting to deliver
> --fork: Check child 3
> --fork: Check child 4
> --fork: Check child 5
> --fork: Check child 6
> --fork: Check child 7
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 0
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 1
> --fork: Check child 2
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 3
> --fork: Check child 4
> --fork: Check child 5
> --fork: Parent reading child 5
> --fork: Check child 6
> --fork: Check child 7
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Child 1 (32367) waiting to deliver
> --fork: Check child 0
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 1
> --fork: Parent reading child 1
> --fork: Check child 2
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 3
> --fork: Check child 4
> --fork: Check child 5
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 6
> --fork: Check child 7
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Child 4 (32370) waiting to deliver
> --fork: Check child 0
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 1
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 2
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 3
> --fork: Check child 4
> --fork: Parent reading child 4
> --fork: Check child 5
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 6
> --fork: Check child 7
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Child 6 (32372) waiting to deliver
> --fork: Check child 0
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 1
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 2
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 3
> --fork: Check child 4
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 5
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 6
> --fork: Parent reading child 6
> --fork: Check child 7
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Child 3 (32369) waiting to deliver
> --fork: Check child 0
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 1
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 2
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 3
> --fork: Parent reading child 3
> --fork: Check child 4
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 5
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 6
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
> --fork: Check child 7
> Use of uninitialized value in vec at /usr/bin/mrtg line 2041.
> Use of uninitialized value in vec at /usr/bin/mrtg line 2044.
>
>
--
______ __ _
/_ __/_ / / (_) Oetiker @ ISG.EE, ETZ J97, ETH, CH-8092 Zurich
/ // _ \/ _ \/ / System Manager, Time Lord, Coder, Designer, Coach
/_/ \.__/_.__/_/ http://people.ee.ethz.ch/~oetiker +41(0)1-632-5286
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