Re: Bug in PoCo::Child when PID wraps round

sorry, I still own it.  I've just been disconnected from the world a long
time.  it will take me a while to get back to you on this but I will

> From: Tony Wildish <[email protected]>
> Date: Thu, 7 May 2009 10:58:12 +0200
> To: <[email protected]>
> Subject: Re: Bug in PoCo::Child when PID wraps round (fwd)
> 
> Hi,
> 
>  just checking one more time: is anyone looking after PoCo::Child, or is
> it orphaned?
> 
>  TIA,
>  Tony.
> 
> On Wed, 15 Apr 2009, Tony Wildish wrote:
> 
>> Hi,
>> 
>>  I sent this to the [email protected] list some time ago
>> but it looks like that list is dead. Is there someone here managing
>> PoCo::Child?
>> 
>>  Cheers,
>>  Tony.
>> 
>> ---------- Forwarded message ----------
>> Date: Tue, 24 Mar 2009 12:56:33 +0100 (CET)
>> From: Tony Wildish <[email protected]>
>> To: [email protected]
>> Subject: Bug in PoCo::Child when PID wraps round
>> 
>> Hi,
>> 
>>  we have been using PoCo::Child in a project for a while now and have just
>> uncovered a bug. The internal bookkeeping for the association of wheelIDs
>> and PIDs is wrong, with the result that when the OS PID wraps round, the
>> wrong wheelID will be given to the 'done' event.
>> 
>>  I'm using PoCo::Child version 1.39, perl 5.8.5, kernel
>> 2.6.9-78.0.8.EL.cernsmp.
>> 
>>  You can see the bug by inspection of the code. At line 192 we have:
>> 
>>         my $id = $wheel->ID;
>>         $self->debug(qq/run(): "@$cmd", wheel=$id, pid=/ . $wheel->PID);
>> 
>>         $self->{$PKG}{pids}{$wheel->PID} = $id;
>> 
>>  so the {pids} are inserted keyed on $wheel->PID. But at line 268, the
>> clean up deletes as follows:
>> 
>>         delete $self->{$PKG}{wheels}{$id};
>>         delete $self->{$PKG}{pids}{$id};
>> 
>>  so it's deleting keyed on wheel->ID, not $wheel->PID.
>> 
>>  When the PIDs wrap round, the protection in sig_child is broken by this:
>> 
>> sub sig_child {
>>     my ($kernel, $self, $pid, $rc) = @_[KERNEL, OBJECT, ARG1, ARG2];
>> 
>>         my $id = $self->{$PKG}{pids}{$pid} || "";
>> 
>>     # child death signals are issued by the OS and sent to all
>>     # sessions; we want to handle only our own children
>> 
>>         return unless $id;
>> 
>>  Because the {pids} hash had the wrong entry deleted in the cleanup, when
>> the PIDs wrap, an old $id will be found where none should be. So sig_child
>> will not return here, and will cause 'done' to be fired with the old
>> wheelID, which is plainly wrong.
>> 
>>  Also, the cleanup around line 268/269 should remove {CLOSED} and
>> {SIGCHLD} entries for the wheel too. That's less serious because it won't
>> cause a problem until wheel-IDs wrap round, which will take a lot longer,
>> but it's still a leak.
>> 
>>  Cheers,
>>  Tony.
>>